U.S. patent application number 10/628499 was filed with the patent office on 2004-08-26 for spacer filler.
This patent application is currently assigned to Disc-O-Tech Orthopedic Technologies Inc.. Invention is credited to Beyar, Mordechay, Globerman, Oren.
Application Number | 20040167625 10/628499 |
Document ID | / |
Family ID | 33566574 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040167625 |
Kind Code |
A1 |
Beyar, Mordechay ; et
al. |
August 26, 2004 |
Spacer filler
Abstract
A kit, comprising: an expandable spacer; and a quantity of a
precursor to a bio-compatible elastic material.
Inventors: |
Beyar, Mordechay; (Caesarea,
IL) ; Globerman, Oren; (Kfar-Shmaryahu, IL) |
Correspondence
Address: |
William H. Dippert, Esq.
c/o Reed Smith LLP
29th Floor
599 Lexington Avenue
New York
NY
10022-7650
US
|
Assignee: |
Disc-O-Tech Orthopedic Technologies
Inc.
Monroe Township
NJ
|
Family ID: |
33566574 |
Appl. No.: |
10/628499 |
Filed: |
July 28, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10628499 |
Jul 28, 2003 |
|
|
|
PCT/IL02/00077 |
Jan 28, 2002 |
|
|
|
Current U.S.
Class: |
623/11.11 ;
623/17.11 |
Current CPC
Class: |
A61F 2002/30113
20130101; A61F 2002/30774 20130101; A61F 2002/30841 20130101; A61F
2002/448 20130101; A61F 2220/0058 20130101; A61F 2230/0013
20130101; A61B 17/22032 20130101; A61F 2/4611 20130101; A61F
2002/009 20130101; A61F 2002/30153 20130101; A61F 2002/30545
20130101; A61F 2002/4635 20130101; A61F 2210/0028 20130101; A61F
2230/0023 20130101; A61F 2002/2835 20130101; A61F 2002/30324
20130101; A61F 2002/30785 20130101; A61F 2/4455 20130101; A61F
2002/2817 20130101; A61F 2002/30131 20130101; A61F 2002/30484
20130101; A61F 2002/4485 20130101; A61F 2210/0019 20130101; A61F
2250/0036 20130101; A61F 2230/0091 20130101; A61B 17/1671 20130101;
A61B 17/7266 20130101; A61B 2017/00261 20130101; A61F 2002/3013
20130101; A61F 2002/30593 20130101; A61F 2250/0063 20130101; A61F
2002/30092 20130101; A61F 2002/30224 20130101; A61F 2002/305
20130101; A61F 2/30744 20130101; A61F 2/441 20130101; A61F 2/4657
20130101; A61F 2230/0019 20130101; A61F 2230/0021 20130101; A61F
2250/0039 20130101; A61F 2002/30136 20130101; A61F 2002/30405
20130101; A61F 2002/4415 20130101; A61F 2002/30082 20130101; A61F
2002/30327 20130101; A61F 2250/0014 20130101; A61F 2/446 20130101;
A61F 2002/30079 20130101; A61F 2002/3067 20130101; A61F 2250/0018
20130101; A61B 2017/320004 20130101; A61B 2017/320008 20130101;
A61F 2002/30291 20130101; A61F 2002/3055 20130101; A61F 2002/3093
20130101; A61F 2250/0043 20130101; A61F 2/30724 20130101; A61F
2002/30546 20130101; A61F 2002/30971 20130101; A61F 2002/4677
20130101; A61F 2240/001 20130101; A61B 17/1637 20130101; A61F
2002/30906 20130101; A61F 2230/0004 20130101; A61F 2002/30462
20130101; A61F 2002/4627 20130101; A61F 2/30767 20130101; A61F
2/3094 20130101; A61F 2002/30235 20130101; A61F 2002/30495
20130101; A61F 2002/30932 20130101; A61F 2002/30594 20130101; A61F
2002/4619 20130101; A61F 2230/001 20130101; A61F 2002/4638
20130101; A61F 2002/3052 20130101; A61B 2017/0256 20130101; A61F
2/442 20130101; A61F 2250/0007 20130101; A61F 2/48 20210801; A61F
2002/30154 20130101; A61F 2002/30677 20130101; A61F 2250/0012
20130101; A61F 2002/30329 20130101; A61F 2002/30617 20130101; A61F
2230/0069 20130101; A61F 2250/0097 20130101; A61F 2/30771 20130101;
A61F 2002/0086 20130101; A61F 2002/30014 20130101; A61F 2002/30507
20130101; A61F 2002/30668 20130101; A61F 2002/30052 20130101; A61F
2220/0025 20130101; A61F 2250/0037 20130101; A61F 2002/30004
20130101; A61F 2310/00017 20130101; A61F 2/28 20130101; A61F
2002/30451 20130101; A61F 2002/30604 20130101; A61F 2002/30892
20130101; A61F 2230/0006 20130101; A61F 2250/001 20130101; Y10S
606/91 20130101; A61B 17/00234 20130101; A61F 2002/30158 20130101;
A61F 2002/30616 20130101; A61F 2210/0095 20130101; A61B 2017/22034
20130101; A61F 2/02 20130101; A61F 2/4603 20130101; A61F 2002/30156
20130101; A61F 2220/0075 20130101; A61F 2250/0001 20130101; A61F
2002/30485 20130101; A61F 2002/30777 20130101; A61F 2002/4649
20130101; A61F 2250/0002 20130101; A61F 2002/30326 20130101; A61F
2002/30579 20130101; A61F 2002/30787 20130101; A61F 2002/4658
20130101; A61B 2017/320048 20130101; A61F 2210/009 20130101; A61F
2230/0026 20130101; A61F 2310/00023 20130101 |
Class at
Publication: |
623/011.11 ;
623/017.11 |
International
Class: |
A61F 002/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2001 |
IL |
141147 |
Claims
1. A kit, comprising: an expandable spacer; and a quantity of a
precursor to a bio-compatible elastic material.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of PCT
Application No. PCT/IL02/00077, filed on Jan. 28, 2002, the
disclosure of which is incorporated herein by reference. This
application is related to PCT application PCT/IB98/00523, filed on
Mar. 6, 1998, now WO 98/38918, which designated the US, the
disclosure of which is incorporated herein by reference. This
application is also related to PCT Application No. PCT/IL00/00056,
filed on Jan. 27, 2000, now WO 00/44321, and PCT Application No.
PCT/IL00/00055, filed on Jan. 27, 2000, now WO 00/44946, both of
which designate the US, the disclosures of which are incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to expandable implants,
especially for use as a spinal prosthesis.
BACKGROUND OF THE INVENTION
[0003] A common medical situation is that of a ruptured spinal
disc. Material that exits the disc may press against the spinal
cord, causing severe pain. A ruptured disc is typically treated by
a surgical procedure, in which the damaged disc is partially or
completely removed, and spinal fusion, in which at least the two
vertebrae adjacent the removed disc are fused. Several approaches
exist for spinal fusion. In one approach, the two vertebrae are
connected using a plate and/or screws. In another approach, a
spacer (also called a "cage device") is inserted between the two
vertebrae, so that bone growth into the space will fuse the
adjacent vertebra. Typically, the axis of the spacer is
perpendicular to the axis of the spine and to the plane of the
body. Sometimes the spacer includes a plurality of holes, to
encourage bone growth into the spacer. PCT publication WO 98/38918,
the disclosure of which is incorporated herein by reference,
describes a spacer that is inserted in a collapsed condition and
expanded to fill the inter-vertebral space. Another type of spacer,
exemplified by U.S. Pat. No. 5,123,926 (and others) to Pisharodi,
the disclosure of which is incorporated herein by reference,
functions like a concrete anchoring screw, in that a portion of the
spacer, usually a center portion thereof, expands by a relatively
small amount to engage the adjacent vertebrae.
[0004] U.S. Pat. No. 5,800,549, the disclosure of which is
incorporated herein by reference, describes a flexible disc
replacement that is inserted using a syringe. However, this
replacement does not fuse adjacent vertebrae, rather, it is
designed to replace the form and function of a removed
inter-vertebral disc.
[0005] One disadvantage of some of known fusion devices is that a
relatively large entry hole in the body is required to insert the
device. In some, a regular-sized surgical incision is required. In
others, a minimally invasive laproscope-size hole is required,
which typically larger than the fusion device size.
[0006] Another disadvantage of some known fusion devices is lies in
a relative complexity of procedures for delivering the devices.
[0007] Another disadvantage of some known fusion devices is a
requirement to trade/off the invasiveness of the procedure (e.g.,
do the spinal process need to be cut or the abdomen opened) and the
surface contact area between the fusion device and the bone.
Generally, if the contact surface is small, the fusion device
embeds itself in the bone and the spine slowly shrinks.
SUMMARY OF THE INVENTION
[0008] An object of some preferred embodiments of the present
invention is to provide an intra-vertebral spacer that can be
inserted using a narrow diameter needle.
[0009] An aspect of some preferred embodiments of the invention is
that a spacer having a first diameter is inserted and is then
expanded to a second, much larger diameter. Preferably, the second
diameter is greater than the first diameter by a factor of three,
four, five or more. Thus, a spacer for an inter-vertebral space of
a 12 mm may be inserted using a needle having a 4 mm (inner)
diameter. However, in some embodiments of the invention, a more
modest diameter increase is achieved, for example, between 20% and
200% or 300%.
[0010] In a preferred embodiment of the invention, the radial
expansion of the spacer is utilized to achieve a high
intra-vertebral fill, without an overly invasive surgical
procedure. Preferably, a high contact surface between the spacer
and the vertebrae is achieved.
[0011] An aspect of some embodiments of the invention relates to a
method of providing an artificial disc replacement element. In an
exemplary embodiment of the invention, a spacer is inserted between
two vertebra. Instead of encouraging bone growth through the entire
intra-vertebral space, however, an elastic material is provided or
encouraged to form in at least part of the space. In an exemplary
embodiment of the invention, the elastic material is held in place
and/or coupled to the vertebra by the spacer. In an exemplary
embodiment of the invention, the elastic material is a curable
material, for example, PMMA. Alternatively or additionally, the
elastic material is enclosed in a sac, for example, a balloon.
Optionally, the spacer impales or abuts the sac into or against the
vertebrae.
[0012] An aspect of some preferred embodiments of the invention
relates to a family of geometrical structures useful for an
expanding spacer. In a preferred embodiment of the invention, the
spacer initially comprises a structure having a narrow diameter.
When the spacer is expanded, the diameter increases. In a preferred
embodiment of the invention, the diameter of the spacer increases
at the expense of the length of the spacer, which is shortened. In
a preferred embodiment of the invention, the spacer is modified by
the expansion from a long, substantially straight object into a
shorter object have a wave-like profile. The effective diameter of
the modified spacer is that of the wave, which is significantly
greater than the initial diameter.
[0013] In a preferred embodiment of the invention, the spacer is
formed of a hollow tube having a plurality of axial slits formed on
its surface. Preferably, the slits are arranged in pairs of
parallel slits, each pair defining a spike, which spike is
preferably formed when the material between the slits is folded
perpendicular to the slits. When the tube is compressed, the spikes
fold out, preferably in the shape of an inverted "V". Typically,
though not in all embodiments of the invention, a spike comprises a
short base, one or more (usually at least two) legs or sides and
optionally a top which connects the ends of the legs. In some
embodiments, for example the inverted "V", the spike defines a peak
vertex instead of or in addition to the top.
[0014] In a preferred embodiment of the invention, a plurality of
spikes are defined around the circumference of the tube, so that
the tube "expands" in all directions. Preferably, all the spikes
have the same length. Alternatively, the length of the spike may
depend on an angular position of the spike on the circumference. In
one example, the circumference includes eight spikes per
axial-length unit of tube, the cross-section of the expanded tube
having a shape of a square, with four equal-length spikes at the
center of each side of the square and four, longer spikes, at the
four corners of the square. In a preferred embodiment of the
invention, the spacer comprises a plurality of consecutive tube
segments, each segment including one or more spikes. In one
example, a square cross-section is achieved by alternating segments
of two types, one having shorter spikes (at square sides) and the
other having longer spikes (at square corners). Alternatively, the
spike lengths are not rotationally symmetric. Alternatively or
additionally, the cross-section is not rotationally symmetric.
Alternatively or additionally, the spike lengths and/or geometry
vary as a function of the axial position and possibly also the
angular position of the spike along the spacer. In a preferred
embodiment of the invention, the spike arrangement and/or length
conforms to an expected shape of the inter-vertebral space.
[0015] A finished spacer, in accordance with some preferred
embodiments of the invention, comprises a plurality of spikes that
are provided into the body to provide a desired geometrical shape,
for example to space apart two vertebrae. The tube body parts that
do not expand, serve to interconnect the spikes, for example to
prevent them from getting lost and/or for aiding in or performing
guiding the final placement of the spikes, so that the desired
final geometry is achieved. Thus, geometric constructs other than
spikes may also be provided to a same effect.
[0016] In a preferred embodiment of the invention, each spike is
defined by two parallel slits of equal length. Alternatively, the
two slits are not of equal length. Alternatively or additionally,
the slits are not parallel, for example the slits being staggered.
Alternatively or additionally, at least some of the spikes may be
defined by more than two slits, for example three or four
slits.
[0017] In a preferred embodiment of the invention, the slits are
parallel to the axis of the tube. Alternatively, at least some of
the slits or pairs of slits are not parallel to the tube. In one
embodiments of the invention, the slits define a spiral on the
tube.
[0018] In a preferred embodiment of the invention, the extended
spikes are substantially normal to the tube axis. Alternatively, at
least some of the spikes are at an angle to the axis. In one
example, the outside spikes are angled out, for example to better
grasp surrounding bone tissue. In another example, at least some of
the spikes are angled in, for example to exert compressive forces
on a bone, for example to bring together a broken bone into which
the spacer is inserted.
[0019] In a preferred embodiment of the invention, the spikes are
substantially straight. Alternatively, at least some of the spikes
are curved, for example in a plane which includes the spike and the
tube axis and/or out of the plane. Alternatively to being curved,
at least one spike may comprise a plurality of straight portions,
each portion at an angle to another portion of the spike.
[0020] In a preferred embodiment of the invention, the spikes are
normal to the tube surface. Alternatively, at least one of the
spikes is not normal to the surface. In one example, the spikes
exit the tube surface at a parallel or near-parallel angle to the
tube surface.
[0021] In a preferred embodiment of the invention, the expanded
spacer defines a generally cylindrical shape, whose axis is
coincident with the axis of the tube. In some embodiments, the
cross-section of the expanded spacer is other than a circle, (e.g.,
a rectangle), but such a spacer preferably has a main axis which is
coincident with that of the tube. In other preferred embodiments of
the invention, however, the main axis of the expanded spacer is not
coincident with that of the tube. In one example, the axes may be
parallel, for example if when viewing the spacer cross-section all
the spikes on one side of the spacer are longer than those on an
opposite side. In another example, the axes may be non-parallel or
even non-planar. One situation where non-parallel axes are useful
is when the spacer is inserted between the vertebrae at an oblique
angle (e.g., from a posterior-lateral direction). In such an
insertion, it is still desirable that the expanded spacer be
parallel to the vertebral end-plates. In a preferred embodiment of
the invention, the spike lengths on the spacer are arranged so that
when a spacer is inserted at the oblique angle and then expanded,
the axis of the expanded spacer profile is substantially aligned
with one of the axes of the body. In some cases, two spacers are
inserted at different oblique angles, so that they better fill the
intra-vertebral space.
[0022] In a preferred embodiment of the invention, the
cross-section of the tube is circular. Alternatively, the
cross-section is that of a polygon, for example a square or a
triangle, preferably one having a same number of sides as there are
spikes around the circumference of the tube.
[0023] Alternatively to spikes being formed of a surface of a
hollow tube, the tube itself (which need not be hollow), or a
ribbon, may distort to form a wavy side profile.
[0024] An aspect of some preferred embodiments of the invention
relates to forming the tube of a material having an uneven
thickness and/or mechanical properties. In some embodiments,
mechanical characteristics of a spacer are modified after the
spacer (or a tube from which it is cut) is constructed. In other
embodiments, such mechanical characteristics may be at least partly
modified before the spacer is formed. In a preferred embodiment of
the invention, increased thickness and/or strength is provided at
points or areas where stress is concentrated when pressure is
applied to the spikes in an expanded spacer. Alternatively or
additionally, increased thickness and/or strength is provided at
points where stress is concentrated when pressure is applied to the
spikes in an expanded spacer. Alternatively or additionally,
increased thickness and/or one or more protrusions are provided on
one or more spikes to mechanically block a collapsing of the spikes
after the tube is expanded. In one example, when the spacer
comprises alternating segments of spikes, a segment may include one
or more protrusions which strengthen the spikes on an adjacent
segment. Alternatively or additionally, a lower strength and/or
pre-stressing is applied to portions of the tube which are expected
to fold (and/or stretch) when the tube is expanded. Alternatively
or additionally, variations in thickness and/or strength and/or
elasticity define portions of the spacer which better conform to
surrounding tissue. In some embodiments of the invention, the
spacer matches the geometry of the surrounding tissue. In other
embodiments, the mechanical characteristics of the spacer are
matched to the surrounding tissue, for example providing more give
where the spacer is against a hard bone.
[0025] An aspect of some preferred embodiments of the invention
relates to a inter-vertebral spacer having extending spikes, in
which at least some of the spikes have a non-V shaped profile. In a
preferred embodiment of the invention, the spikes have a flat top,
possibly with small protrusions formed thereon, so that the spikes
do not dig into the vertebrae. Alternatively or additionally, the
spikes have concave sides, so that when are stressed, they do not
collapse.
[0026] An aspect of some preferred embodiments of the invention
relates to the expansion of a spacer. In a preferred embodiment of
the invention, the expansion proceeds from one end of the spacer to
the other end, with spikes at one segment of the spacer being fully
extended before adjacent spikes are extended. Alternatively, all
the spikes are extended at the same time. Alternatively, the order
of extension is not controlled. Alternatively, first a first group
of spikes are partially extended, then, after other spikes are at
least partially extended, the first group of spikes are extended to
a greater amount. In a preferred embodiment of the invention, the
expansion of the spacer is controlled by a shaping element inserted
therein and/or using an outer collar which limits or blocks the
extension of the spikes. Possibly, the spacer includes an inner
thread to engage the shaping element. Alternatively or
additionally, the expansion is controlled by providing different
parts of the spacer with different mechanical strengths, so that
when expanded, the weaker parts expand first.
[0027] An aspect of some preferred embodiments of the invention
relates to limiting an extension dimension of the spikes.
Generally, a spike is defined by two sides of a folded strip of
material, which, together with a base defined by section of the
tube (or of its axis), form a triangle (or other shapes, as
described below). Since the length of the two material sides of the
spike are generally limited by the slits to a fixed amount, the
final extended length of the spike (i.e., the triangle height) is
inversely related to the length of the base. In some embodiments of
the invention, the spacer is axially compressed so that the length
of the base is substantially zero (excluding the thickness of the
spike itself). Alternatively, in a preferred embodiment of the
invention, an axial contraction of the tube is restricted, so that
the length of the base is significant. Preferably, a protrusion in
the spike, in one or both of the two sides of the spike, defines a
minimal distance between the sides, and hence a minimum size base
and a maximum length of a spike. Alternatively, the tube body
itself may include a mechanical limitation to its contraction. In
one example, two slits may define a section of material which, when
the tube is expanded (and axially compressed) folds upon itself or
protrudes inside the tube, rather than extending outward as a
spike. The axial contraction is thus limited by the thickness of
the folded material or by the material butting against the inside
of the tube.
[0028] Alternatively to a spike being defined by two legs, a spike
may be defined by three or more legs which are non-planar. In one
example the three legs and the base form a spike having a
tetrahedral shape. Alternatively, two legs and a top (rather than a
base) may be used to define a spike having a rectangular or an
upside-down triangle profile.
[0029] An aspect of some preferred embodiments of the invention
relates to sections cut out of the tube, to control the spacer
characteristics. In a preferred embodiment of the invention, the
missing sections are used to define an expanded spacer geometry. In
one example, a section of the tube which defines a spike is mostly
missing from the spacer. When the spacer is expanded (and axially
compressed) the two sides of the missing section advance until they
abut and further axial contraction is impossible or meets a greater
resistance. In another example, a missing section of the tube makes
one side of the spacer weaker and causes the spacer to bend in that
direction when expanded.
[0030] Alternatively or additionally, missing sections of the
spacer (tube and/or spike portions) may exist for encouraging bone
growth into the spacer.
[0031] Alternatively or additionally to missing sections of the
spacer, one or more slits may be defined in the spacer to affect
its expanded geometry, for example the geometry of the tube
section, possibly independently of the spike geometry.
[0032] An aspect of some preferred embodiments of the invention
relates to spacers which include struts, where each strut
preferably interconnects two or more spikes, when the spacer is
deployed. In a preferred embodiment of the invention, the struts
are formed from the surface of the tube which also forms the
spikes. Alternatively, the struts are provided by a second layer of
material overlaid or under-laid on the layer from which the spikes
are formed. The second layer is, in some preferred embodiments,
attached to the first layer only at points where the struts are to
be connected to the spikes, in the expanded spacer.
[0033] In a preferred embodiment of the invention, the struts
inter-connect spike peaks. Alternatively or additionally, the
struts may connect spike sides, for example at their centers.
Alternatively or additionally, the struts may connect sides with
peaks. Alternatively or additionally, the spikes may connect spike
portions with the tube itself. Preferably, although not required,
the interconnected spikes and struts form triangular or tetrahedral
shapes.
[0034] In a preferred embodiment of the invention, a single strut
interconnects two spikes. In some embodiments, a single spike may
be connected to more than one strut, for example, in a spacer
having four spikes around its circumference, four struts may be
provided to form a ring which encloses the spacer cross-section.
Alternatively or additionally to radially interconnecting spikes,
the struts may axially inter-connect spikes, for example forming a
line of struts which is parallel to the axis of the spacer.
Substantially any spike interconnection pattern may be provided,
for example, a spiral strut path which interconnects spikes to
define a spiral pattern on the expanded spacer (e.g., around the
axis of the spacer).
[0035] In a preferred embodiment of the invention, the struts are
parallel to the outline of the cross-section of the spacer, for
example defining a rectangle if the spacer has a rectangular
cross-section. In other embodiments, however, such parallelism is
not required. For example, the struts may define a rectangle which
is rotated at 45.degree. relative to the spacer cross-section.
[0036] In a preferred embodiment of the invention, the struts are
arranged in a radial symmetry. Alternatively or additionally, the
struts are arranged in an axial symmetry. Alternatively, the struts
are arranged asymmetrically. Preferably, the pattern of
strut-asymmetry matches and/or is aligned with a pattern of spike
asymmetry. Alternatively, the patterns do not match and/or are not
aligned.
[0037] In a preferred embodiment of the invention, the struts
structurally limit relative movement between spikes and/or spacer
portions, preferably, by resisting movement of two points connected
by spikes towards (and/or away from) each other. Alternatively or
additionally, the struts may provide other structural support, for
example, to limit relative outward movement of two points, to limit
expansion of a portion of the spacer, to limit certain deformations
of the spacer under stress and/or to limit spike extension.
[0038] Alternatively or additionally to using struts, one or more
of these strut-functions may be provided by wires. As used herein
the differences between wires and struts (both of which are
examples of inter-connecting elements), are mainly in their
relative rigidity and thicknesses. Additionally, struts usually
maintain the same rigid configuration when the spacer is expanded
and when it is collapsed (or folded at pre-defined points), while
wires may change their configuration, for example being folded when
the spacer is collapsed and being extended when the spacer is
expanded. Alternatively or additionally to directly structural
functions, the struts and/or wires may be used to effect a desired
contact surface, for example, to enhance fusion with bone or to
limit embedding or sinking of spikes in the surrounding bone.
[0039] In a preferred embodiment of the invention, the
inter-connecting elements have a fixed cross-section.
Alternatively, the cross-section and/or the mechanical properties
may vary along the length, width and/or thickness of an
inter-connecting element. Possibly, different inter-connecting
elements (e.g., different struts) may have different geometries
and/or material properties.
[0040] An aspect of some preferred embodiments of the invention
relates to locking mechanisms for an axially contracting spacer. In
a preferred embodiment of the invention, the locking mechanisms
lock an inner bolt of the spacer against an outer portion of the
spacer. Preferably, the locking is activated by retracting a member
used to contract the spacer. Alternatively, the locking is
activated by advancing and/or rotating the member. In a preferred
embodiment of the invention, the locking mechanism and/or a member
freeing mechanism is primed by the spacer completing its axial
contraction.
[0041] An aspect of some preferred embodiments of the invention
relates to a tissue excavation tool, especially for disc removal.
In a preferred embodiment of the invention, the tool comprises an
elongate member having at the end thereof an expandable portion
comprising a plurality of spikes. The tool may be inserted into the
spine at a small diameter and the spikes are then extended. Tissue
excavation is preferably performed by rotating the tool, so the
spikes disintegrate the disc tissue. Preferably, the tool is hollow
so the disintegrated tissue may be vacuumed out of the intra-verbal
space. Alternatively or additionally, the tool may be bent, to
reach locations out of line with from the entry point of the tool.
Alternatively or additionally, a stylet is inserted into a hollow
of the tool, to guide it to various locations in the
inter-vertebral space. The tool is preferably formed of metal,
however, it may be formed of other materials, for example plastic.
The rotational speed of the tool may be, low, for example 100 RPM
or high, for example 3000 RPM. In some embodiments the spikes have
sharpened edges, while in other embodiments such sharpened edges
are not required and/or not provided.
[0042] An aspect of some preferred embodiments of the invention
relates to using an expandable tube-spikes structure for other
uses, for example for bone anchoring, for tooth implanting, for
supporting fractured bones, including for example long, short and
bent bones, as an bone anchor (preferably inside the medullar
channel) for a joint, such as a hip or finger joint, and/or for
gradually modifying bone structure. In a preferred embodiment of
the invention, the spacer is inserted into a bone to be modified
and/or supported using a needle. In one example, the spacer is
inserted in an unexpanded configuration and once the bone segments
are aligned, for example using x-ray imaging techniques, the spacer
is expanded to grasp the bone segments and possibly urge them
together. In a preferred embodiment of the invention, the spacer
may be removed once the bone is knit by collapsing the spacer and
removing it using a thin cannula.
[0043] An aspect of some preferred embodiments of the invention
relates to controlling the configuration of an implanted spacer
using externally applied power and/or controls. In a preferred
embodiment of the invention, the expansion of the spacer is
increased and/or decreased responsive to such externally applied
power and/or controls signals. Preferably, such increase and/or
decrease is used to gradually bend, straighten, lengthen, shorten
twist and/or otherwise model bones in which the spacer is
implanted, for example ribs or leg bones. In one example, bones are
bent and/or straightened, using a spacer whose bend is related to
its axial length. Preferably, a spacer for bone modeling
automatically extends/distorts by a predetermined amount each day,
in response to an outside command or using a ratchet mechanism.
[0044] An aspect of some preferred embodiments of the invention
relates to using an implanted spacer to report on internal
physiological parameters. In one example, the spacer reports a
degree of bone ingrowth, such as to enable a treating physician to
monitor the healing process. In another example the spacer reports
applied torque and pressure, such as to enable a treating physician
to assess structural problems of the bone and/or the spacer. In a
preferred embodiment of the invention, a sensor, for example a
silicon pressure or strain sensor) is integrated with the spacer.
Alternatively, the body of the spacer itself provides at least some
of the sensing, for example, by vibration modes of the spacer
changing responsive to bone ingrowth and/or by tracking (using
medical imaging techniques) changes in the configuration of the
device and especially configuration changes in designated pressure
sensitive portions thereof. Such a pressure sensitive portion, can
be, for example, a hollow bubble of metal which is compressed by
external pressure from the growing bone. The shape of the bubble
may be determined, for example using x-ray imaging or by analyzing
resonance characteristics of the spacer.
[0045] There is thus provided in accordance with a preferred
embodiment of the invention, an expandable spacer, comprising:
[0046] an axial tube having a surface, a proximal end, a distal end
and a length,
[0047] wherein, said surface defines a plurality of slits, said
plurality of slits defining at least two axially displaced
extensions, such that when said tube is axially compressed, said
extensions extend out of said surface and define a geometry of an
expanded spacer.
[0048] Preferably, said at least two axially displaced extensions
comprises at least three extensions, which three extensions extend
in at least three different directions from said tube.
Alternatively or additionally, said at least two axially displaced
extensions comprises at least four extensions, which four
extensions extend in at least four different directions from said
tube.
[0049] In a preferred embodiment of the invention, said slits are
straight. Alternatively or additionally, said slits are curved.
[0050] In a preferred embodiment of the invention, said slits are
narrow.
[0051] In a preferred embodiment of the invention, said slits have
a non-trivial width for at least part of their length.
[0052] In a preferred embodiment of the invention, said slits are
substantially parallel to said tube axis.
[0053] In a preferred embodiment of the invention, said slits are
not parallel to said tube axis.
[0054] In a preferred embodiment of the invention, said slits are
arranged in pairs of same length.
[0055] In a preferred embodiment of the invention, said slits are
arranged in pairs of different lengths.
[0056] In a preferred embodiment of the invention, slits associated
with one extension axially overlap slits associated with a second,
axially displaced, extension.
[0057] In a preferred embodiment of the invention, said proximal
end of said tube defines a proximal end-cap, which end-cap extends
outside of a volume defined by the geometry of said extended
extensions.
[0058] In a preferred embodiment of the invention, said distal end
of said tube defines a distal end-cap, which end-cap extends
outside of a volume defined by the geometry of said extended
extensions. Alternatively, at least one of said extensions is flush
with said proximal end of said tube. Alternatively, at least one of
said extensions is flush with said distal end of said tube.
[0059] In a preferred embodiment of the invention, the spacer
comprises at least one spur axially extending from said spacer, to
engage tissue adjacent said spacer. Preferably, said at least one
spur comprises at least two spurs axially extending from said
spacer.
[0060] In a preferred embodiment of the invention, the spacer
comprises an inner bolt. Preferably, said inner bolt has a smooth
exterior. Alternatively, said inner bolt has a threaded
exterior.
[0061] In a preferred embodiment of the invention, said bolt has a
base, which base has an external diameter greater than an inner
diameter of said tube, such that said base restricts axial motion
of tube in one direction relative to the bolt.
[0062] In a preferred embodiment of the invention, said bolt has a
head, which head locks against at least one end of said tube, to
prevent axial expansion of said tube. Preferably, said head is
adapted to engage at least one protrusions extending from said tube
toward said bolt head. Alternatively, said head comprises at least
one protrusions extending from said head toward said tube, to
engage said tube. Alternatively, said head comprises a flange,
flared to have an outer diameter greater than an inner diameter of
said tube.
[0063] In a preferred embodiment of the invention, said bolt is
adapted to engage a pole element for holding said bolt during
deployment of said spacer. Preferably, said bolt has an inner
thread for engaging said pole element. Alternatively, said bolt
mechanically engages said pole element as long as a head of said
bolt is constrained by said tube.
[0064] In a preferred embodiment of the invention, said spacer
comprises a plurality of segments, each segment defining one or
more extensions that extend from said spacer. Preferably, said
segments comprises at least two segment types, each segment type
defining extensions that extend in different directions relative to
said tube. Preferably, said two segment types comprises a
horizontal segment defining two extensions that extend along a line
and a segment defining four extensions that extend at about
.+-.45.degree. to said two extensions.
[0065] In a preferred embodiment of the invention, an extension
direction of at least one of said at least two extensions is normal
to said tube.
[0066] In a preferred embodiment of the invention, an extension
direction of at least one of said at least two extensions defines a
sharp angle with said tube axis, in a plane containing said tube
axis.
[0067] In a preferred embodiment of the invention, at least one of
said at least two extensions does not extend along a direction
perpendicular to said tube.
[0068] In a preferred embodiment of the invention, at least one of
said at least two extensions has, in a plane containing said tube
axis, a profile of a triangle, with the tip pointed away from said
tube.
[0069] In a preferred embodiment of the invention, at least one of
said at least two extensions has, in a plane containing said tube
axis, a curved profile.
[0070] In a preferred embodiment of the invention, at least one of
said at least two extensions has, in a plane containing said tube
axis, a profile that narrows and then widens, along a direction
away from the tube.
[0071] In a preferred embodiment of the invention, at least one of
said at least two extensions has, in a plane perpendicular to said
tube axis, a profile that narrows, along a direction away from the
tube.
[0072] In a preferred embodiment of the invention, at least one of
said at least two extensions has, in a plane perpendicular to said
tube axis, a profile that narrows and then widens, along a
direction away from the tube.
[0073] In a preferred embodiment of the invention, at least one of
said at least two extensions has, in a plane perpendicular to said
tube axis, a uniform profile.
[0074] In a preferred embodiment of the invention, at least one of
said at least two extensions has, a pointed top profile.
Alternatively, at least one of said at least two extensions has, a
top profile substantially the same size as a base of said
extension. Alternatively, at least one of said at least two
extensions has, a top profile substantially the larger that a base
of said extension.
[0075] In a preferred embodiment of the invention, said extensions
are unevenly distributed along said axis. Alternatively, said
extensions are evenly distributed along said axis.
[0076] In a preferred embodiment of the invention, said extensions
are unevenly distributed along a circumference of said tube.
Alternatively, said extensions are evenly distributed along a
circumference of said tube.
[0077] In a preferred embodiment of the invention, said different
ones of said extensions have different geometries. Alternatively or
additionally, said extensions are distributed in a spiral pattern.
Alternatively or additionally, said tube axis is coaxial with an
axis of said expanded geometry.
[0078] In a preferred embodiment of the invention, said tube axis
is parallel to an axis of said expanded geometry.
[0079] In a preferred embodiment of the invention, said tube axis
is not-parallel to an axis of said expanded geometry. Preferably,
said tube axis and said expanded geometry axis are designed for
oblique insertion of a spacer to be aligned, in its expanded state
with vertebra.
[0080] In a preferred embodiment of the invention, said spacer has
an expanded geometry cross-section of a circle.
[0081] In a preferred embodiment of the invention, said spacer has
an expanded geometry cross-section of a rectangle.
[0082] In a preferred embodiment of the invention, a cross-section
of said expanded geometry varies along an axis of said expanded
geometry.
[0083] In a preferred embodiment of the invention, a cross-section
diameter of said expanded geometry varies along an axis of said
expanded geometry. Preferably, said cross-section is rectangular
and wherein said cross-sectional diameter increases along said
expanded geometry axis.
[0084] In a preferred embodiment of the invention, a cross-section
diameter of said tube varies along an axis of said tube.
Alternatively or additionally, a cross-section of said tube varies
along an axis of said tube.
[0085] In a preferred embodiment of the invention, said tube has a
circular cross-section.
[0086] In a preferred embodiment of the invention, said tube has an
elliptical cross-section.
[0087] In a preferred embodiment of the invention, said tube has a
rectangular cross-section. Alternatively or additionally, said tube
axis is bent, when the spacer is unexpanded.
[0088] In a preferred embodiment of the invention, said tube axis
is straight when the spacer is unexpanded. Alternatively or
additionally, said tube axis is bent when the spacer is
expanded.
[0089] In a preferred embodiment of the invention, said tube axis
is straight when the spacer is expanded.
[0090] In a preferred embodiment of the invention, the spacer
comprises a ratchet mechanism to maintain said spacer in an
expanded configuration.
[0091] In a preferred embodiment of the invention, the spacer
comprises at least one portion of said spacer that prevents axial
contraction of said spacer. Preferably, said at least one portion
comprises a pair of tabs that abut when the spacer is axially
contracted. Alternatively, said at least one portion comprises a
strip that folds and forms a thickness between two opposing sides
of said spacer, preventing the opposing sides from meeting.
[0092] In a preferred embodiment of the invention, the spacer
comprises at least protrusion on at least on of said extensions, to
prevent collapsing of said extension.
[0093] In a preferred embodiment of the invention, the spacer
comprises at least protrusion on at least on of said extensions, to
interlock said two extensions.
[0094] In a preferred embodiment of the invention, the spacer
comprises at least one interconnecting element for interconnecting
said extensions when the extensions are expanded. Preferably, said
interconnecting element comprises a flexible wire. Alternatively,
said interconnecting element comprises a substantially rigid
strut.
[0095] In a preferred embodiment of the invention, at least one of
said extensions comprises only bending joints.
[0096] In a preferred embodiment of the invention, at least one of
said extensions comprises at least one twisting joint.
[0097] In a preferred embodiment of the invention, at least one of
said extensions comprises a lift-up-extension in which a
significant axial section of the tube is lifted away from said tube
to form said expanded geometry.
[0098] In a preferred embodiment of the invention, at least one of
said extensions comprises at least two legs that are coupled by a
extension top.
[0099] In a preferred embodiment of the invention, at least one of
said extensions comprises at least three legs that are coupled by a
extension top.
[0100] In a preferred embodiment of the invention, at least one of
said extensions comprises at least four legs that are coupled by a
extension top. Alternatively or additionally, at least one of said
extensions comprises at least two legs, which legs are aligned with
the tube axis. Alternatively or additionally, a plurality of
annealed locations are provided on said spacer to assist in
expansion of said spacer. Alternatively or additionally, a
plurality of etched locations are provided on said spacer to assist
in expansion of said spacer. Alternatively or additionally, a
plurality of holes are provided on said spacer to assist in
expansion of said spacer. Preferably, said holes distribute stress
in said spacer.
[0101] In a preferred embodiment of the invention, said spacer is
annealed as a unit.
[0102] In a preferred embodiment of the invention, said spacer
comprises means for changing the axial length of the spacer over
time, after the spacer is implanted. Alternatively or additionally,
said spacer is formed of metal. Alternatively, said spacer is
formed of plastic.
[0103] In an alternative preferred embodiment of the invention,
said spacer is formed of a combination of distinct zones of
different materials.
[0104] In a preferred embodiment of the invention, said spacer
comprises an elastic material, which is elastically deformed by the
extension deformation. Alternatively or additionally, said spacer
comprises a plastic material, which is plastically deformed by the
extension deformation. Alternatively or additionally, said spacer
comprises a super-elastic material, which is super-elastically
deformed by the extension deformation. Alternatively or
additionally, said spacer comprises a shape-memory material.
[0105] In a preferred embodiment of the invention, said spacer is
adapted to be axially deformed under axial pressures of over 20 Kg.
Alternatively or additionally, said spacer is adapted to be axially
deformed under axial pressures of over 30 Kg. Alternatively or
additionally, said spacer is adapted to be axially deformed under
axial pressures of over 50 Kg. Alternatively or additionally, said
spacer is adapted to be axially deformed under axial pressures of
over 70 Kg. Alternatively or additionally, said spacer is adapted
to be axially deformed under axial pressures of over 90 Kg.
[0106] In a preferred embodiment of the invention, said spacer is
adapted to remain expanded in a vertebra of an active human, when
placed with the tube axis perpendicular o a spine of said human.
Alternatively or additionally, said tube has a cross-sectional
diameter smaller than 2 times the maximal cross-sectional diameter
of said expanded geometry.
[0107] In a preferred embodiment of the invention, said tube has a
cross-sectional diameter smaller than 4 times the maximal
cross-sectional diameter of said expanded geometry.
[0108] In a preferred embodiment of the invention, said expanded
geometry is sized to fit between two human vertebrae.
[0109] In a preferred embodiment of the invention, said extensions
have tips and wherein said tips has a surface fill factor of at
least 20% relative to the contact surface of a target vertebra with
the spacer geometry.
[0110] In a preferred embodiment of the invention, said extensions
have tips and wherein said tips has a surface fill factor of at
least 40% relative to the contact surface of a target vertebra with
the spacer geometry.
[0111] In a preferred embodiment of the invention, said extensions
have tips that contact a surface of target vertebra and wherein
said tips has a surface fill factor of at least 60% relative to the
contact surface of the target vertebra with the spacer
geometry.
[0112] In a preferred embodiment of the invention, said expanded
geometry covers at least 40% of the surface of a target vertebra,
previously contacting a disc.
[0113] In a preferred embodiment of the invention, said expanded
geometry covers at least 60% of the surface of a target vertebra,
previously contacting a disc.
[0114] In a preferred embodiment of the invention, said expanded
geometry covers at least 80% of the surface of a target vertebra,
previously contacting a disc.
[0115] There is also provided in accordance with a preferred
embodiment of the invention, a spacer, comprising:
[0116] an elongate body having a surface and having a maximum
cross-section at a portion thereof; and
[0117] a plurality of extensions radially extending from said
body,
[0118] wherein, said extensions are dense on at least 40% of said
body, including said portion, such that at least 50% of a surface
area of said body is covered by extensions, wherein said dense
extensions define a cross-section having a diameter at least three
times a diameter of said body cross-section and wherein said
extensions are formed of said surface. Preferably, said extensions
are dense on at least 50% of said body. Alternatively or
additionally, said extensions are dense on at least 70% of said
body.
[0119] In a preferred embodiment of the invention, a spacer is
coated with a bio-active coating. Preferably, said bio-active
coating retards bone ingrowth. Alternatively or additionally, said
bio-active coating promotes bone ingrowth.
[0120] In a preferred embodiment of the invention, said extensions
comprises spikes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0121] The present invention will be more clearly understood from
the following detailed description of the preferred embodiments of
the invention and from the attached drawings, in which:
[0122] FIG. 1A shows a flat projection of an expandable spacer, in
an un-expanded configuration thereof, in accordance with a
preferred embodiment of the invention;
[0123] FIG. 1B shows a perspective view of the spacer of FIG.
1A;
[0124] FIG. 1C shows both an axial flat projection and a front flat
projection of the spacer of FIG. 1A, in an expanded configuration
thereof;
[0125] FIG. 1D shows a perspective view of the spacer of FIG. 1A,
in an expanded configuration thereof;
[0126] FIGS. 2A-2D illustrate a process of inserting and expanding
a spacer, in accordance with a preferred embodiment of the
invention;
[0127] FIGS. 2E-2G illustrate methods of controlling an expansion
of a spacer, in accordance with preferred embodiments of the
invention;
[0128] FIGS. 2H-2J illustrate removable and/or adjustable spacers,
in accordance with preferred embodiments of the invention;
[0129] FIGS. 2K-2L illustrate shaped tips for controlling the
expansion of a spacer, in accordance with a preferred embodiment of
the invention;
[0130] FIG. 2M is a spread layout of a spacer including an
expansion limiting wire, in accordance with a preferred embodiment
of the invention;
[0131] FIG. 2N is a spread layout of a self-bending spacer, in
accordance with a preferred embodiment of the invention;
[0132] FIG. 2O illustrates a spacer having an internal end-cap, in
accordance with a preferred embodiment of the invention;
[0133] FIG. 2P illustrates a spacer having a collapsed axis which
is not parallel to an expanded axis of the spacer, in accordance
with a preferred embodiment of the invention;
[0134] FIGS. 3A-3E are axial views of spacers with struts in
accordance with preferred embodiments of the invention;
[0135] FIGS. 3F-3M illustrate one method of providing struts
between spikes, in this example struts which ring the spacer at the
spike peaks;
[0136] FIG. 4A shows a flat projection of a spacer having a square
profile when expanded, in an un-expanded configuration, in
accordance with a preferred embodiment of the invention;
[0137] FIG. 4B shows both an axial flat projection and a front flat
projection of the spacer of FIG. 4A, in an expanded configuration
thereof;
[0138] FIG. 4C is a perspective view of the spacer of FIG. 4A, in
an expanded configuration;
[0139] FIG. 4D illustrates a variation of the spacer of FIGS.
4A-4C, in which spikes only extend in six transaxial directions and
not eight, in accordance with a preferred embodiment of the
invention.
[0140] FIG. 4E illustrates a spacer configuration in which one
spacer is expanded within another spacer;
[0141] FIG. 5 illustrates a spacer in which slits are formed on the
spacer in a spiral pattern;
[0142] FIGS. 6A-6V illustrate variants of spikes and/or spike
orientations, in accordance with alternative preferred embodiments
of the invention;
[0143] FIGS. 6W and 6X illustrate spikes having portions which
twist when the spacer is expanded;
[0144] FIGS. 6XA-6XC illustrate a flat-top spike in accordance with
a preferred embodiment of the invention;
[0145] FIGS. 6XD-6XH illustrate a flat-top spike in accordance with
another preferred embodiment of the invention;
[0146] FIGS. 6XI-6XL illustrate a method of removing portions of a
spacer, to achieve a desired spike shape;
[0147] FIG. 7 illustrates protrusions on a spacer portion, in
accordance with a preferred embodiment of the invention;
[0148] FIGS. 8A-8B illustrates spacers for which axial shrinkage of
the spacer is limited by the design of a tube portion of the
spacer, in accordance with preferred embodiments of the
invention;
[0149] FIG. 9A illustrates an excavating tool, in accordance with a
preferred embodiment of the invention;
[0150] FIG. 9B illustrates the tool of FIG. 9A, in a bent
configuration, in accordance with a preferred embodiment of the
invention;
[0151] FIGS. 10A-10C illustrate an expandable bone implant, in
accordance with a preferred embodiment of the invention;
[0152] FIG. 11 is an exploded view of a dental implant device in
accordance with a preferred embodiment of the invention;
[0153] FIGS. 12A-12C illustrate the use of an axially contracting
tissue fastener, in accordance with a preferred embodiment of the
invention;
[0154] FIGS. 13A-13C illustrate a method of controlling the
expansion of a spacer, in accordance with a preferred embodiment of
the invention;
[0155] FIGS. 14A and 14B illustrate a fin based locking mechanism
in which one or more locking fins spring out from a bolt to engage
a spacer, in accordance with a preferred embodiment of the
invention;
[0156] FIGS. 15A and 15B illustrate a locking mechanism similar to
that of FIGS. 14A-14B, utilizing plastic deformation, in accordance
with a preferred embodiment of the invention;
[0157] FIGS. 16A-16F illustrate a locking mechanism utilizing an
expanding flange, in accordance with a preferred embodiment of the
invention;
[0158] FIGS. 17A-17C illustrate an alternative locking mechanism in
which fins on a spacer engage a bolt inside of the spacer, in
accordance with a preferred embodiment of the invention;
[0159] FIGS. 18A-18D illustrate a locking mechanism in which fins
on a bolt are extended when a pole element of the bolt is
retracted, in accordance with a preferred embodiment of the
invention;
[0160] FIGS. 19A-19C illustrate a ring-based locking mechanism, in
accordance with a preferred embodiment of the invention;
[0161] FIG. 20 illustrates a portion of a spacer, in which a
plurality of banded areas indicate portions to be annealed, to
assist in the expansion of the spacer, in accordance with a
preferred embodiment of the invention; and
[0162] FIGS. 21A and 21B illustrate spike designs for
stress-release, in accordance with a preferred embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0163] Basic Spacer (Cage) Description
[0164] FIG. 1A shows a flat projection of an expandable spacer 20,
in an un-expanded configuration thereof, in accordance with a
preferred embodiment of the invention. FIG. 1B is a perspective
view of spacer 20. Spacer 20 comprises an elongate hollow object
22, such as a tube, having a plurality of spikes 24 defined thereon
(in a flattened form), each spike being defined by a pair of slots
26. In a preferred embodiment of the invention, the cross-section
of tube 22 is a circle, as shown in an axial projection 36 of the
spacer. In the embodiment shown in FIG. 1A, tube 22 includes
alternating spike segments 28 and non-spike segments 30. At one end
of the tube, an end-cap 34 is preferably defined. In a preferred
embodiment of the invention, end-cap 34 is hollow. Alternatively,
end-cap 34 is solid, but preferably comprising a porous material or
including holes, to enhance bone ingrowth. Alternatively or
additionally to end-cap 34, spacer 20 is attached to the end of a
tube, such that only a portion of the tube, preferably an end
portion, has slits defined therein.
[0165] FIGS. 1C-1D show spacer 20 in an expanded configuration,
FIG. 1C using a flat projection (side and axial) and FIG. 1D using
a perspective view. When expanded, spikes 28 extend outwards and
tube 22 is axially compressed. Non-spike segments 30 and end-cap(s)
34 preferably do not distort. As can be seen in the figures, a
considerable expansion in diameter is achieved, for example a five
fold expansion. In addition, a considerable axial contraction is
achieved, as evidenced by comparing the thickness of a spike 24 in
FIG. 1C (38) with FIG. 1A (28).
[0166] Although spacer 20 has been described as including non-spike
portions, it should be appreciated that in some preferred
embodiments of the invention no such non-spike portions are
defined, for example, if the slits are interleaved, as shown by the
example of a dotted line 35 in FIG. 1A.
[0167] In a preferred embodiment of the invention, tube slits 26
include round holes, for example holes 32, at their ends.
Preferably, these holes are defined to reduce the propagation of
stress and/or mechanical failure in tube 22. Alternatively or
additionally, these holes are defined to weaken the end of the slit
so that when spacer 20 is axially collapsed, spikes 28 will
preferentially fold out at the ends of the slits. Alternatively or
additionally, slits 26 may include holes 33 at their center (the
apex of spikes 28), to encourage folding of the spike at the
location of the hole.
[0168] The above is a description of a limited subset of spacers,
further variations are defined below.
[0169] Basic Delivery Method
[0170] FIGS. 2A-D illustrate a process of inserting and expanding
spacer 20. In FIG. 2A, a damaged disc 54 is located in an
inter-vertebral space 55, between a vertebra 50 and a vertebra 52.
Typically, before inserting a spacer between the two vertebra, disc
54 is partially or completely removed. Preferably, disc 54 is
removed using a minimally invasive technique, preferably using only
a thin needle 56, for example as described below with reference to
FIGS. 9A and 9B. Alternatively, a laproscopic approach is used, for
example as described in WO 98/38918, preferably taking care to
minimize trauma to the patient.
[0171] In a preferred embodiment of the invention, all the
cartilaginous end plate is removed, as known in the art, however,
this is not required. Alternatively or additionally, a plurality of
holes are formed in the endplate and/or the vertebra itself, to
promote bone growth.
[0172] In FIG. 2B, the disc has been removed and a spacer 20 is
inserted into inter-vertebral space 55, in an un-expanded
configuration. In a preferred embodiment of the invention, spacer
20 is mounted on- or formed at the end of an elongate member 60.
Preferably, spacer 20 is inserted using a syringe or in an
"over-tube" which may be retrieved, once the spacer is inserted.
Alternatively or additionally, spacer 20 is inserted using X-Ray
guidance, to avoid damaging the spinal cord.
[0173] In FIG. 2C, spacer 20 is in the process of being radially
expanded (and axially shortened). A portion 62 of spacer 20 is
expanded, while a length 64 of spacer 62 is not yet expanded.
[0174] In FIG. 2D, spacer 20 is radially expanded over its entire
expansion length and it fills inter-vertebral space 55. In a
preferred embodiment of the invention, a fixing material, such as a
bone slurry or a setting fixing compound is provided into
inter-vertebral space 55, in order to encourage fusion between
vertebra 50 and vertebra 52. In the case of a bone slurry, bone
chips or bone powder, such setting may require a week or so of bed
rest. Preferably, spacer 20 is stiff enough to maintain its shape
until the bone sets, so that little or no bed rest is required.
Alternatively or additionally, at least some of the required
stiffness is provided by the fixing material. Alternatively or
additionally, the fixing material serves as a space filler and/or
to provide compressive strength. Alternatively or additionally, to
injecting a fixing material or as part of the fixing material,
growth hormones, enzymes, anti-bacterial pharmaceuticals,
anti-inflammatory compounds and/or other bio-active materials may
be injected into space 55, to encourage fusion and/or another
desired effect. Preferably, the filler material fills the entire
space 55 and is contiguous.
[0175] OrthoLogic Inc., of Tempe, produces a device named
"SpinaLogic", that appears to promote healing by magnetic field
generation. In some embodiments of the invention, the spacer
comprises or includes magnetic materials, such as ferrite
(preferably encapsulated or coated) for controlling the field lines
of the magnetic fields. Alternatively or additionally, the
SpinaLogic device may be used to promote healing in a standard
fashion.
[0176] One of the PCT applications mentioned above as being filed
on even date, describes an exemplary disc access and spacer
delivery system.
[0177] Ingrowth Control
[0178] In a preferred embodiment of the invention, the bone slurry
comprises bone chips, for example spherical or cubic or flat
rectangular shaped chips. Such chips may be generated for example
using a small oscillating saw and/or osteotome. A pituitary forceps
or bone impactor-holder may be used to push the bone chips through
a delivery tube, typically but not necessarily a same tube through
which the spacer is advanced. In an exemplary application the tube
has an inner diameter of 6 mm, so the bone chips should have a
largest extent of 5.9 mm.
[0179] Exemplary bone sources can be a tricortical autologous crest
bone graft, a fibular bone bank graft or a cadaver bone.
Alternatively or additionally, the bone slurry can include a mesh,
hydroxylapatite and/or ossification accelerating material, such as
known in the art. The bone chips may be selected to fit between
spikes and through spike sides of a particular spacer used.
[0180] In an alternative preferred embodiment of the invention, the
fixing material is provided through member 60, rather than through
an enclosing tube, as in some embodiments, no such outer tube is
provided and member 60 serves as such an outer tube instead, for at
least some of the activities in the spine. Alternatively, it is
provided using a syringe. It will be appreciated from viewing FIG.
1D that in the expanded configuration, spacer 20 can include ample
holes for a bone slurry (and/or new bone growth) to flow between
inter-vertebral space 55 and the inside of spacer 20. In a
preferred embodiment of the invention, spacer 20 is coated with a
bone-growth enhancing material, such as a hormone. Alternatively or
additionally, spacer 20 is coated with a material to which new bone
growth adheres. Alternatively or additionally, spacer 20 has a
rough finish, at least on portions thereof, to encourage bone
adhesion thereto. In one example, the finish is created by
sandblasting at least portions of the spacer. Alternatively or
additionally, the spacer may have holes and/or small protrusions
formed thereon, to encourage bone ingrowth. Such holes may be
formed on the tube portion and/or on the spikes. Preferably, areas
surrounding such holes are treated to be stronger, so that the
existence of the holes does not adversely affect the expansion
geometry of the spacer.
[0181] Alternatively, at least some parts of spacer 20 may be
treated to retard bone growth, for example by making them
radioactive or by coating them with bone-growth retarding material.
Such retardation may be useful in order to allow removal of the
spacer (described below). Preferably such retardation is
short-term, and the effect fades after a time, so that if the
spacer is not removed, bone growth will surround it. Alternatively
or additionally, at least a part of the spacer has a finish and or
a geometry (e.g., no holes) which discourages bone ingrowth.
Additionally or alternatively, the spacer may enclose or be
enclosed in an impenetrable material, for example a balloon, which
is inflated by the spacer being expanded. Possibly, the balloon
surface is conducive to tissue attachment and/or degrades after a
time. Alternatively, the balloon is attached to the spacer along
its length and the spacer is expanded by inflating the balloon.
[0182] Alternatively, such an outer mesh, fabric or balloon may be
used to enhance the contact between the spacer and the bone, for
example to increase the contact area and/or to prevent high
pressure contact points between the spacer and the surrounding
bone, except possibly at some desired locations. The mesh and/or
balloon are preferably inserted prior to the spacer and the spacer
is expanded inside the mesh or balloon. Alternatively, the mesh or
balloon is mounted on the spacer prior to the spacer being inserted
into the body. Possibly, the mesh is bioabsorbable, so that after
the bone grows in the mesh disappears. Alternatively to a mesh, a
more tightly woven fabric or a felt may be used. It is noted that
many temporary bone ingrowth structures, are known in the art and
may be provided between (and/or inside) the spacer and the
bone.
[0183] Flexible Filler
[0184] In an exemplary embodiment of the invention, spacer 20 is
used to provide a flexible joint between vertebrae 50 and 52. In an
exemplary embodiment of the invention, such a joint is achieved by
not injecting bone fragments. Possibly, the tips of the spikes of
spacer 20 are made wider, or include a widened section (described
below), to prevent undue embedding of the spacer into the
vertebrae. Alternatively or additionally, the cartilage is not
cleaned out of space 55 and/or new cartilage and/or cartilage
growth promotion materials are injected.
[0185] Alternatively or additionally, an elastic material is
provided about the spacer, for example, by injecting a precursor
and curing it or allowing it to cure in inter-vertebral space 55.
The spacer may be provided and/or expanded before, during or after
such curing. Alternatively, the elastic material is provided after
the spacer is expanded. In an exemplary embodiment of the
invention, the elastic material is one or a mixture of: PMMA
(polymethil methacrylate), polyethylene, polypropylene,
polyurethane, silicon, PTFE. Optionally, the material is mixed with
collagen, possibly collagen removed from intra-vertebral space 55.
Possibly, both slurry and flexible material are provided, for
example as a sandwich, with the bone slurry near the vertebra and
the elastic material in the middle. different parts of spacer 20
may be finished differently or coated with different materials, to
support the different types of surrounding filler.
[0186] In an exemplary embodiment of the invention, the spacer and
suitable amounts of the mixture or its precursors are provided
together as a kit.
[0187] In an exemplary embodiment of the invention, the mixture is
injected into the body and allowed to cure. Optionally, a curing
element, for example ultrasonic heater or ultraviolet light and/or
a chemical agent are provided into the body to assist the curing
process.
[0188] In an exemplary embodiment of the invention, spikes 24 serve
to anchor the elastic material to prevent it from migrating and/or
falling apart. Alternatively or additionally, threads may eb
provided with the mixture, so that the set mixture is a composite
material. Alternatively or additionally, spikes 24 couple the
elastic material to vertebra 50 and 52. Alternatively or
additionally, the formulation of the mixture and/or a coating on
the vertebra faces assist in the coupling to the vertebra.
[0189] In an exemplary embodiment of the invention, the flexibility
of spacer 20, for example, due to the length of the spikes is
utilized in providing a total flexibility for the joint. Possibly,
the spikes are made more flexible at their base, a thinner metal
and/or a different metal and/or metal processing method are used to
provide the desired flexibility.
[0190] Optionally, spacer 20 is enclosed in a balloon. Such a
balloon can enclose elastic material, a gel, saline solution and/or
small elastic particles, and prevent their migration. The balloon
may be pressed against the vertebra by spacer 20. Alternatively,
spikes 24 may transfix the balloon. Such transfixing may be
pre-manufactured (e.g., spacer and balloon provided as a single
combination) or be a result of the expansion of spacer 20.
Alternatively, the balloon is enclosed by spacer 20. Optionally,
the balloon is provided as a sleeve, possibly with flexible
materials, into which spacer 20 is inserted and expanded.
[0191] Capping the Spacer
[0192] The next step in the implantation method is preferably to
close up the incision used to provide spacer 20, or, more
typically, in a minimally-invasive procedure, to retract member 60.
In some preferred embodiments of the invention, the bone slurry may
be injected with a needle after member 60 is removed, rather than
while member 60 is still inserted.
[0193] In a preferred embodiment of the invention, spacer 20 is
attached to member 60, for example by a threaded coupler, so at the
end of the procedure member 20 is disengaged from spacer 60.
[0194] Alternatively, spacer 20 forms an extension of member 60. In
a preferred embodiment of the invention, spacer 20 is cut off at or
near the point where it enters inter-vertebral space 55, for
example using a cutting tool which is inserted inside or over
member 60. Alternatively, member 60 is twisted off spacer 20.
Preferably, a member 60 is weakened at its connection with spacer
20. It is noted that the un-expanded spacer portions are relatively
weak compared to the expanded portions (which may be firmly engaged
by bone). Thus, an un-expanded portion of spacer 20 may serve as
the weakened connection point. Possibly, member 60 is twisted off
spacer 20 (and then any resulting sharp edges may be smoothed off,
possibly using a tool inserted through or over member 60).
Alternatively or additionally, spacer 20 includes a sleeve which
overlaps the weakened connection point. Thus, when member 60 is
twisted off, any jagged edges remain covered by the sleeve and do
not come into contact with the tissue surrounding the spacer.
Alternatively or additionally, after the expansion of the spacer is
completed, the jagged end is capped. The cap may be threaded on the
end of the spacer. Alternatively or additionally, the cap has the
form of a bolt having an end-cap attached to an elongate threaded
portion. The elongated threaded portion engages the spacer,
possibly at its far end and the end-cap pushes against or engages
(possibly using a thread) the near end of the spacer. Other capping
mechanism are described below.
[0195] Alternatively or additionally, once the spacer is expanded
as shown in FIG. 2D, any extraneous spacer portion (i.e.,
protruding out of inter-vertebral space 55) is cut off. The removed
spacer portion may be expanded, partially expanded or non-expanded.
In a preferred embodiment of the invention, the cut is made from
inside member 20, for example using a rotating cutting edge which
is mounted on a narrow elongate member which is inserted inside
member 60.
[0196] Spacer Size Matching
[0197] One consideration in spacer implantation is ensuring spacer
20 fits inter-vertebral space 55. In a preferred embodiment of the
invention, a plurality of spacers are available for implantation
(for example in a kit), each with a different (compressed) axial
length and/or different radial diameter. The require spacer size
may be determined from measurements on a CT image or an x-ray image
of inter-vertebral space 55. Alternatively, an expandable element
may be inserted into the inter-vertebral space and, by the degree
of expansion of the element, the size of the space to be filled,
and the required spacer geometry, estimated.
[0198] Spacer Delivery Direction
[0199] In a preferred embodiment of the invention, the surgical
approach is from the back of the patient. Alternatively, a lateral
or a posto-lateral approach may be used. It is noted that the
implanted spacer may be very narrow during implantation, so it is
easier to plan an approach and/or use an approach direction that
cannot be provided using other fusion devices. Alternatively or
additionally, it is noted that the spacer, in some preferred
embodiments of the invention, may be made flexible along its main
axis, at least in its un-expanded configuration and especially as a
result of the slits formed therein. Thus, the spacer can be
provided at inter-vertebral space 55 using a curved guide, possibly
a bendable guide, such as an endoscope or a catheter.
Alternatively, if the spacer is formed of a shape-memory material,
the spacer may be cooled below the temperature at which it turns
ductile, so that it can be easily bent. Alternatively or
additionally, and especially if the spacer is elastic or
super-elastic, the spacer is maintained in a curved configuration
during insertion using a curved stylet inserted through the spacer,
alternatively or additionally to using a curved outer tube. FIG.
2P, below, describes an alternative method of insertion, which
utilizes the small-cross-section of the spacer and the flexibility
inherent in some expandable constructions, to allow an approach to
the vertebrate for a convenient direction.
[0200] In a preferred embodiment of the invention, the patient's
body is less traumatized, as the spacer is narrow. Alternatively or
additionally, the trauma of a prior art anterior is avoided by the
use of a narrow spacer or by using a different surgical approach.
It should be noted, that there is a wide rang of approaches that
can be used and even an open surgical incision may be used, still
reaping the benefits of not being required (or a lesser
requirement) to sacrifice facet joints, muscles, ligament, blood
vessels, spinal processes and/or other body structures.
[0201] Controlling Spacer Expansion
[0202] FIGS. 2E-2G illustrate various methods of effecting and/or
controlling the expansion of a spacer, in accordance with preferred
embodiments of the invention. In FIG. 2E, as shown the expansion is
essentially uncontrolled. A spacer 70 is expanded using an
expansion member 72 attached to its end-cap 74. When member 72 is
moved in the direction of the arrow relative to spacer 70, the
resulting stress axially collapses spacer 70, causing the spikes to
expand out. The order of expansion of the spikes is dependent,
inter alia, on the relative stiffness of the spikes. Usually all
the spikes will be about the same stiffness, so the expansion may
be gradual over the whole spacer or sudden at points which buckle
first. Alternatively, the spacer may be constructed so that some
spikes are weaker, by design, than other spikes, so that a certain
order of spike extension can be defined.
[0203] In a preferred embodiment of the invention, the relative
movement of member 72 comprises maintaining member 72 in location
relative to the vertebras and pushing spacer 70 towards the end of
member 72. Preferably, the relative motion is achieved by direct
application of force. Alternative, the relative motion is achieved
using a screw action, which can be more gradual and controllable.
Threading of the spacer may be anywhere along member 60. However,
in some preferred embodiments of the invention, spacer 70 is
provided with an inner thread at the end of the spacer opposite
from end-cap 74.
[0204] In a preferred embodiment of the invention, member 72 is
removed from spacer 70 at the end of the expansion process by
applying a sudden impulse force to break the connection between the
member and end-cap 74. Alternatively, member 72 is twisted off
end-cap 74. Alternatively, especially if the relative motion is
achieved using a threading of spacer 20, member 72 is coupled to
end-cap 74 using a thread which is preferably counter to the
threading of the spacer. Thus, member 72 can be screwed off. In
some embodiments the end-cap threading is in the same direction as
the threading of the spacer.
[0205] FIG. 2F illustrates a spacer 80 which is expanded using an
internal spacing member 82. However, unlike the example of FIG. 2E,
the expansion is controlled, using a collar 84 which does not allow
spikes to extend from spacer 80, except at designated areas.
Preferably, the designated areas are at the end of collar 84.
Alternatively, especially as shown with reference to FIG. 2G, the
designated areas may be distanced from the end of the collar.
Alternatively or additionally to an external collar 84, spacer 80
may also utilize an internal collar. Preferably, the internal
collar engages spacer 80 using an external thread on the collar
and/or an internal threading on spacer 80. Alternatively or
additionally, no threading is used. possibly, the spacer is
expanded by direct pulling and not by a screw-action.
[0206] In a preferred embodiment of the invention, movements of an
internal collar and an external collar are synchronized to a
control the expansion of the spacer. In one example, the spacer is
advanced out of the external collar by rotating the external collar
relative to the spacer (there is preferably a threaded coupling
between them). Thus, the newly "extruded" portion of the spacer is
unexpanded and unconstrained. Thereafter or possibly synchronously
therewith, the internal collar or a member 72 is retracted, again
possibly by rotating it relative to the spacer (preferably
utilizing a threaded coupling therebetween), causing axial strain
on the spacer, which expands the newly extruded portion. In some
embodiments, the internal and external collars may be rotated
simultaneously, but each of the collars has a different thread
angle relative to the spacer, so each translates a same rotational
movement into different axial movements.
[0207] In some embodiments, member 72 and/or an internal collar are
maintained at a desired angle relative to the spacer using a groove
in the member which matches one or more rails and/or a series of
protrusions on the inside of the spacer. In some embodiments, the
rail, groove and/or protrusions are not arranged in a straight
line.
[0208] Skipping ahead, FIGS. 2K and 2L illustrate shaped tips for a
collar 84, in accordance with a preferred embodiment of the
invention. One effect of the shaping is a preferential expansion of
one or more spikes (which are unconstrained by the collar) relative
to other spikes which are constrained, thereby allowing control of
the expansion of the spacer and/or extension of the spikes.
[0209] Returning back, FIG. 2G illustrates a spacer 90 whose
expansion is controlled using an external framework 92. In a
preferred embodiment of the invention, framework 92 includes a
plurality of holes 94. When spacer 90 is moved relative to
framework 92, spikes can only extend through pre-designated holes
94. The relative motion of the spacer may be achieved using any of
the techniques described above. It is noted however that since
spacer 90 is pushed against framework 92, there is no requirement
for an internal member, in some preferred embodiments of the
invention. In some preferred embodiments of the invention framework
92 is left in the body. In a preferred embodiment of the invention,
at least some of holes 94, have the form of axial or transverse
slots, through which spikes may extend. Thus, in some embodiments,
framework 92 comprises tines connected to a collar, the tines
defining the above slots, which are open in the direction of the
spacer. Such a framework may be retracted after the spacer is
expanded.
[0210] In a preferred embodiment of the invention, such a framework
may be used to control the distortion of a solid member, for
example a wire, in which the "expansion" is achieved by a straight
element folding into a wavy ribbon shaped element (each spike being
a bend in the ribbon). Preferably, a plurality of weakened points,
strengthened points and/or areas of increased cross-section are
formed along the wire, to limit and/or otherwise control the extent
of the wire which is pushed out through holes in framework 92.
Thus, the expansion of the spacer, at least for a ribbon-type
spacer, can be made independent of the axial length of the
spacer.
[0211] Alternatively or additionally, the expansion of the spacer
may utilize a balloon (not shown) which is inserted in the lumen of
the spacer and, when expanded, radially extends the spikes.
Generally, the "ring" segments of the spacer are not affected by
the balloon. Possibly, the balloon includes a plurality of fingers,
that push out the spikes, but do not affect the "rings".
Alternatively or additionally, the ring segments may also be
deformed by the balloon. In one example, the ring segments
comprises a mesh material, which can expand, but not as much as the
spikes. In a preferred embodiment of the invention, the ring
segments plastically deform at a greater applied force level than
the spikes, so that the spikes extend out before the rings are
deformed.
[0212] Exemplary Spacer Expansion
[0213] FIGS. 13A-13C illustrate an exemplary method of spacer
expansion, in accordance with a preferred embodiment of the
invention. A spacer 1002 is provided as a tube having an inner bolt
1008, which bolt preferably prevents the advance of the end of
spacer 1002, past the bolt. An outer collar 1004 is provided for
shaping the expansion of the spacer. A laproscopy tube 1006 is also
shown. In this embodiment, both bolt 1008 and tube 1006 are fixed
to a base 1010 outside the body. This base may be, for example,
fixed to the patient and/or his bed or it may be prevented from
advancing towards the body.
[0214] FIG. 13A shows a starting position, with bolt 1008 and
spacer 1002 (in its unexpanded state) extending between two
vertebrae (not shown).
[0215] Both spacer 1002 and collar 1004 are advanced. However, as
the spacer is prevented from advancing by bolt 1008, it expands, at
the areas where expansion is not prevented by collar 1004, forming
one or more spikes 1012. This result is shown in FIG. 13B.
[0216] Collar 1004 is then retracted (FIG. 13C), so that both the
collar and the spacer can be advanced again.
[0217] Spacer Removal
[0218] In some cases, it may be necessary to adjust the length of
the spikes after the spacer is inserted, possibly even a few days
after the spacer insertion procedure is completed. Also, if the
spacer is incorrectly implanted, for example, as evidenced by x-ray
images, it may be necessary to remove the spacer. In accordance
with preferred embodiments of the invention, the spacer can be
adjusted and/or removed.
[0219] In a preferred embodiment of the invention, removing the
spacer comprises un-expanding the spacer so that it has a narrow
diameter and then removing the spacer. Typically, the process of
un-expanding the spacer extends the axial length of the spacer, so
that some of the spacer may be "self-removing". Preferably, an end
of the spacer is restricted in motion, so that it does not move,
while moving another end away from the restricted end.
Alternatively or additionally, the another end of the (axially
extending) spacer is guided so that it does not impact on sensitive
tissues.
[0220] The tension of a spacer may be varied by increasing (or
decreasing) the spike length, thereby pressing with a greater (or
lesser) force against surrounding bone tissue. Alternatively, the
tension may be increased by adding resilient material into the
spacer or the inter-vertebral space, preferably using a needle. In
one example, shown with reference to FIG. 4E, a second spacer (142)
is inserted into a first spacer (144). Decreasing the spike length
may increase the length of the spacer by an unacceptable amount.
Preferably, the extra length of the spacer is cut off and removed
from the body.
[0221] Control of Spacer Characteristics
[0222] In a preferred embodiment of the invention, one or more of
the following three characteristics of the spacer should be
independently controllable: spacer axial length, spike length and
spike tension. In some embodiments, these characteristics are
controlled by selecting, for insertion, a particular spacer from a
set of available spacers. In other embodiments, a spacer may be
adapted to have the desired characteristics, for example, length
can be controlled by not expanding the entire spacer, and cutting
off the un-expanded portion. Additionally, in some embodiments of
the invention, it is desirable to modify the characteristics of a
spacer after it is inserted. Thus, allowing a spacer to be
maintained at--or modified to--an optimal operating configuration
while inside the body.
[0223] In some cases, what is desired is a modification of the
spacer length, with any associated change in tension or spike
length being undesirable or ignored. As described above, the
tension in a spacer may be increased by inserting a second
spacer.
[0224] FIGS. 2H-2J illustrate various methods of modifying
geometrical and/or tensile characteristics of a spacer, after it is
expanded. A trivial type of modification is removing the spacer and
optionally inserting a new spacer or the same spacer after it is
modified. In a preferred embodiment of the invention, removing a
spacer includes collapsing the spacer and then removing the
resulting narrow-diameter tube.
[0225] FIG. 2H illustrates a spacer 100, which is further expanded
or collapsed using a maintaining member 106 and a grasping member
104. In essence, member 104 engages one end of spacer 100 and
member 106 engages a second end of spacer 100. When the two members
are moved relative to each other, the spacer is expanded or
un-expanded. In a preferred embodiment of the invention,
maintaining member 106 engages an end-cap 108. The engagement may
be simple contact, fitting member 106 into a depression in end-cap
108 or a threaded connection. Grasping member 104 preferably grasps
spacer 100 at its near end 102, preferably using an internal
threaded connection on end 102. Alternatively, an external
connection to end 102, possibly a threaded connection may be used.
In a preferred embodiment of the invention, when modifying spacer
100, member 106 is maintained in place, so that end-cap 108 does
not advance into the body.
[0226] FIG. 2I illustrates a spacer 110 which is un-expanded (or
completely collapsed) by the insertion of a screw or a bushing 112
into the spacer. Alternatively, the screw remains in the spacer
when the spacer is inserted. Screw 112 engages a threaded end 118
and an end-cap 116. When the screw is turned, the spacer is
un-expanded. In a preferred embodiment of the invention, the screw
is inserted using a syringe, possibly forming a needle of the
syringe. Alternatively, the screw is engaged at a head 114, using
an inserted screw-driver.
[0227] In a preferred embodiment of the invention, screw 112 is
inserted into the spacer using a needle. In a preferred embodiment
of the invention, the screw is screwed into the spacer.
Alternatively, the near spacer end-cap has the form of a keyhole
with a larger diameter portion through which the screw can be
inserted and a smaller diameter portion which the screw can engage.
Optionally, instead of the far end-cap engaging the screw, it only
acts as a stop against which the screw can push.
[0228] In a preferred embodiment of the invention, the inner lumen
of the spacer includes a threading and/or protrusions which the
screw can engage. Optionally, the protrusions are created by the
expansion of the spacer. Additionally or alternatively, the
protrusions form a guide which guide an inserted needle of screw
through the spacer to its far end-cap, resisting deviations which
would make the needle/screw exit the side of the spacer.
Preferably, this type of guidance is provided when the spacer has a
bent configuration inside the body.
[0229] In a preferred embodiment of the invention, the near end-cap
of the spacer includes a flared opening to ease the insertion of a
screw, needle or screw driver head into the spacer and/or to engage
the end cap. Additionally or alternatively, a guiding mechanism may
be provided, for example, a magnetization of the end cap and a
corresponding magnetic sensor on the inserted object or an
ultrasonic transducer. Additionally or alternatively, a wire guide
remains attached to the spacer after it is inserted and an
endoscope or other inserted object may be guided to the spacer by
following the wire. Optionally, the one end of the wire exits the
body. Additionally or alternatively, the wire's end is easily
identifiable, for example, by having a large radius ball attached
thereto.
[0230] FIG. 2J illustrates a spacer 120 having an integral
expansion control mechanism. An internally threaded tube 122 is
provided in conjunction with an externally threaded screw 124. When
an end-cap 126 of the screw is rotated, the screw moves relative to
the tube and the spacer expands or un-expands. Alternatively, the
tube may be rotated and the screw is fixed (i.e., the tube is
rotatable relative to the spacer and the screw is fixed to the
spacer, at least with respect to its rotation). A screwdriver 128,
or at least its tip is preferably inserted until the screw.
Alternatively, spacer 120 may include a ratchet mechanism, whereby
a member 124 may be pushed into a holder 122, but it cannot move
back out (or vice-versa). In this case, a grasper, such as grasping
member 104 (FIG. 2H) is preferably provided so that motion of
spacer 120 can be controlled.
[0231] In one preferred embodiment of the invention, the interior
of spacer 120 provides the function of tube 122 (or of a holder
122), preferably being pre-threaded. In some embodiments, tube 122
is open at both ends or has holes defined therein, to aid in
expelling any material which may have accumulated in its lumen.
Alternatively or additionally, the diameter of screw 122 is small
enough so that it does not fill the entire inner cross-section of
tube 122.
[0232] In a preferred embodiment of the invention, screw 124 is
inserted after the expansion of spacer 120 is completed, preferably
as part of the insertion procedure. Alternatively, screw 126 may be
inserted after the fact, for example when it is decided that
adjustment may be desirable. Alternatively, screw 124 may inserted
to complete the expansion of spacer 120, during its original
expansion.
[0233] In a preferred embodiment of the invention, the modification
of the expansion of spacer 120 may be controlled by inserting an
internal or external collar or a framework, as shown in FIGS.
2F-2G. Thus, it is possibly to modify the spike length for only
part of the spacer (for example the middle or the ends) and/or to
compensate for increased axial length of one part of the spacer by
extension of spikes at another part of the spacer. Alternatively or
additionally, the threads and/or "end-caps" described with
reference to FIGS. 2E-2J may be located in other parts of the
spacer than its ends.
[0234] In a preferred embodiment of the invention, the "minimum
diameter" lumen of the spacer does not change when the spacer is
expanded or collapsed. Alternatively, the lumen may decrease, for
example, if portions of the tubes fold into the lumen rather than
outside like spikes.
[0235] Spacer Deformation Process
[0236] In a preferred embodiment of the invention, the spacer is
expanded and collapsed using plastic deformation of the spacer
material, whereby the tube is plastically deformed to form the
expanded spacer. Alternatively, at least one of the expansion or
collapsing uses elastic, super elastic or shape-memory properties
of the material. In one example, the spacer is formed so that it is
partially expanded and then elastically deformed to be completely
collapsed prior to insertion. Thus, when the expansion starts, some
or all of the spikes protrude from the spacer and increased axial
force on the spacer will only urge the spikes further out and not
in. It is noted that some parts of the spacer may be designed to
fold in, these parts may be elastically deformed away from their
"interior position", prior to inserting the spacer. FIG. 6XI-6XL,
described below, illustrate weakening portions of the spacer to
control the shape of the extended spike.
[0237] Alternatively or additionally, the spacer utilizes
super-elastic properties of the material it is composed of. In one
example, the spacer expands by itself to the expanded
configuration, what is required is to limit that expansion until
such expansion is desired. Such limitation may be achieved by
maintaining an axial length of the spacer or by providing an
external restraining tube which maintains the spacer in a collapsed
configuration. Alternatively, the axial length may be maintained
using an internal screw which engages the spacer over substantially
its entire length. In one embodiment, as the spacer is advanced out
of the restraining tube (or the screw), the unrestrained portion of
the spacer expands and/or engages the surrounding bone tissue.
[0238] In another example, the spacer collapses by itself to the
collapsed configuration, unless otherwise restrained, for example
by a screw as described above and with reference to FIGS. 2I and
2J. Additionally or alternatively, the spacer is maintained in
shape using an interlock mechanism, preferably a ratchet-type
mechanism. For example, in the embodiment of FIG. 8A (described
below) two tabs may butt or overlap. If one tab includes a
protrusion and the other tab includes a recess, when the tabs
overlap, the protrusion engages the recess and a ratchet mechanism
is formed. Additionally or alternatively, a dedicated ratchet
mechanism may be formed by a barbed elongated internal member of
the spacer which is connected at one end to the spacer and which
engages a different part of the spacer using the barbed other
end.
[0239] Alternatively or additionally, the expansion and/or
collapsing may be partly super-elastic and partly plastic or
elastic.
[0240] In a preferred embodiment of the invention, the
super-elasticity is achieved by constructing the spacer of a
shape-memory material, such as NiTi. Preferably, the material's
state transition temperature is set to be about 30.degree. C., so
that the spacer does not naturally pass through a transition after
it is already implanted.
[0241] In some preferred embodiments of the invention, the spacer
is collapsed by cooling it. In one embodiment, the spacer is formed
of a shape-memory material which is cooled to make it pliable and
then the spacer is collapsed as described above. In another
embodiment, the spacer is formed of a super-elastic portion and a
shape memory portion, with the (stronger) shape memory portion
maintaining it in an expanded configuration and a super elastic
portion applying forces to return to a collapsed configuration.
Possibly, two types of shape memory material are provided, each
with a different transition temperature. In a preferred embodiment
of the invention, when the spacer is cooled, the shape-memory
portion applies a weaker force and the spacer collapses. Possibly,
only a ratchet mechanism portion is formed of a shape memory
material and a super elastic material, with the rest of the device
being formed of a super-elastic material.
[0242] In a preferred embodiment of the invention, the entire
spacer comprises a single type of material--plastically deformed,
elastically deformed, super elastic or shape memory. Alternatively,
the spacer comprises multiple layers of material, each with
different properties. Alternatively or additionally, different
parts of the spacer may have different mechanical properties and/or
be formed of different materials. In one example, the ring segments
are plastic and the spikes are elastic. In another example,
different spikes may have different elasticity properties. In
another example, one side of the spacer may have one property and
another side of the spacer may have a different property.
[0243] Spacer End Cap
[0244] In some preferred embodiments of the invention, the end-cap
protrudes from the spacer after it is expanded (as does end cap 108
in FIG. 2H). In some cases, the end cap may include a spike to
engage bone tissue. Alternatively, the end cap may be formed to be
within a plane defined by the end-most spikes. In one example, this
is achieved by pre-folding the end-cap into the spacer.
Alternatively, the end-cap may be folded into the spacer as part of
the expansion process, for example (with reference to FIG. 2E),
inverting end-cap 74 by pulling on member 72. Alternatively, the
end-cap may be manufactured to elastically fold into the spacer.
Alternatively, the deformation of the end spikes may fold the
end-cap into the spacer. Additionally or alternatively, the end-cap
may be retracted after the expansion of the spacer by pulling of a
screw which engages the end-cap. Skipping ahead, FIG. 2O
illustrates a spacer in which the end-cap is formed to be inside
the spacer, so that the expanding spikes reach all the way to the
end of the spacer.
[0245] End-Cap Locking
[0246] Referring to FIG. 2I, in some embodiments, bolt 112 is not
threaded onto spacer 110, however, once the spacer expansion is
completed, the bolt is preferably locked to spacer 110, for example
at its end cap 118, not necessarily using threading.
[0247] Although FIG. 13A shows that spacer 1002 and bolt 1008
extend all the way from inside the body to an external base 1010,
In a preferred embodiment of the invention, the bolt and the spacer
are considerably shorter. Instead, spacer 1002 is advanced using a
pusher and bolt 1008 is restrained from advancing using a pole
element.
[0248] Many mechanisms may be used for locking the spacer and its
bolt. In a preferred embodiment of the invention, however, the
locking mechanism includes one or more of the following
features:
[0249] (a) retracting a spacer holding mechanism causes a locking
of the spacer;
[0250] (b) advancing a spacer holding mechanism, especially by
threading, causes a locking of the spacer;
[0251] (c) the mechanism is primed for locking only when the spacer
expansion is complete; and/or
[0252] (d) the locking mechanism is plastic (i.e., by deformation)
or elastic (i.e., a restraint is released that allows the mechanism
to lock).
[0253] Although the following locking mechanisms are shown as being
independent, in some embodiments, features from one locking
mechanism may be combined with features from another locking
mechanism, for example, the mechanism may combine fins on a spacer
and fins on a bolt in a same spacer device.
[0254] Locking Fins Embodiment
[0255] FIGS. 14A and 14B illustrate a fin based locking mechanism
in which one or more locking fins spring out from the bolt to
engage the spacer, thereby preventing it from collapsing. In other
embodiments, for example as shown below, the bolts are plastically
deformed and/or at least some of them may be provided from the
spacer, to engage the bolt.
[0256] FIG. 14A illustrates an expanded spacer 1020, schematically
shown, and having an inner bolt 1022.
[0257] A plurality of fins 1028 are shown extending from bolt 1022
and engaging an end-cap 1026 of spacer 1020. In this embodiment,
end-cap 1026 has inclined edges, for better engagement by fins
1028. Fins 1028 are preferably extended using a plastic,
super-elastic or shape-memory extension mechanism, however, other
mechanisms may be used instead. A pole element 1024 is shown
retracting from bolt 1022.
[0258] FIG. 14B shows spacer 1020 in an unexpanded state, in which
fins 1028 are restrained from expanding by spacer 1020 and also
prevent pole 1024 from retracting from bolt 1022, by engaging pole
1024 in depressions formed therein.
[0259] Referring back to FIG. 14A, pole element 1024 may be
advanced to ensure the complete extension of fins 1028 against
end-cap 1026. It is noted that the fins can so extend only if the
spacer is sufficiently axially contracted, since otherwise it is
within the cage. Furthermore, once the fins extend, pole element
1024 can be removed.
[0260] In some preferred embodiments of the invention, spacer 1020
is removed using a device that radially compresses the fins, so
that the bolt is unlocked from the spacer, thereby allowing it to
collapse.
[0261] In this and other embodiments, fins 1028 are preferably
proximal from the spacer portions where the spikes expand, to
prevent the fins from being engaged by the spikes. Alternatively or
additionally, the fins may be wider than the spikes. Alternatively
or additionally, the fins may be located at an angular offset from
the spikes, so they do not engage them. Alternatively, the fins may
be extended to engage the spacer at positions other than its end,
for example, by providing an end-cap having a plurality of axially
spaced fin-engaging locations along it or by allowing the fins to
engage an inner thread of the spacer or the spikes (from inside the
spacer).
[0262] Plastically Distorted Fins Embodiment
[0263] FIGS. 15A and 15B illustrate a locking mechanism similar to
that of FIGS. 14A-14B, except that it utilizes plastic deformation.
A plurality of fins 1038 are extended from a bolt 1032 to lock
against an end-cap 1036 by advancing a pole element 1034 towards
bolt 1032, thereby plastically deforming the fins to engage the
end-cap. Preferably, pole element 1034 is threaded to match a
threading in bolt 1032 and pole element 1034 is advanced by
rotation. The pole may be retracted by unscrewing it.
Alternatively, the threading may be extend along only a portion of
the circumference so that when a half turn is completed, pole
element 1034 is released from the threading.
[0264] Distorting Ring Embodiment
[0265] FIGS. 16A-16F illustrate a locking mechanism utilizing an
expanding flange, in accordance with a preferred embodiment of the
invention.
[0266] FIG. 16A shows a spacer 1040, prior to it being locked to a
bolt 1042, by a flange 1048 of the bolt. A pole element 1044
preferably engages bolt 1042, for example by being threaded
thereto.
[0267] In FIG. 16B, pole 1044 is advanced relative to bolt 1042,
thereby expanding flange 1048 so that it is wider than an aperture
defined by an end-cap 1036, so the spacer cannot retract from the
bolt.
[0268] FIG. 16C is a blow-up view of a pushing tube 1049, showing a
projection 1047 formed at the end of the tube, for engaging a
matching notch in spacer 1040. The matching projection and notch
allow maintaining and controlling the angular orientation of spacer
1040, inside the body, using pushing tube 1049.
[0269] FIG. 16D is a diagram showing details of the construction of
pole element 1044.
[0270] FIG. 16E is a perspective view of bolt 1042, showing a wide
base 1043, which prevents the advance of spacer 1040 past the bolt,
when the spacer is advanced as shown in FIGS. 13A-13C.
[0271] FIG. 16F is a diagram showing details of the construction of
bolt 1042.
[0272] Fins On Spacer Embodiment
[0273] FIGS. 17A-17C illustrate an alternative locking mechanism in
which fins on a spacer engage a bolt inside of the spacer. FIG. 17A
shows the configuration prior to activation of the locking
mechanism. A spacer 1050 has a plurality of fins 1058 formed at its
end. A bolt 1052, inside the spacer, comprises one or more
depressions 1057, which may be formed as a band around bolt 1052. A
pushing tube 1059 includes inwardly protruding tips 1056, which
engage fins 1058 when the fins are not in depressions 1057. Thus,
pusher tube 1059 does not slip off spacer 1050.
[0274] When the spacer is contracted sufficiently, fins 1058 will
match up to depressions 1057. By retracting pusher 1059,
protrusions 1056 will urge fins 1058 into depression 1057, locking
bolt 1052 against spacer 1050. Preferably, this motion of fins 1058
will also simultaneously free, pusher 1059 to be retracted,
however, this is not essential. In a preferred embodiment of the
invention, a sleeve 1055, possible the laproscopic tube 1006 is
provided to insure that fins 1058 bend in, rather than protrusions
1056 bending out. Optionally, a plurality of axially spaced
depressions 1057 is provided, to allow for various expansion
geometries of spacer 1050,
[0275] FIG. 17B shows the configuration after the activation of the
locking mechanism.
[0276] FIG. 17C is a perspective view of the configuration of FIG.
17A, without the sleeve.
[0277] Pull-out Locking Mechanism
[0278] FIGS. 18A-18D illustrate a locking mechanism in which fins
on a bolt are extended when a pole element of the bolt is
retracted, in accordance with a preferred embodiment of the
invention.
[0279] FIG. 18A shows a spacer 1060 in an unexpanded configuration.
An extension 1065, of a pole element 1064, is held by a plurality
of inwardly bent fins 1068 of a bolt 1062. Extension 1065 contacts
and is axially constrained by a surface 1063 of the fins. Fins 168
are maintained in an inwards configuration by spacer 1060.
[0280] In FIG. 18B, the spacer is sufficiently axially contracted,
that fins 1068 can extend over an end-cap 1066 of spacer 1060. This
extension may be elastic, super-elastic or shape-memory based.
Alternatively, when pole 1064 is retracted relative to a pusher
1069, extension 1065 is urged against surface 1063 of fins 1068,
causing fins 1068 to extend out and engage end-cap 1066.
[0281] Alternatively to the fin design shown in which surface 1063
is far from the tip of the fins, surface 1063 may be closer to the
tips of the fin, thus requiring less force to extend the fins, if
the base of the fin (generally the part that bends) is not also
advanced towards the tips of the fins. This may result in a longer
extension 1065 than shown.
[0282] FIG. 18C is a perspective view of bolt 1062, showing also
its base 1061.
[0283] FIG. 18D is a perspective view of pole element 1064, showing
a preferred attachment method between extension 1065 and the rest
of pole 1064.
[0284] Ring Locking Embodiment
[0285] FIGS. 19A-19C illustrate a ring-based locking mechanism, in
accordance with a preferred embodiment of the invention. A cage
1070 and a bolt 1072 are locked together using a ring 1075, that
matches a groove 1077 formed in bolt 1072, thereby locking the bolt
against an end-cap 1076 of spacer 1070.
[0286] In FIG. 19A, the spacer is unexpanded. As a pusher 1079 is
advanced, spacer 1070 axially contracts and radially expands.
Concurrently ring 1075 is advanced towards spacer 1070.
[0287] In FIG. 19B, ring 1075 contracts into groove 1077, thereby
locking the spacer.
[0288] FIG. 19C illustrates an exemplary ring 1075, which is
preferably formed of a super-elastic material, such as Nitinol,
however, this is not required.
[0289] Tube Cross-section
[0290] In a preferred embodiment of the invention, the
cross-section of tube 22 (FIGS. 1A-1D) is circular. Alternatively,
other cross-section are used, for example, polygon cross-sections,
such as a triangle or a square. Preferably, the spikes are formed
on sides of the polygon. Alternatively or additionally, they are
formed at vertexes of the polygon. In a preferred embodiment of the
invention, the inner cross-section of the tube and the
outer-cross-section of the tube have the same geometry and/or are
aligned. Alternatively, the tube 22 comprises a radially uneven
thickness of material. In one example, the inner cross-section is
triangular and the outer cross-section is a square or a circle.
Alternatively or additionally, the cross-sections may be asymmetric
relative to the main axis of tube 22. Alternatively or
additionally, the cross-section geometry of the tube may change
along the axial dimension of the spacer. In a preferred embodiment
of the invention, variations in the cross-section and/or tube
material thickness are related to the spike positions and/or
desired function. In one example, the tube diameter increases at
the end-caps.
[0291] Wires
[0292] FIG. 2M illustrates a wire 121, which can be used, for
example, to restrict the expansion of the spacer. In the figure,
wire 121 will restrict the allowed distance between the peaks of
its adjacent spikes, spike 123 and spike 125. If such wires are
formed between the peaks of all the spikes in the circumference of
the spacer, the maximum extension of the spike swill be limited by
the length of the wires. Alternatively or alternatively, the wire
may only limit the angular distance between two spikes.
Additionally or alternatively, such a wire may connect between a
spike and a non-extending portion of the spacer. Additionally or
alternatively, such a wire may be attached to a part of a spike
other than its peak, for example to the middle of a spike's leg. As
can be appreciated, in some preferred embodiments of the invention,
the wires are not uniformly distributed over the spacer, for
example being a function of axial position, radial position and/or
spike geometry or distribution. Alternatively or additionally, some
wires may be cut or removed by a physician prior to insertion of
the spacer.
[0293] Spacer Cross-section
[0294] Typically, the cross-section of an expanded spacer is
preferably selected to match a desired usage. In the vertebra, a
disc may be replaced with two parallel spacers, one on each side of
the spine. In this configuration, the cross-section of the
inter-vertebral spacer approximates a rectangular box, which is
thicker in the middle than at its ends. In a preferred embodiment
of the invention, the axial variation in cross-section may be
provided by varying spike length or tube diameter, as described
above. Alternatively or additionally, the cross-section shape of
the spacer may be varied from being a circle, for example to be a
rectangle or a square. It is also noted that a square spacer often
moves around less than a circular spacer does.
[0295] In a preferred embodiment of the invention, the geometry of
the cross-section may vary along the axis, for example the radius
increasing or decreasing with axis or approximating an hour-glass
shape or a cigar shape. Alternatively, the cross-sectional shape
may vary, for example from being a circle at on end of the spacer
to being a square at the other end of the spacer.
[0296] Spacer Axis Geometry
[0297] In a preferred embodiment of the invention, the axis of tube
22 in its collapsed and expanded configuration is substantially
straight. Alternatively, the axis of the spacer may be curved or
broken piece-wise while the spacer is inserted and/or after
insertion is complete. Alternatively or additionally, the axis of
the spacer may be curved or broken in the collapsed spacer.
[0298] In one example, the spacer is manufactured in a bent
configuration to aid its insertion. During insertion the spacer is
preferably straitened and/or otherwise adapted to the space into
which it is inserted.
[0299] In another example, the spacer is inserted straight and then
bent to adapt the spacer to the insertion space. In one example, a
"C" shaped or horse-shoe shaped spacer replaces an entire disc with
a single spacer.
[0300] The spacer may be pre-formed to be axially bent and then
elastically or super-elastically maintained in a different
configuration for insertion. Alternatively, the spacer is
plastically deformed during the expansion, for example (with
reference to FIG. 2E) if member 72 is a curved stylet or (with
reference to FIG. 2F) using a curved collar. Alternatively, the
spacer is bent after it is partially or completely expanded, for
example by inserting a bendable stylet into the lumen of the spacer
and then bending the stylet (from outside the body).
[0301] Alternatively or additionally, the spacer may be designed so
that it bends when it is expanded. In one example, the spike slots
are made uneven on opposing sides, so that the ring segments have a
different axial dimension on opposite sides of the spacer. FIG. 2N
is a layout of a spacer in which one spike "A" is shorter than a
second spike "B" on the opposite side of the spacer. When the
spacer is expanded, the uneven spike lengths will cause the spacer
to bend.
[0302] In another example, the spike lengths are unequal on the two
sides of the spacer, so when they push against the surrounding
bone, the inner lumen is bent. Alternatively, the bending
configuration is selected to create a desired contact and/or
contact pressure between the spikes and the surrounding bone.
Additionally or alternatively, the spike lengths and/or the slots
are designed so that the spacer twists around its axis as it is
expanded, for example, as shown in FIG. 5, where the spike slots
are not parallel to the spacer axis.
[0303] Space Filling Spacer
[0304] In some embodiments, it is desirable that the spacer fill
the intra-vertebral space as completely as possible. In particular,
it is desirable to maximize the contact area between the spacer and
the vertebrae. As a result, it is expected that the spacer will
embed less into the vertebra. As described below, this result may
be achieved by surrounding the spacer with a mesh, fabric or a
balloon. Alternatively, spike shapes, such as described below with
reference to FIGS. 6F and 6C also increase the contact area. In the
example of FIG. 6F, a small extension of the spike is provided to
enter into the vertebra, to prevent slippage of the spacer.
[0305] FIG. 2P illustrates a spacer 130 having an inner axis 136
which is not parallel to an axis of the expanded spacer. In a
preferred embodiment of the invention, spacer 130 is inserted into
an intra-vertebral space 55 at an angle which is oblique relative
to the main axes of the space, minimizing, the danger of damage to
important body structures. However, when the spacer is expanded, an
asymmetrical arrangement of spike lengths causes the final profile
of the expanded spacer to match intra-vertebral space 55. In the
example of FIG. 2P, spikes 132 decrease in length along the spacer
and corresponding spikes 134 on the opposite side of the spacer
increase in length. Optionally, a second spacer may be inserted,
from the other side of the intra-vertebral space, along a doted
line 138, indicated in the figure. In the embodiment of FIG. 2P the
lengths of the spikes which are perpendicular to the plane of the
figure are preferably equal. However, in other embodiments these
spikes may also exhibit uneven lengths. In a preferred embodiment
of the invention, elongate member 60 (FIG. 2) has a marking or a
groove thereon which indicates the correct orientation of the
spacer.
[0306] Struts
[0307] In a preferred embodiment of the invention, when the spacer
expands and spikes extends, additional structural elements, called
herein "struts", extend between two (or more) spikes or between one
(or more) spike and the tubular portion of the spacer. For clarity,
various struts configurations (in expanded spacers) will be
described and then mechanisms for generating such strut
configurations will be described.
[0308] FIGS. 3A-3E are axial views of spacers with struts in
accordance with preferred embodiments of the invention. Referring
to FIG. 3A, a spacer 200 (when expanded) comprises a tubular
portion 206 and a plurality of spikes 202 extending radially
therefrom. A plurality of struts 204 connect peaks of spikes 202.
In the example of FIG. 3A, the profile of the expanded spacer is
rectangular, and four struts are provided, to form a rectangular
profile which bounds the spikes.
[0309] A larger or smaller number of spikes may be defined for the
circumference, for example, as shown in FIG. 3B, six spikes and six
struts are provided.
[0310] Not all the spikes need to be completely inter-connected by
struts, for example as shown in FIG. 3C, a strut 204A connects a
spike 202A and a spike 202B; a strut 204B connects a spike 202C and
a spike 202D; while no strut connects spikes 202A and 202C or
spikes 202B and 202D.
[0311] Additionally, the pattern of interconnection of struts need
not be symmetric. For example as shown in FIG. 3D, spikes (and
struts) extend only to one side of the spacer. Possibly, these
and/or other various in the struts are a function of the axial
and/or radial position along the spacer.
[0312] Additionally, some spikes may be connected to struts and
some not connected to any struts at all. For example as shown in
FIG. 3E, where two spikes 210 and 212 are connected by a strut 214,
while two spikes 216 and 218 are not connected to any spikes.
[0313] In FIGS. 3A-3E, the struts are shown connected spikes which
are at a same cross-section of the spacer. In some of the examples
a complete ring (actually a polygon) is defined by the struts.
Alternatively, the struts may connect spikes which are (also)
axially displaced. Thus, possibly, a strut may be substantially
parallel to the axis of the spacer. In an example of a strut
interconnection pattern, the strut interconnection pattern may
define a spiral around the spacer axis. These axial
interconnections may be additional to or alternative to connection
around the circumference of the spacer.
[0314] In the above Figs., struts were shown as connecting peaks of
adjacent spikes. In a preferred embodiment of the invention, struts
connect non-adjacent spikes. Alternatively or additionally, struts
are connected, at least at one side thereof, to a non-peak portion
of a spike, possibly even to a non-spike portion of the spacer, for
example the tube, a wire or another strut.
[0315] In a preferred embodiment of the invention, struts are
straight. Alternatively, at least one of the struts is bent. In one
embodiment, the strut is pre-bent. In another, the strut is bent by
the expansion process, for example by a wire or a second strut
connected to the center of the strut. Preferably, weakened points
are defined on the strut, to guide its bending.
[0316] FIGS. 3F-3M illustrate one mechanism of providing struts
between spikes, in this example struts which ring the spacer at the
spike peaks. In other embodiments of the invention. struts may be
provided using additional or alternative different mechanisms, for
example by forming the spacer from a layered material in which the
struts are defined by a layer other than that which defines the
spikes.
[0317] Spacer Joints
[0318] In this context it is useful to consider several types of
joints and relative movements of joints movements:
[0319] (a) joints which experience only axial translation during
the expansion process, for example base joints of a spike;
[0320] (b) joints which experience radial translation during the
expansion process, for example peaks of spikes; and
[0321] (c) joints which experience angular motion.
[0322] In addition, several types of relative motion may be
experienced between pairs of joints, for example:
[0323] (a) no relative motion--two spike base joints at the same
circumference of the spacer;
[0324] (b) axial translation--two base joints of the same
spike;
[0325] (c) radial translation--a base joint and a peak joint of a
spike;
[0326] (d) constant distance--a base joint and a peak joint of a
spike;
[0327] (e) changing distance--two base joints of the same spike;
and
[0328] (f) angular translation--when the spacer twists while it
expands.
[0329] In some cases, these various types of motion and relative
motion may be combined in a single joint.
[0330] Strut Geometries
[0331] FIGS. 3F and 3G illustrate a spread view (3F) and an axial
view (3G) of a spacer with struts in a collapsed condition. In a
spread view, the spacer is axially split, spread open and viewed
from above (somewhat like a cylindrical map projection).
[0332] FIGS. 3H-3J illustrate the same spacer in a semi-expanded
condition (spread, axial and side views), in which the spikes are
extended but the struts are not in their final position.
[0333] FIGS. 3K-3M illustrate the same spacer in a final expanded
condition (spread, axial and side views).
[0334] This set of figures is somewhat schematic and, in some
cases, the correct geometry is somewhat distorted or small features
shown in one figure are not shown in another, corresponding
figure.
[0335] In the following description, the motion of the spikes has
been separated from the motion of the struts, to simplify the
explanation. However, in some embodiments of the invention, what is
described herein as separate steps is actually a single combined
step in which spikes extend while the struts move to their final
positions. In addition, for simplification, spikes are shown as
having a zero width and a zero thickness, which is not the case in
an actual embodiment.
[0336] FIG. 3F is a spread layout of an axial portion of a spacer
showing four spikes: AEI, BFJ, CGK and DHL. "AEI" describes a spike
in which the two base joints are "A" and "I" and the peak joint is
"E". struts are defined between the peak joints as follows: EF, FG,
GH and HE. Point "E" which appears in both sides of the figure is
the same point, duplicated by the layout view.
[0337] FIG. 3G is an axial view of the collapsed spacer, in which
points A,E,I (and D,H,L, C,G,K, B,F,J) are shown as a single
point.
[0338] FIG. 3H is a spread layout of the spacer after the spikes
have been completely extended. Each spike AEI, BFJ, CGK and DHL is
shown substantially as a single point. It is noted that the spikes
are still axially displaced.
[0339] FIG. 3I is an axial view of the spacer, in which the spikes
are seen to be extend and the struts interconnect the peaks of the
spikes.
[0340] FIG. 3J is a side view of the spacer, showing that the
struts are in a non-final configuration. It is noted that the
extension of the spikes causes the struts to be lifted from the
surface of the spacer, so that they are spaced apart from the
spacer. The spikes, however, are attached directly to the spacer,
at least at one of their ends.
[0341] FIG. 3K is a spread layout of the spacer after the expansion
(and axial contraction) is completed. The spikes are shown as all
being at substantially a same axial position of the spacer.
[0342] FIG. 3L is an axial view of the spacer, showing the spikes
and the struts being fully deployed.
[0343] FIG. 3M is a side view of the spacer showing that the spikes
and the struts are at a same axial position.
[0344] Spacer Parameter Control
[0345] In the design of a spacer, the properties of the collapsed
and/or expanded spacers may be modified by controlling various
aspects of the spacer. In particular, one or more of the following
aspects may be modified:
[0346] (a) length of collapsed spacer;
[0347] (b) geometry of collapsed spacer;
[0348] (c) length, width, number, density and/or geometry of
spikes;
[0349] (d) relative positioning of spikes among themselves and/or
the rest of the spacer;
[0350] (e) elasticity, stiffness, plasticity and other mechanical
properties of the material(s) which compose the spacer and/or of
the spikes and/or of non-expanding portions of the spacer (if
any);
[0351] (f) metallurgic and other treatments of the spacer;
[0352] (g) thickness and variations in thickness of the spacer
material; and
[0353] (h) coating.
[0354] In particular, especially as described herein, the above
aspects may be different for different parts of the spacer and/or
for different spikes. Alternatively or additionally, these aspects
may vary temporally, for example, elasticity varying as a result of
gradual "learning" of the spacer.
[0355] Spacer Manufacture
[0356] In a preferred embodiment of the invention, the spacer is
manufactured by laser cutting or e-beam cutting a metal tube. The
metal tube may be formed as a tube, for example by extrusion or it
may be formed into a tube from a sheet, for example by welding.
Preferably, such a weld line, which may not be straight, lies
between spikes. Possibly, the sheet is first cut and/or otherwise
at least partially shaped and then formed into a tube.
[0357] In some preferred embodiments of the invention, selected
portions of the spacer are metallurgically treated. In one
embodiment, a portion of the spacer is annealed by heating (not
cutting) that portion, for example, with a laser, an e-beam or a
plasma beam. Alternatively or additionally, the rest of the spacer
is protected from the heating of the beam, for example using an
external or internal heat dissipating mold or by using a mask,
which block heat-causing beams. Possibly, the mold comprises a heat
conducting material, such as copper or aluminum. Alternatively or
additionally, the mold includes active cooling, for example water,
oil or gas cooling or cooling by sublimation of the mold
material.
[0358] In a preferred embodiment of the invention, the annealing is
used to make points or areas that twist or bend more malleable,
while maintaining non-distorting portions (such as spike legs and
struts) more rigid.
[0359] Other possible types of local metallurgic treatments
(possibly utilizing a mold) include, localized ablation (not
cutting through), deposition of ions, local sintering, local
welding, cladding, plating, drilling of small holes and/or
attaching additional thickness of material. It should be noted that
in some embodiments, even the entire spacer can be annealed, as the
many parts of the spacer are cold-worked by the expansion process.
Optionally, the expansion process takes care not to overly distort
areas on the boundary between annealed and un-annealed portions,
for example by providing a suitable mold for the expansion to occur
against, for example the collars of FIG. 2.
[0360] In a preferred embodiment of the invention, the annealing
processes utilize a sensor (contact or non-contact) to provide
feedback on the local temperature achieved at the annealed location
and/or locations not to be annealed. For example, the sensor may be
used to prevent the metal from being melted by the annealing beam.
The sensor can be used for real-time control of the beam intensity
and dwell time. Alternatively or additionally, the sensor is used
to determine if a certain location needs additional treatment to
achieve annealing.
[0361] FIG. 20 illustrates a portion 1100 of a spacer, on which
figure banded areas illustrate portions to be annealed, to assist
in the expansion of the spacer, in accordance with a preferred
embodiment of the invention.
[0362] As shown in FIG. 20, the slits that define the spikes do not
have to be straight and can be curved, for example. As shown, the
spike shape is that of an hour-glass. It is noted that by annealing
the center of the spike, also inverse hourglass shapes can be
provided.
[0363] The hole sin the spacer, used to relive stress, need not be
round, for example as shown in FIGS. 21A and 21B, the shape of the
slits and the holes is that of a spline. Such a shape may be
desirable as the spike extends out of the spacer plane, applied
non-planar stress to the spacer. The measurements shown are for a
lordotic spacer having a 11.times.11 mm cross-section and a 4 mm
tube cross-section
[0364] As described in a PCT application filed on even date in the
Israel receiving office, such local annealing may also be applied
to other implant types, such as dental implants or intramedullar
nails and especially to portions of such medical orthopedic
implants where significant elongation, such as 40% or more is
required.
[0365] In preferred embodiments of the invention, the spacer is
subjected to one or more of the above treatments and/or one or more
of the above aspects and/or design properties of the spacer are
modified, especially as described herein, in order to achieve one
or more of the following desired spacer properties:
[0366] (a) resilience profile of the spacer, preferably as a
function of direction of force application;
[0367] (b) collapse profile, i.e., how much radial force will cause
the spacer to (typically undesirably) collapse and how much will it
collapse;
[0368] (c) resistance to axial, rotational, radial, twisting and/or
flexing motion, prior, during and/or post insertion;
[0369] (d) amount of conformance to body-structure geometry and
ability to adapt, while being expanded and/or after being in place,
possibly requiring variations in properties over the spacer;
[0370] (e) type and/or extent of contact with bone, especially with
respect to digging into bone;
[0371] (f) surface area, especially with respect to adherence to
new bone growth and/or danger of irritating the body;
[0372] (g) ease and/or method of insertion, expansion, bone
anchoring, adjustment and/or retraction;
[0373] (h) size of playground, i.e., the allowed error in matching
a particular spacer to a particular medical situation; and
[0374] (i) support and/or enhancement of new bone growth.
[0375] Spacer Surface Treatment
[0376] In a preferred embodiment of the invention, the spacer is
made of unalloyed Titanium grade 2, as per ASTM F67. An inner bolt
is preferably made from Ti-6AL-4V, per ASTM 136.
[0377] In a preferred embodiment of the invention, the spacer is
(optionally) thermally treated at between 650-800.degree. C.,
preferably in a vacuum or a non-reacting atmosphere. Other
temperature ranges and/or various annealing times may be used, for
example above 400.degree. C., above 700.degree. C. or above
800.degree. C. Preferably, but not necessarily, the temperature is
lower than 1100.degree. C., 1000.degree. C. or 900.degree. C.
Exemplary annealing times are 1 millisecond, 1 second and 10
seconds. Typically, the annealing times and temperatures vary with
the material type and/or previous processing of the material. In
some cases, even surface melting is desirable.
[0378] The spacer is formed from a tube (by cutting) either before
or after the thermal treatment. However, the spacer may also be
formed from a sheet or using other methods.
[0379] Thereafter, several treatments may be applied to the spacer,
for example one or more of the following, in order to remove
contaminants, remove debris from the forming process, smooth sharp
edges, deburr and/or reduce micro-fractures.
[0380] In a first treatment, the spacer is soaked in a reagent
containing 5 ml of HNO.sub.3, 2 ml of HF and completed to 100 ml
using H.sub.2O, for 100 seconds at 25.degree. C. The spacer is then
washed and rinsed off in an ultrasound agitated water bath at
60.degree. C. the spacer is then air-dried.
[0381] In a second treatment, mechanical cleaning, the spacer is
placed in a trumal, sprayed with glass (preferably using small
crystals), sand-sprayed and/or polished with diamond paste
(preferably with a small grain size).
[0382] Alternatively or additionally, an electropolish method is
used, for example using a mixture of 660 ml methanol, 440 ml
2-butoxy-ethanol and 66 ml perchloric acid or a mixture of 70%
HNO.sub.3, 10% HF and 20% H.sub.2O (by volume). An exemplary
current is about 100 mA/mm.sup.2. An exemplary voltage is about
15V
[0383] Alternatively or additionally, a surface treatment
comprises:
[0384] (a) applying a light base after laser-cutting to remove fat
and debris;
[0385] (b) water washing;
[0386] (c) pickling at room temperature for between 1 and 5
minutes;
[0387] (d) water washing;
[0388] (e) washing in 60.degree. C. ultrasonically agitated water;
and
[0389] (f) air drying.
[0390] Exemplary acids for pickling are a mixture of HNO.sub.3
20-40 ml, HF 1-2 ml and completed to 100 ml using H.sub.2O or a
mixture of HNO.sub.3 10 ml, HF 5 ml and Lactic acid 30 ml.
[0391] Another exemplary surface treatment is a salt bath:
[0392] (a) soaking for 5-10 minutes in a 20.degree. C. salt
bath.
[0393] (b) water wash;
[0394] (c) between 2-5 minutes soaking in a 10% by volume solution
of H.sub.2SO.sub.4
[0395] (d) water wash; and
[0396] (e) repeating the acid soak until a desired layer thickness
is removed. By selectively coating the spacer with acid resistant
material, selective etching can be achieved.
[0397] Square Spacer Embodiment
[0398] FIG. 4A shows a flat projection of a spacer having a square
cross-section when expanded, in an un-expanded configuration, in
accordance with a preferred embodiment of the invention. FIG. 4B
shows a flat projection of the spacer of FIG. 4A, in an expanded
configuration. FIG. 4C shows a perspective projection of the spacer
of FIG. 4A, in an expanded configuration. The above figures also
include measurements for a preferred embodiment of the invention.
For example, a length of 114 mm (un-expanded) and 23.9 mm
(expanded), a diameter of 4 mm (un-expanded) and 14 mm
(expanded)--each side, the material may be titanium, with a
thickness or 0.5 mm. Alternatively or additionally, the material
may comprise Nitinol (NiTi), Titanium, Surgical Stainless Steel,
plastic, composite and/or various alloys, such as bio-inert metal
alloys.
[0399] In some embodiments of the invention, the spacer is made
bio-absorbable, so that as bone ingrowth proceeds the spacer
decomposes. Thus, the spacer is less likely to exert localized high
pressure on the vertebra (which may cause remodeling). Possibly,
only some of the spacer is absorbed, for example, sharp edges
thereof.
[0400] Spacer Finish
[0401] In a preferred embodiment of the invention, the spacer as
described herein or elsewhere in this application, has a smooth
surface. Smooth surfaces are generally less prone to fracture
and/or micro-fracture propagation. Alternatively or additionally,
at least some of the spacer surface is rough, to encourage bone
growth and/or adherence. Alternatively or additionally, at least
some of the spacer surface includes small barbs, to engage the bone
and or soft tissue. In some embodiments, only the tips of the
spikes and/or areas near the tips have non-smooth surfaces. Such
roughness and/or barbs may also be achieved by coating a smooth
spacer.
[0402] Lordotic Spacer
[0403] FIG. 4D illustrates a variation of the spacer of FIGS.
4A-4C, in which spikes only extend in six transaxial directions and
not eight, in accordance with a preferred embodiment of the
invention.
[0404] A spacer 1121 is shown in a side view 1120. Optionally, and
as shown, the cross-section diameter increases with the axis, with
a greater diameter preferably provided for the side near the
stomach of the patient.
[0405] A front view 1122 illustrates that only six spike directions
re utilized. Spikes 1126 server to separate the two vertebras and
spikes 1124 serve to stabilize spacer 1121. No Horizontal stress
exists in the back, so horizontal pointing spikes are not provided
in this embodiment.
[0406] Double Spacer
[0407] FIG. 4E illustrates a spacer configuration in which one
spacer 142 is expanded inside another spacer 140, for example, to
increase the total stiffness of the spacers. In a preferred
embodiment of the invention, spikes 146 of inner spacer 142 match
the hollows of spikes 144 of outer spacer 140. Alternatively or
additionally, spacer 140 may function as a mold for expansion of
inner spacer 142 (for example as in FIG. 2G). In some embodiments,
this may require the spikes to be sharper on the inner spacer
and/or the internal structure of the outer spacer to be more
guiding, such that the expanding inner-spacer spikes are suitably
guided.
[0408] Alternatively, spikes 146 may not match spikes 144, for
example as shown by dotted line 148. Preferably, the two spacers
are selected so that none of the spikes match or so that spikes
only on one side and/or one portion of the spacers match.
[0409] Generally, the inner spacer is inserted into the first
spacer if it is determined that the stiffness of the first spacer
is too small. In some cases this may be the result of the expansion
of spacer 140 being limited, so the base of spikes 144 is wide
(resulting in a weak spike). Preferably, the inner spacer is
inserted during the same procedure. Alternatively, an inner spacer
may be inserted later, possibly a few days after the first
procedure is completed.
[0410] Alternatively or additionally to inserting spacers one
inside the other, multiple spacers may be used for a single
inter-vertebral space (or other body space) in other
configurations. In one configuration, a disc is replaced by two
parallel spacers, on one each side of the spinal column. Generally,
the two spacers do not touch. Alternatively, the two spacers may be
bent and touch at one or two of their ends. In another example,
two, three, four or more spacers may be inserted to be coaxial, for
example in series and/or to be co-planar, for example side-by side.
Typically, the spikes on the two spacers interlock, at least as a
result of friction and/or inherent flexibility of the spikes. In
some cases, the spike spacing and/or spike shapes may be selected
to encourage or discourage such an interlock. When the spacers are
inserted in series, the spacers may include forward folding and/or
rear-folding spikes, to encourage interlocking. The multiple
spacers may be expanded in parallel. Alternatively, a second spacer
is expanded only after a first spacer is already expanded. Possibly
however, the expansion of the first spacer may be adjusted to match
the expansion of the second spacer. In some cases, the spacers are
not coaxial, for example their axes being somewhat perpendicular,
for example as described with reference to FIG. 2P.
[0411] Alternatively or additionally, multiple spacers may be used
to fill a space where, possibly, a single straight spacer would
have sufficed. However, in some cases better control over the
spacing and/or spinal support are achieved using multiple
spacers.
[0412] In one preferred embodiment of the invention, the spacers
may comprises different materials, for example to provide composite
and/or locally adapted mechanical characteristics. Alternatively or
additionally, different materials may be used to provide a small
electro-chemical potential between the spacers, for example to
encourage bone growth. Alternatively or additionally, a small
voltage potential may be provided using a two layer material to
construct the spacer, with an isolator between the spacer layers.
Possibly, a voltage source is connected between the spacers, with
the circuit closed by body fluids.
[0413] Spiral Cut Spacer
[0414] FIG. 5 illustrates a spacer 150 in which slits 152 are
defined on the spacer in a spiral pattern. In this embodiment,
spacer 150 may be expand by applying a rotational force to the
spacer, rather than an axial force. In a preferred embodiment of
the invention, one end of the spacer is modified to grip bone, to
provide a suitable anchor for bone, for example as exemplified by a
pair of extensions 154. In a preferred embodiment of the invention,
extensions 154 fold out, for example as shown by dotted line 156,
to radially grasp the bone prior to the expansion of the spacer.
Preferably, the extensions are made of an elastic or super-elastic
material which is maintained in an axial configuration until the
spacer is inserted in place. Such anchoring may also be useful for
other embodiments of the invention, described herein. However, in
other preferred embodiments of the invention, no bone anchors are
provided, as the spacer can expanded in place without
anchoring.
[0415] Spike Variants
[0416] FIGS. 6A-6V illustrate variants of spikes and/or spike
orientations and/or spike layout patterns, in accordance with
alternative preferred embodiments of the invention.
[0417] Spike Side Profiles
[0418] FIGS. 6A-6K illustrate various spike side profiles (i.e.,
viewing from the side of the spacer), in accordance with preferred
embodiments of the invention. Generally, the profiles on both sides
of the spike match. However, in some preferred embodiments of the
invention, the profile may vary over the width of a spike. Thus, a
projection of the spike onto a plane perpendicular to the spike and
parallel to the spacer axis may yield a square shape, but may also
yield a triangle shape or a more complex shape, for example an
hourglass.
[0419] FIG. 6A illustrates a triangular profile, however, the tip
of the spike will usually be rounder.
[0420] FIG. 6B illustrates a rectangular profile.
[0421] FIG. 6C illustrates an inverse triangular profile.
[0422] FIG. 6D illustrates an hourglass profile. Profiles 6C and 6D
have the possible advantage of having a large area in contact with
adjacent bone. A possibly advantage of the spike of FIG. 6D is a
resistance to collapsing and the possibility of any collapsing
being partial, whereby the spike becomes shorter, rather than
completely collapsing. Another advantage of these inverted spikes
is that their inverted bases abut against adjacent spike's bases,
possibly stiffening the spacer.
[0423] FIG. 6E and FIG. 6F. illustrate two level spikes. One
possible advantage of such spikes is a is that the upper level
spike portion can collapse without affecting the lower level spike
portion. Another possible advantage is providing a lower portion of
a spike which can resist large loads and an upper portion of a
spike which better engages the adjacent bone tissue. Another
possible advantage of such spike is the provision of a greater
contact surface between the spike and the bone.
[0424] FIG. 6G illustrates an asymmetric spike. In addition, the
other spikes described herein may be constructed to be
asymmetric.
[0425] FIG. 6H illustrates a spike having portions which are below
a surface of the spacer.
[0426] FIG. 6I illustrates a spike which overhangs and which is at
a non-normal angle to the spacer. The angle maybe between
89.degree. and 20.degree., for example about 40.degree. about
60.degree., about 70.degree. or about 80.degree.. Alternatively or
additionally, the spike profile may be curved.
[0427] FIG. 6J illustrates a spike in which only one arm of the
spike is connected to the spacer. This spike form is preferably
manufacture by pre-loading such a strip to be extended and
maintaining the spike in a flat position until the spacer is
inserted and/or axially contracted. In a preferred embodiment of
the invention, when the spacer is shortened, the spike element is
above the surface of the spacer and, so, is guided by the surface
of the spacer to a more extended configuration. Possibly, the
surface of the spacer across the spike protrudes from the spacer,
to further urge this spike in a radial direction (rather than
allowing axial translation).
[0428] FIG. 6K illustrates a spike including a plurality of
sub-spikes.
[0429] Spike Orientation
[0430] FIGS. 6L-6N illustrate (using an axial view) variations in
an angle between the spike and the spacer, in a plane perpendicular
to the spacer axis. Although right-leaning spikes are shown, in
some preferred embodiments of the invention left leaning spikes are
used.
[0431] FIG. 6L illustrates a spike that is normal to the spacer
surface.
[0432] FIG. 6M illustrates a spike which is at an intermediate
angle to the spacer surface, for example between 10.degree. and
80.degree., for example about 30.degree., about 50.degree. or about
70.degree..
[0433] FIG. 6N illustrates a spike which is parallel to the spacer
surface.
[0434] FIGS. 6O-6S illustrate (using an axial view) variations in a
spike profile in the plane perpendicular to the spacer axis. It is
noted that variations in this profile of the spike may be affected
by cutting the spike-defining slit in the form of the desired
profile. Preferably, portions of the surface of the spacer are
removed so that the spike defining region has a rectangular form.
However, this is not required. Only the front profiles are shown.
Generally, the back profiles match the front profiles. However, the
front and back profiles may be different, in some preferred
embodiments of the invention.
[0435] FIG. 6O illustrates a rectangular profile.
[0436] FIG. 6P illustrates a trapezoid profile.
[0437] FIG. 6Q illustrates a triangular profile.
[0438] FIG. 6R illustrates an angled profile.
[0439] FIG. 6S illustrates a bent profile.
[0440] Spike Layouts
[0441] FIGS. 6T-6V illustrate spread layouts of spikes on the
surface of a collapsed spacer, in accordance with various preferred
embodiments of the invention. In the illustrations, the spacer is
expanded, axially slit, flattened, and viewed from above. The spike
locations are indicated as circles, even though, they may have
other forms when viewed from above, typically that of a rectangle.
The radial and/or axial and/or spatial density of spikes may vary
in some embodiments from what is shown in the figures.
[0442] FIG. 6T illustrates an alternating spike pattern, in which
the spikes are arranged in rings which have an angular offset
between them. The number of spikes per ring may be the same for all
the rings or may be different, periodically and/or as a function of
axial position. The pattern may also be viewed as a hexagonal grid
layout.
[0443] FIG. 6U illustrates an even spike distribution, arranged on
grid vertexes of a rectangular grid.
[0444] FIG. 6V illustrates a spike distribution in which the axial
spike density varies as a function of the axial location.
Alternatively or additionally, the radial density may vary as a
function of the axial position. Alternatively or additionally, the
radial density may vary as a function of the radial position.
Alternatively or additionally, the axial density may vary as a
function of the radial position.
[0445] Multi-leg Spikes
[0446] FIGS. 6W and 6X illustrate spikes that have more than two
legs. In particular a spike 300 of FIG. 6W has three legs: 302, 304
and 306. In FIG. 6X a spike 308 also has three legs: two legs 314
and one leg 312. A bar 310 connects the two legs 314 to leg 312. It
is noted than when spike 308 is extended (perpendicular to the
figure), bar 310 twists, rather then bending as in some of the
previously described spikes. An additional type of deformation
available is a pivot type deformation, in which a joint is defined
in the spacer. Possibly, such a joint is defined by using a
different material (or differently treated material) for the joint
than for the rest of the spacer. These types of deformations
(bending, twisting and pivoting) and/or other deformation types may
also be used for defining struts and wires. It is noted with
respect to FIG. 6X it is noted that the base of spike 308 may have
a zero width, for example if leg 312 moves axially to be between
legs 314.
[0447] Lift-up Spikes
[0448] FIGS. 6XA-6XC illustrate a lift-up mechanism, whereby a
spike (in this example a flat top spike) is lifted up from the
plane of the unexpanded spacer. FIG. 6XA is a side view, FIG. 6XB
is a perspective view and FIG. 6XC is a plan layout. Referring to
FIG. 6XB and to FIG. 6XG (below), when two ends 315 and 316 of the
spacer portion are brought together, legs 320 bend and a portion
318 of the spacer is lifted out of the spacer, in the direction of
the arrow. In a preferred embodiment of the invention, the legs 320
are weakened at their ends so that the legs bend only at the
weakened areas and/or in a direction dictated by the weakening.
[0449] FIGS. 6XD-6XH illustrate an alternative lift-up mechanism,
in which a plurality of legs 320' and a lifted up portion 318' are
substantially in a same hemisphere of the spacer, so that two
symmetrically opposing lift-up spikes may be fabricated on a single
spacer segment. FIG. 6XH is a plan layout of the spacer; FIGS. 6XD
and 6XE are side views of the collapsed spacer; and FIG. 6XF is a
perspective view of the collapsed spacer. FIG. 6XG, which is
equally applicable to FIGS. 6XA-6XC illustrates a side view of an
expanded spacer, with portion 318 lifted up form the spacer.
[0450] One advantage of the lifted up spikes is that they may
easily be formed of curved pieces of material, since the lifted up
part is not bent.
[0451] Another advantage of lift-up spikes is the ability to
provide a greater surface contact area, which contact area can be
smooth, rather than spiked.
[0452] Selective Weakening
[0453] FIGS. 6XI-6XL illustrate (using a side view, with an axial
portion of the spacer removed) examples of weakening of spacer
material to aid in achieving some exemplary spikes profiles of
those shown in FIGS. 6A-6K. The weakening illustrated are etching
and/or cutting of material in a direction perpendicular to the
spacer surface. However, weakening may also be achieved using other
means, for example, chemical or metallurgic treatment of by
drilling small holes, for example in joints. Addition, the
direction of the weakening may be at other orientations, for
example along the surface of the spacer (as in FIG. 6XA) or at an
angle thereto. Additionally or alternatively, the weakening and/or
strengthening of the spacer is applied to provide a preferential
distortion direction. FIG. 6XI shows a weakening pattern which aids
in achieving a symmetric spike. FIG. 6XJ shows a weakening pattern
which aids in achieving an asymmetric spike. FIG. 6XK shows a
weakening pattern which aids in achieving a flat top spike. FIG.
6XL shows a weakening pattern which aids in achieving an arc shaped
spike.
[0454] Spike Combinations
[0455] Although the above figures illustrate individual spacer
geometries, in some preferred embodiments of the invention,
geometries from two or more of the above figures may be combined in
a single spacer, possibly in a single spike. In addition, the
particular spike configuration selected may depend, inter alia, on
the intended use of the spacer. In particular, spike combinations
and/or configurations may be selected responsive to a desired
interaction between spikes, for example adjacent spikes leaning on
each other or engaging each other.
[0456] Protrusions
[0457] FIG. 7 schematically illustrates protrusions on a spacer
portion 400, in accordance with a preferred embodiment of the
invention. The portion is show in a side view and in a perspective
view. Portion 400 includes a spike 402 and a base portion (in some
cases a ring segment) 410. In a preferred embodiment of the
invention, a protrusion 404 and/or a protrusion 406 are provided to
increase the stiffness of spike 402 and/or prevent its collapse
under pressure. In the example of protrusion 404, spike 402 cannot
fold to the right, because protrusion 404 is blocking the movement.
In the example of protrusion 406, such movement is again blocked.
Protrusion 406 may have an alternative or additional function of
stiffening the spacer by filling in gaps between spike 402 and a
neighboring (axially and/or radially offset) spike 408.
[0458] In a preferred embodiment of the invention, the protrusions
are created by a variation in the thickness of the spacer.
Alternatively, a protrusion may comprise a portion of the tube
which folds out (or in). Preferably, the portion is manufactured to
be in an out position and is maintained in an "in" position, while
the spacer is collapsed, for example using an external collar.
Alternatively, the protrusion may be created by the expansion, for
example the protrusion comprising a small spike.
[0459] Axial Shrinkage Limitation
[0460] FIG. 8A illustrates a spacer 420 in which axial shrinkage of
the spacer is limited by the design of a tube portion 422 of the
spacer, in accordance with a preferred embodiment of the invention.
when spacer 420 is expanded, tube 422 axially contracts and spike
424 is extended. Additionally tube portions on either side of the
spike advance towards each other. These portions are marked as a
tab 428 and a tab 426 in the Figure. It is noted however, that only
one such tab is required, since the other tube portion may be flush
with the spike base or even back therefrom. When the two tabs meet,
further axial contraction is impossible or is severely restricted.
Further contraction, if it were to occur, would require either that
one of the tabs collapse or that one tab travels over the other
tab. As noted above with respect to FIG. 6J, such a tab may be
useful to guide the extension direction of a spike.
[0461] In a preferred embodiment of the invention, an adjustment to
mechanical characteristics of a spacer, for example tension, is
achieved by moving the one tab relative to the other, for example
using an externally applied needle, to allow them to continue their
axial movement. Additionally, one such axial motion is allowed, the
spacer may be further expanded.
[0462] It is noted that the final length and/or shape of the
expanded spacer and/or individual spikes thereon may be
considerably influenced by tabs 426 and 428. In a preferred
embodiment of the invention, a spacer is adapted for a particular
use by removing and/or bending such tabs so that they do or do not
impede axial compression. In one example, such tabs may be removed
in an operating room by a surgeon, after he makes final
measurements on an x-ray image. In another example, if a spacer did
not fit, the spacer is removed, adjusted and reinserted (or a new,
adjusted, spacer is inserted).
[0463] In a preferred embodiment of the invention, the distribution
of tabs 426 (and 428) is even over the length of the spacer.
Alternatively, an uneven axial distribution is provided.
Alternatively or additionally, an uneven radial distribution may be
provided. Alternatively or additionally, the length of the tabs is
different at different parts of the spacer. It is noted that an
un-even distribution of tabs on the spacer may cause the expanded
spacer to assume a bent configuration and/or for spikes to have
un-even lengths.
[0464] Alternative Axial Shrinkage Limitation
[0465] FIG. 8B illustrates an alternative embodiment of the
invention wherein a portion of a spacer 430 collapses upon itself
to limit axial contraction of the spacer. In a preferred embodiment
of the invention, such collapsing is achieved by weakening a strip
of spacer 430 at a plurality of locations, for example those
indicated by reference number 436. Preferably, the weakening
comprises a thinning of the material on the side of the fold.
Alternatively or additionally, the portion is pre-formed to be in a
shape of a wave, and maintained in an un-collapsed state either by
the un-extended spikes (e.g., before they are plastically deformed)
or by a restraining device (for example as described above with
reference to FIG. 2). Dotted line 438 indicates an extent of a
spike when the spacer is expanded.
[0466] In another embodiment of the invention, a spike extends into
the lumen of the spacer instead of out, thereby restricting axial
contraction of the spacer.
[0467] In the embodiments shown in FIGS. 8A and 8B, the axial
contraction restriction elements appear to be positioned instead of
a spike. Although this is possible, it is not required. In
alternative embodiments of the invention, at least some of the tabs
and/or wave-folded tube portions may be radially located between
spikes, for example, a radius including four spikes and four axial
contraction restriction elements. Alternatively or additionally, a
tab may be defined as part of the spike itself, for example as
indicated by dotted lines 427 and 429 in FIG. 8A.
[0468] Excavating Tool
[0469] FIG. 9A illustrates an excavating tool 450, in accordance
with a preferred embodiment of the invention. In a preferred
embodiment of the invention, tool 450 is used to pulverize a disc,
prior to insertion of a spacer. Tool 450 preferably comprises a
shaft 452 and a tip 454. In a preferred embodiment of the
invention, tip 454 comprises a radially expandable element, as
described above with reference to a spacer. Thus, the tool can be
inserted in a collapsed diameter and expanded only in the space
which is to be excavated. When shaft 452 is rotated, tip 454
rotates and pulverizes the disc material.
[0470] In a preferred embodiment of the invention, the entire tool
450 is made of a single material. Alternatively, a material with a
different hardness, stiffness and/or abrasion resistance may be
used for the tip. Alternatively or additionally, the sides and/or
ends of the spikes in tip 454 may be sharpened and/or coated with
an abrasive material, to assist in the pulverization.
[0471] FIG. 9B illustrates the tool of FIG. 9A, in which bent
configurations are shown using dotted lines, in accordance with a
preferred embodiment of the invention. Typically, the geometry of
the volume to be excavated does not have a circular cross-section.
In a preferred embodiment of the invention, shaft 452 may be bent,
at least in a vicinity 462 of tip 454, to allow a greater reach for
tip 454. Alternatively or additionally, tip 454 itself may bend. In
a preferred embodiment of the invention, the bending is achieved by
inserting a bent stylet 458 into a lumen 456 defined in shaft 452.
Alternatively, vicinity 462 is flexible and tip 454 is allowed to
freely bend.
[0472] In a preferred embodiment of the invention, stylet 458 is
not rotated with shaft 452, so that tip 454 is maintained in a
constant angle, for example maintaining tip 454 in a position 460.
Alternatively, the stylet and the shaft are rotated in
synchrony.
[0473] Alternatively or additionally, tool 454 may be bent by axial
contraction thereof. As indicated above, the axial contraction may
be uneven on the two sides of the spacer, for by reason of uneven
distribution of tabs 426 (FIG. 8A). In one example, a regular axial
contraction yields a straight tool tip. When the axial contraction
is increased (e.g., and more spikes are expanded and/or more tabs
abut), the tool bends in one direction, and when the contraction is
further increased, the tool bends in another, possibly opposite,
direction.
[0474] A lumen in tool 450 may have other uses, in some preferred
embodiments of the invention. These uses may use the same lumen as
lumen 456 or may require a separate lumen. The uses may be applied
while the shaft is rotating and/or while the shaft is at rest. One
use of such a lumen is to vacuum out the pulverized disc material.
Another use is for injecting fluids, for example, pharmaceuticals,
tissue softening materials and/or medical imaging contrast
materials. Alternatively or additionally, the lumen may be used to
provide a cutting action, for example by providing laser light, a
knife edge, cryosurgery tools, RF coils or electric cutters through
the lumen. Alternatively or additionally, a high pressure flow of
abrasive material may be provided. Alternatively or additionally,
the lumen may be used to provide endoscopic surgery tools and/or
tissue connectors, such as clips or staples. Alternatively or
additionally, the lumen may be used to provide an imaging means,
such as an optical viewing means or an ultrasonic viewing means.
Alternatively or additionally, a spacer may be provided and/or
expanded and/or collapsed through the lumen. Optionally, in one
preferred embodiment of the invention, the tool itself may be
further expanded and used as a spacer, after the disc is
removed.
[0475] The above uses of a lumen may also be practiced on a spacer,
in accordance with some preferred embodiments of the invention. In
particular, a tool 450 may be provided through a spacer. In another
example, a second spacer may be inserted past a first spacer, by
passing a member 60 of the second spacer through the expanded
spacer.
[0476] Alternative Uses for Spacer Geometry
[0477] As described above, the expandable spacer is especially
suitable for spinal fusion. However, a similar geometry device may
have other uses. One type of usage is as a bone fixation device,
for example fulfilling the general requirements described in the
above referenced PCT publication WO 98/38918. FIG. 10A illustrates
a bone 700 with a fracture location 702 into which a spacer 704 (in
this example being used as a bone fixator) is being inserted. An
optional elongate member 706 may be a guide or may for an extension
of the spacer, for example as described herein above with reference
to FIG. 2. It is noted that the spacer of the present invention, in
some embodiments thereof may be inserted through a small hole in a
bone, possibly without open surgery. Optionally, the spacer
includes an outside thread, at least at its tip, so that the spacer
can be screwed into the bone. Preferably, the spacer may also be
removed through the same or a new hole made in the bone, preferably
without requiring an open surgical incision. Optionally, as shown
in FIG. 10B, when the insertion of the spacer is completed, a
flared opening 708 is maintaining in the bone, possibly by an
extension of the spacer, to aid in adjusting and/or removing the
spacer. Alternatively, it is noted that the spacer does not usually
block a large volume of the bone, so it may not be required to
remove it. FIG. 10C illustrates the insertion of a spacer into a
bent bone 710, for example a rib. Also, it is noted that such a
spacer may be inserted into a small bone, for example a finger
bone.
[0478] Dental Implant
[0479] FIG. 11 is an exploded view of a dental implant 600 in
accordance with a preferred embodiment of the invention. A tooth is
missing in a jaw 601, leaving behind a hole 602. In a preferred
embodiment of the invention, an expandable spacer 604 is inserted
into the hole and expanded therein, to form a support for a dental
cap 606. Preferably, a filler material, such as powdered bone or
tooth material is used to fill hole 602. Alternatively or
additionally to forming a complete support for a dental cap, an
expandable spacer may be used to fill-in a space between a support
and the walls of hole 602. Alternatively or additionally, an
expandable spacer may be used to replace a single root of a
multi-root natural tooth. It is noted that bone tissue, tooth
material, nervous tissue and/or blood vessels may grow into the
hollows of spacer 604. Optionally, an inner support is also
inserted into the spacer, to strengthen it, for example a screw as
described above with reference to FIG. 2.
[0480] Soft Tissue Connector
[0481] FIGS. 12A-12C illustrate the use of an axially contracting
tissue fastener 610, in accordance with a preferred embodiment of
the invention. A tissue 612 is to be fastened to tissue 614. A tip
611, preferably sharp, possibly barbed or curved, of fastener 610
preferably penetrates the two tissues, as shown in FIG. 12A. It is
noted that fastener 610 may be narrow and/or flexible, thus being
suitable for application using a catheter, an endoscope and/or
using an external syringe-like device.
[0482] In FIG. 12B, a first set of spikes 616 and/or a second set
of spikes 618 are preferably extended, to stop the tissues from
moving away from each other. In the case that only one set of
spikes is extended, for example spikes 616, the fastener may be
axially moved, for example in the direction of arrow 620, in order
to bring the two tissue together. It should be noted that tissue
612 and/or tissue 614 may have a considerable thickness. In such a
case the spikes will preferably expand into the tissue, instead of
behind it as shown in FIG. 12B. However, the function of engaging
the tissue will preferably be performed.
[0483] In FIG. 12C, the rest of fastener 610 is axially contracted,
bringing the two tissues in close proximity. The width of an
intermediate section 622 of the fastener may depend on the distance
between the tissue when spikes 6161 and 618 are expanded and/or it
may depend on whether or not the fastener is moved during the
procedure. However, in general, the distance between the two
tissues will be considerable smaller than in FIG. 12A and the two
tissue will be coupled by section 622, preferably to allow little
or no relative motion. Optionally, the fastener (or a spacer, as
described above) is formed of a plurality of links which can rotate
one relative to the other. Thus, the two attached soft tissue can
rotate one relative to each other, if each is grasped by a
different link of the spacer. In a preferred embodiment of the
invention, each such link may be expanded or collapsed
separately.
[0484] As described above, the spikes of fastener 610 are
preferably expanded in a certain order. However, the action of
FIGS. 12A-C will occur also if all the spikes are expanded at the
same time. Generally, after a short axial contraction, spikes 616
will expand enough so that they will not retract through the hole
made in tissue 612 by tip 611. Although further axial contraction
will increase the tension on the hole (by stretching/moving tissue
612) it will also increase the spike size, so retraction of the
spikes is unlikely.
[0485] In a preferred embodiment of the invention, exact placement
of fastener 610 is not required, since once tissues 612 and 614 are
skewered by fastener 610 and are each located between two spike
positions, further axial contraction of the fastener will
invariably engage the tissues and bring them together.
[0486] In some preferred embodiments of the invention, the spikes
in section 622 are longer than in the rest of fastener 610,
allowing a greater axial contraction. It is noted that, in some
applications, it is desirable to allow some "free" space between
the fastened soft tissues.
[0487] In a preferred embodiment of the invention, once the process
of FIGS. 12A-12C is complete, fastener 610 is disengaged at its end
624 from a member (not shown) which was holding it in place.
Alternatively, fastener 610 comprises an elastic or super elastic
element which is injected into a tissue and allowed to self-expand,
without being held by a member. Alternatively fastener 610 may
comprise a portion of a continuously extruded fastener. When
required to fasten soft tissue, a short segment of the fastener is
used as in FIGS. 12A-12C and then the remainder of the fastener is
cut off. Thus, multiple fastening activities may be performed with
a minimum required diameter and a minimum of tool exchanging and/or
toll motion.
[0488] As an alternative embodiment (not shown) a single spike may
span spikes 616 and 618. Referring back to FIG. 2K (multi-sub-spike
spike example) a single spike may include two or more sub spikes,
for example a sub-spike 616 and a sub-spike 618. When such a single
spike partially extends, the two sub spikes engage the soft
tissues. As the spike continues to extend (axial compression of the
fastener) each of the sub spikes increases in radial extent and is
brought closer together. Such behavior may be controlled by
suitable weakening of the spikes, as described above, for example
with reference to FIG. 6XI, noting however, that if a spike is
weakened by different amounts in different locations, the weaker
location will typically fold first and then the strongest location,
when axial compression is applied.
[0489] Alternatively to fastening soft tissue to soft tissue, a
fastener similar to fastener 610 may be used for attaching soft
tissue to bone. In one example, if tip 611 comprises a bone anchor,
the process of FIGS. 12A-C may be performed to attach tissue 614 to
a bone 612, except that there is generally no need to expand spikes
616 in the bone. Alternatively, spikes 616 are expanded a small
amount, to better hold the bone. Alternatively, spikes 616 are
expanded by a large amount, for example if tip 611 passes through a
cortical portion of the bone into a trabecular portion thereof.
[0490] Additionally or alternatively, to fastening soft tissue to
bone, a similar fastener may be used to attach a bone to a bone
and/or to apply attractive forces between two bones. In this
embodiment, it may be unnecessary for the spikes to extend when the
spacer is axially shortened. In a preferred embodiment of the
invention, a spike shape as shown in FIG. 6K is used, in which the
spikes extend a minimal amount. Alternatively, the spikes may
"extend" into the lumen, preferably using a spike profile which is
the inverse of that of FIG. 6K.
[0491] Space Filling Using a Spacer
[0492] Another possibly use of the expanding spacer is to fill
intra body cavities and/or change mechanical properties of body
tissues, for example stiffness, elasticity, minimum compressed
dimension. For example, such a spacer may be used to stiffen a
intra-vertebral disc. Additionally or alternatively, such a spacer
is used as a framework for new tissue growth. Additionally or
alternatively, such a spacer is used to enhance drainage. Changing
the mechanical properties of body tissue may also be used for
cosmetic purposes, for example to reduce sagging and to disguise
flabby flesh.
[0493] In some such cases, the spacer is composed, at least in
part, of softer, thinner and/or more flexible materials than
described with reference to FIGS. 4A-4C. In one example, the spacer
is made of plastic. In another example, the spacer comprises
polymer coated metal.
[0494] Another possible use of such a spacer is for opening crushed
or otherwise blocked air passageways. One advantage of some
embodiments of the above spacer is that they are inherently
non-blocking, if for example a spacer fails to open properly.
[0495] External Control of Spacer Geometry
[0496] In a preferred embodiment of the invention, a spacer, for
example as described above, can be controlled from outside the
body, after it is inserted. In one example, referring back to FIG.
2J, screw 124 may be turned by coupling a magnetic force from
outside the body, for example if a small permanent magnet is
coupled to the screw. When a strong permanent magnet is rotated
outside the body, torque is applied to the small magnet, turning
the screw. In another example, externally applied magnetic and/or
electric fields may be used to control a pressure valve, which
valve allows pressurized fluid to inflate or deflate a balloon,
thereby axially and/or radially expanding or collapsing the spacer.
In some embodiments, the control of spacer expansion uses logic
(electrical or mechanical) which is integrated into the spacer, for
example, to periodically axially compress the spacer. The power
and/or control signals may be supplied from inside the body or from
a power source (or computer) outside the body.
[0497] It will be appreciated that the above described apparatus
and methods of expandable inserts may be varied in many ways. In
addition, a multiplicity of various features, both of methods and
of devices have been described. It should be appreciated that
different features may be combined in different ways. In
particular, not all the features shown above in a particular
embodiment are necessary in every similar preferred embodiment of
the invention. Further, combinations of the above features are also
considered to be within the scope of some preferred embodiments of
the invention. It should also be appreciated that many of the
embodiments are described only as methods or only as apparatus,
however the scope of the invention includes both methods for using
apparatus and apparatus for applying the methods. The scope of the
invention also covers machines for creating the apparatus described
herein. In addition, the scope of the invention includes methods of
using, constructing, calibrating and/or maintaining the apparatus
described herein. Section headings where they appear are meant for
clarity and ease of browsing the application and are not to be
construed as limiting the applicability of subject matter described
within. When used in the following claims or in the text above, the
terms "comprises", "comprising", "includes", "including" or the
like mean "including but not limited to".
* * * * *