U.S. patent application number 10/699618 was filed with the patent office on 2004-07-22 for movable disc implant.
Invention is credited to Krueger, David J., Wagner, Erik J..
Application Number | 20040143332 10/699618 |
Document ID | / |
Family ID | 32312554 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040143332 |
Kind Code |
A1 |
Krueger, David J. ; et
al. |
July 22, 2004 |
Movable disc implant
Abstract
A disc implant is provided which maintains intervertebral
spacing and stability within the spine. In an embodiment, a disc
implant may include three or more components. Components of the
implant may imitate certain physiological movements associated with
a healthy spine. In certain embodiments, the components of the
implant may limit physiological movements to within certain ranges,
imitating normal spinal movements.
Inventors: |
Krueger, David J.; (Cedar
Park, TX) ; Wagner, Erik J.; (Austin, TX) |
Correspondence
Address: |
MEYERTONS, HOOD, KIVLIN, KOWERT & GOETZEL, P.C.
P.O. BOX 398
AUSTIN
TX
78767-0398
US
|
Family ID: |
32312554 |
Appl. No.: |
10/699618 |
Filed: |
October 31, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60422764 |
Oct 31, 2002 |
|
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Current U.S.
Class: |
623/17.14 ;
606/90; 623/17.15 |
Current CPC
Class: |
A61F 2/4684 20130101;
A61F 2002/30649 20130101; A61F 2002/4622 20130101; A61F 2250/0075
20130101; A61B 17/1604 20130101; A61F 2002/30378 20130101; A61F
2002/30695 20130101; A61F 2002/3071 20130101; A61F 2002/4681
20130101; A61F 2230/0073 20130101; A61F 2002/4627 20130101; A61F
2002/30451 20130101; A61F 2002/30828 20130101; A61F 2002/30448
20130101; A61B 17/025 20130101; A61B 17/1757 20130101; A61B
2090/062 20160201; A61F 2002/30639 20130101; A61F 2250/0089
20130101; A61F 2230/0004 20130101; A61F 2310/00017 20130101; A61F
2002/4628 20130101; A61F 2/4425 20130101; A61F 2002/30879 20130101;
A61F 2002/30878 20130101; A61F 2310/00976 20130101; A61F 2310/00029
20130101; A61F 2002/30528 20130101; A61F 2002/30365 20130101; A61F
2250/0064 20130101; A61F 2002/30617 20130101; A61F 2220/005
20130101; A61B 90/94 20160201; A61B 2017/0256 20130101; A61F
2002/30845 20130101; A61F 2002/30841 20130101; A61F 2220/0025
20130101; A61F 2250/0087 20130101; A61F 2310/00796 20130101; A61F
2002/30252 20130101; A61F 2310/00023 20130101; A61F 2002/30616
20130101; A61F 2002/3008 20130101; A61F 2002/30884 20130101; A61F
2002/443 20130101; A61F 2220/0058 20130101; A61F 2002/30062
20130101; A61F 2002/30112 20130101; A61F 2210/0004 20130101; A61F
2002/30823 20130101; A61F 2220/0033 20130101; A61F 2250/0097
20130101; A61B 17/1671 20130101; A61F 2/4611 20130101; A61F
2002/30383 20130101; A61F 2002/30891 20130101; A61F 2002/30662
20130101; A61F 2/30767 20130101; A61F 2250/0098 20130101; A61F
2310/00407 20130101 |
Class at
Publication: |
623/017.14 ;
623/017.15; 606/090 |
International
Class: |
A61F 002/44; A61F
002/46 |
Claims
What is claimed is:
1. An artificial disc implant for a human spine, comprising: two
engaging plates, wherein each engaging plate comprises: a recess;
and two or more slots configured to engage an insertion instrument
during insertion of the disc implant, wherein the slots are at an
angle relative to an anterior-posterior axis of the engaging
plates; and one or more members positionable between the engaging
plates, wherein at least one of the members comprises a portion
configured to complement at least one of the recesses to allow
axial rotation, lateral movement and anteroposterior movement of
the engaging plates relative to each other during use.
2. The implant of claim 1, wherein one or more sides of at least
one of the recesses are tapered.
3. The implant of claim 1, wherein a height of a posterior side
exceeds a height of an anterior side of at least one of the
recesses.
4. The implant of claim 1, wherein the portion configured to
complement at least one of the recesses is a convex portion, and
wherein at least one of the recesses comprises a concave portion
complementary to the convex portion.
5. The implant of claim 1, wherein at least one of the engaging
plates comprises a convex portion, wherein at least one of the
members comprises a concave portion, and wherein the convex portion
is complementary to the concave portion.
6. The implant of claim 1, wherein the two engaging plates and the
one or more members are made of metal.
7. The implant of claim 1, wherein the slots are dovetailed.
8. A system for inserting an artificial disc implant between human
vertebrae, comprising: an inserter having a body, a passage through
the body, and arms, wherein the arms are configured to be
releasably coupled to engaging plates of the artificial disc
implant; and a distractor positionable in the passage in the body,
wherein the distractor is configured to separate the arms of the
inserter such that engaging plates coupled to the arms of the
inserter remain substantially parallel during separation of the
engaging plates to form a disc space between the human
vertebrae.
9. The system of claim 8, wherein the inserter is configured such
that coupling the inserter to the engaging plates does not increase
separation between the engaging plates.
10. The system of claim 8, wherein the arms of the inserter are
configured to be releasably coupled to dovetailed slots in the
engaging plates.
11. The system of claim 8, wherein the inserter and the distractor
are configured such that the distractor does not contact the
engaging plates during insertion of the engaging plates.
12. The system of claim 8, further comprising a pusher, wherein the
pusher is configured to drive a member through a passage in the
distractor and position the member between the engaging plates.
13. The system of claim 8, further comprising a member seater
configured to seat a member in the engaging plates through the
passage in the inserter.
14. The system of claim 8, further comprising trial endplates and
one or more additional distractors, wherein the trial endplates are
configured to be used in combination with the distractors to
determine height and lordotic angle of the artificial disc implant
to be inserted.
15. A method for forming an artificial disc implant between human
vertebrae, comprising: positioning two engaging plates between the
human vertebrae; separating the engaging plates such that the
engaging plates remain substantially parallel; positioning one or
more members between the engaging plates such that a surface of at
least one of the members contacts a complementary surface of at
least one of the engaging plates; and wherein the engaging plates
and at least one of the members are configured to allow relative
movement of the engaging plates during use.
16. The method of claim 15, further comprising determining a
height, size and lordotic angle of the artificial disc implant to
be formed between the vertebrae before positioning the engaging
plates between the vertebrae.
17. The method of claim 15, further comprising forming a recess in
at least one of the vertebrae to engage a projection on at least
one of the engaging plates.
18. The method of claim 15, wherein positioning at least one of the
members comprises positioning such members in a rounded recess in
at least one of the engaging plates.
19. The method of claim 15, wherein the engaging plates are
positioned using an angulated anterior approach to the
vertebrae.
20. The method of claim 15, wherein the engaging plates are
positioned using an anterior approach to the vertebrae.
21. A disc implant, comprising: a first engaging plate and a second
engaging plate; a member positionable between the engaging plates;
wherein the first engaging plate comprises a recess configured to
receive a base of the member, wherein one or more sides of the
recess are tapered; and wherein a surface of the second engaging
plate complements a surface of the member to allow axial rotation,
lateral movement and anteroposterior movement of the engaging
plates relative to each other during use.
22. The implant of claim 21, wherein a height of a posterior side
of the recess is greater than a height of an anterior side of the
recess.
23. The implant of claim 21, wherein at least one of the engaging
plates comprises a concave portion complementary to a convex
portion of the member.
24. The implant of claim 21, wherein at least one of the engaging
plates comprises a convex portion complementary to a concave
portion of the member.
25. The implant of claim 21, wherein at least one of the engaging
plates comprises at least one coupling projection.
26. The implant of claim 21, wherein the engaging plates comprise
one or more slots, wherein the slots are configured to engage an
instrument for insertion of the implant.
27. The implant of claim 21, wherein the engaging plates comprise
one or more slots wherein the slots are configured to engage an
instrument for insertion of the implant and wherein the slots are
positioned at an angle relative to anterior-posterior axes of the
engaging plates.
28. A system for inserting an artificial disc implant, comprising:
an inserter having a body, a passage through the body and arms,
wherein the arms are configured to be releasably coupled to
engaging plates of the artificial disc implant; and one or more
distractors positionable through the passage in the body, the
distractors configured to move the arms to establish a separation
distance between engaging plates coupled to the arms.
29. The system of claim 28, further comprising a pusher configured
to drive a member down a passage through the distractor to a
position between the engaging plates.
30. The system of claim 28, further comprising a member seater
configured to seat a member between the engaging plates.
31. The system of claim 28, further comprising trial endplates,
wherein the trial endplates in combination with at least one
distractor are configured to determine height and lordotic angle of
the artificial disc implant to be inserted.
32. An instrument kit, comprising: one or more trial endplates; a
plurality of implant components; and an inserter configured to
couple to selected implant components to allow the components to be
positioned in a disc space; one or more distractors configured to
couple to the inserter to establish a separation distance between
the selected implant components coupled to the inserter.
33. The instrument kit of claim 32, wherein the inserter is
configured to couple to the trial endplates.
34. The instrument kit of claim 32, wherein one or more of the
trial endplates are sloped.
35. The instrument kit of claim 32, further comprising a pusher
configured to position an implant component between the selected
implant components coupled to the inserter.
36. The instrument kit of claim 32, further comprising a member
seater, wherein the member seater is configured to apply pressure
to one of the implant components.
37. The instrument kit of claim 32, further comprising a pusher
configured to position an implant component between the selected
implant components coupled to the inserter.
38. A method for forming an implant between vertebrae of a spine,
comprising: coupling a pair of engaging plates to a portion of an
inserter; positioning the engaging plates between adjacent
vertebrae; positioning one or more members between the engaging
plates; and wherein at least a portion of the engaging plates and
at least a portion of at least one member is configured to allow at
least some movement of a first vertebra relative to a second
vertebra.
39. The method of claim 38, wherein positioning the engaging plates
comprises an anterior approach to the vertebrae.
40. The method of claim 38, wherein positioning the engaging plates
comprises an angled anterior approach to the vertebrae.
41. The method of claim 38, further comprising positioning a
distractor in the inserter wherein the distractor is configured to
separate in a substantially parallel direction one engaging plate
from a second engaging plate.
42. The method of claim 38, further comprising positioning a
distractor in the inserter wherein the distractor is configured to
separate one engaging plate from a second engaging plate and
wherein positioning a member of the one or more members between the
engaging plates comprises guiding the member through the distractor
with a pusher.
43. The method of claim 38, wherein the movement comprises at least
axial rotation and lateral movement of the spine.
44. The method of claim 38, further comprising inserting one or
more trial implants and one or more distractors in the vertebral
space before coupling the engaging plates to the inserter to
determine a lordotic angle of the engaging plates and a height of
the members to be inserted.
45. An instrument for insertion of a disc implant, comprising: a
body; one or more arms configured to couple to one or more engaging
plates; a distractor positionable in an opening of the body,
wherein the distractor is configured to separate in a substantially
parallel direction one engaging plate from a second engaging plate.
Description
PRIORITY CLAIM
[0001] This application claims priority to U.S. Provisional Patent
Application No. 60/422,764 entitled "MOVABLE DISC IMPLANT" filed on
Oct. 31, 2002. The above-referenced provisional application is
incorporated by reference as if fully set forth herein.
BACKGROUND
[0002] 1. Field of Invention
[0003] The present invention generally relates to the field of
medical devices. Some embodiments of the invention relate to spinal
disc implants and instruments used to insert the implants. Other
embodiments of the invention relate to methods of forming spinal
disc implants and methods for positioning the implants during
surgical procedures.
[0004] 2. Description of Related Art
[0005] Bone may be subject to degeneration caused by trauma,
disease and/or aging. Degeneration may destabilize bone and affect
surrounding structures. For example, destabilization of a spine may
result in alteration of a natural spacing between adjacent
vertebrae. Alteration of a natural spacing between adjacent
vertebrae may subject nerves that pass between vertebral bodies to
pressure. Pressure applied to the nerves may cause pain and/or
nerve damage. Maintaining the natural spacing between vertebrae may
reduce pressure applied to nerves that pass between vertebral
bodies. A disc implant may be used to maintain the natural spacing
between vertebrae and to inhibit relative motion of the
vertebrae.
[0006] A disc space may be created by full or partial removal of an
intervertebral disc between two vertebral bodies. Spinal implants
for a lumbar region of the spine may be positioned in an
intervertebral space after a discectomy procedure. The implant may
be inserted using an anterior, lateral and/or posterior approach.
The spinal implant may be a fusion device or an artificial disc.
Conventional systems and methods for posterolateral spinal fusion
may involve dissecting and retracting soft tissue proximate the
surgical site. Dissection and retraction of soft tissue may cause
trauma to the soft tissue and extend recovery time. Minimally
invasive procedures and systems may reduce recovery time as well as
trauma to the soft tissue surrounding a stabilization site.
[0007] Spinal disc implants and/or disc implant insertion
instruments are described in U.S. Pat. No. 5,676,701 to Yuan et
al.; U.S. Pat. No. 5,401,269 to Buttner-Janz et al.; U.S. Pat. No.
5,370,697 to Baumgartner; U.S. Pat. No. 5,314,477 to Marnay and
International Application No. WO 01/19295 to Marnay, all of which
are incorporated by reference as if fully set forth herein.
SUMMARY
[0008] In certain embodiments, a disc implant may be used to
stabilize vertebrae of a human spine while allowing normal movement
of the vertebrae relative to each other. An artificial disc implant
may replace a diseased or defective intervertebral disc. An
artificial disc implant may be easy to install with only minimal
intrusion to adjacent tissue and muscle. A disc implant may
introduce minimal risk of dural damage or neural damage during
installation and use.
[0009] An artificial disc implant may include one or more engaging
plates and one or more members. Engaging plates may fit between and
engage adjacent vertebrae of the spine. The plates may maintain a
space between the adjacent vertebrae. One or more members may be
positioned in the space between the engaging plates. Engaging
plates and members may be designed to allow axial rotation,
anteroposterior movement and/or lateral movement of adjacent
vertebrae (i.e., the spine). Lateral movement may include lateral
bending. Anteroposterior movement may include flexion and/or
extension. In some embodiments, a range of motion of one engaging
plate relative to another engaging plate may be limited.
[0010] In some embodiments, an engaging plate may include a recess
complementary to a portion of a member. In certain embodiments, an
engaging plate may include slots. The slots may be dovetailed. The
slots may be complementary to a portion of an instrument used to
insert engaging plates between vertebrae. In some embodiments,
slots may be formed at an angle relative to an anterior-posterior
axis of an engaging plate. In some embodiments, an angular
orientation of a recess may correspond to an angle of slots in an
engaging plate. Angulation of the slots may allow insertion of a
disc implant using a modified (e.g., angulated) anterior approach.
A modified anterior approach may facilitate retraction of blood
vessels above the L5 vertebrae.
[0011] In certain embodiments, an engaging plate may include one or
more coupling projections. One or more coupling projections may
penetrate a vertebral surface. In some embodiments, a coupling
projection may be positioned in a recess formed in a vertebral
surface. Once positioned in the vertebra, the coupling projection
may inhibit movement of an engaging plate relative to the
vertebra.
[0012] In some embodiments, a disc implant may include two engaging
plates and a member. The member may have a convex portion. The
engaging plates may be shaped to complement surfaces of the member,
including the convex portion. The member may be positioned between
the engaging plates to allow axial rotation, lateral and/or
anteroposterior movement of a first engaging plate relative to a
second engaging plate.
[0013] In disc implant embodiments including two engaging plates
and a member, the member may allow the engaging plates to undergo
three independent components of motion relative to each other. The
member may have a convex portion and a recess. The recess of the
member may complement a projection on a first engaging plate to
allow rotation of a first engaging plate relative to the member.
The convex portion of the member may complement a concave portion
of the second engaging plate to allow anteroposterior and/or
lateral movement of the second engaging plate relative to the
member.
[0014] In some embodiments, a disc implant may include two engaging
plates and two members. The members may allow the engaging plates
to undergo three independent components of motion relative to each
other. A convex portion of a first engaging plate may complement a
concave portion of a first member to allow lateral bending of the
first engaging plate relative to a second engaging plate. A
projection on the first member may complement a recess in a second
member to allow axial rotation of the first engaging plate relative
to the second engaging plate. A convex portion of the second member
may complement a concave portion of the second engaging plate to
allow movement of the engaging plates relative to each other.
[0015] In other disc implant embodiments including two engaging
plates and two members, a first member may couple to a first
engaging plate to allow axial rotation of the first engaging plate
relative to a second engaging plate. A convex portion of the first
member may complement a concave portion of a second member to allow
lateral bending of the engaging plates relative to each other. A
convex portion of the second member may complement a concave
portion of the second engaging plate to allow flexion and/or
extension of vertebrae adjacent to the engaging plates.
[0016] In disc implant embodiments including a member and two
engaging plates, a member may have a spherical shape. The member
may be positioned between concave portions of the engaging plates.
The member may allow axial-rotation, anteroposterior movement
and/or lateral movement of the engaging plates relative to each
other.
[0017] An instrumentation set for a disc implant insertion
procedure may include various guidance and/or insertion
instruments. Insertion instruments may include, but are not limited
to, chisels, reamers, hex drivers, slap hammers, inserters,
distractors and pushers. An instrumentation set may include trial
endplates and disc implant components. Trial endplates may be
plates of various sizes and lordotic alignment. Trial endplates may
include stops and/or instrument guides to facilitate removal of
bone material from a vertebral surface. Distractors in combination
with trial endplates may determine a size, height and lordotic
alignment of implant components to be used in a disc implant
insertion procedure. Implant components may include, but are not
limited to, engaging plates of various sizes and lordotic alignment
and members of various sizes and shapes.
[0018] An inserter may be used to position engaging plates between
two vertebrae. A distractor may be positioned between the engaging
plates to establish a desired separation distance between the
engaging plates. One or more members may be guided through a body
of the distractor and into the space between the engaging plates.
In some embodiments, members may be guided through a body of a
distractor with a pusher. The pusher may maintain the position of
the members when a distractor is removed from the inserter.
[0019] In certain embodiments, trial endplates, members and
engaging plates may be formed from various materials including
plastics, ceramics, polymers, composites and metals. Materials may
be chosen based on factors including, but not limited to,
durability, biocompatibility, galling characteristics, mechanical
strength and/or wear properties. In some embodiments, radiological
markers may be used in combination with materials that are
"invisible" to radiological techniques. In certain embodiments,
steps may be taken to adjust a coefficient of friction of materials
chosen to form members (e.g., surfaces may be polished or
roughened). In other embodiments, surfaces of engaging plates
and/or members may be coated to reduce noise created by contact of
a member with an engaging plate and/or another member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Advantages of the present invention will become apparent to
those skilled in the art with the benefit of the following detailed
description and upon reference to the accompanying drawings in
which:
[0021] FIG. 1 is a perspective view of components of a disc
implant.
[0022] FIG. 2 is a bottom view of an embodiment of an engaging
plate.
[0023] FIG. 3 is a bottom view of an embodiment of an engaging
plate.
[0024] FIG. 4 is a cross-sectional view of an embodiment of a disc
implant.
[0025] FIG. 5 is a side view of components of a disc implant.
[0026] FIG. 6 is a perspective view of components of a disc
implant.
[0027] FIG. 7 is a cross-sectional view of an embodiment of a disc
implant.
[0028] FIG. 8 is a bottom view of an engaging plate.
[0029] FIG. 9 is a perspective view of components of a disc
implant.
[0030] FIG. 10 is a cross-sectional view of an embodiment of a disc
implant.
[0031] FIG. 11 is a perspective view of components of a disc
implant.
[0032] FIG. 12 is a top view of a member.
[0033] FIG. 13 is a cross-sectional view of an embodiment of a disc
implant.
[0034] FIG. 14 is a perspective view of components of a disc
implant.
[0035] FIG. 15 is a cross-sectional view of an embodiment of a disc
implant.
[0036] FIG. 16 is a perspective view of components of a disc
implant.
[0037] FIG. 17 is a cross-sectional view of an embodiment of a disc
implant.
[0038] FIG. 18 is a perspective view of components of a disc
implant.
[0039] FIG. 19 is a cross-sectional view of an embodiment of a disc
implant.
[0040] FIG. 20 is a side view of an embodiment of a disc
implant.
[0041] FIG. 21 is a perspective view of an embodiment of a disc
implant.
[0042] FIG. 22 is a cross-sectional view of an embodiment of a disc
implant.
[0043] FIGS. 23-27 depict embodiments of coupling projections.
[0044] FIG. 28 is a perspective view of an embodiment of an
inserter.
[0045] FIG. 29 is a side view of a portion of an embodiment of an
inserter coupled to engaging plates.
[0046] FIG. 30 is a side view of an embodiment of an inserter.
[0047] FIG. 31 is a perspective view of an embodiment of a slap
hammer coupled to an inserter.
[0048] FIG. 32 is a perspective view of an embodiment of a
distractor.
[0049] FIG. 33 is a perspective view of an embodiment of a
distractor positioned in an inserter.
[0050] FIG. 34 is a perspective view of an embodiment of a
pusher.
[0051] FIG. 35 is a side view of an embodiment of a pusher coupled
to an inserter.
[0052] FIG. 36 is a perspective view of an embodiment of an
instrument guide.
[0053] FIG. 37 is a perspective view of an instrument guide coupled
to an inserter
[0054] FIG. 38 and FIG. 38A depict an embodiment of a chisel.
[0055] FIG. 39 is a perspective view of a chisel in working
relation to an instrument guide.
[0056] FIG. 40 is a perspective view of a reamer in working
relation to an instrument guide.
[0057] FIG. 41 depicts embodiments of trial spacers.
[0058] FIG. 42 is a bottom view of an embodiment of a trial
endplate.
[0059] FIG. 43 is a perspective view of a member seater.
[0060] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are shown by
way of example in the drawings and will herein be described in
detail. The drawings may not be to scale. It should be understood
that the drawings and detailed description thereto are not intended
to limit the invention to the particular form disclosed, but on the
contrary, the intention is to cover all modifications, equivalents
and alternatives falling within the spirit and scope of the present
invention as defined by the appended claims.
DETAILED DESCRIPTION
[0061] An intervertebral disc implant may be used to stabilize a
portion of the spine. The artificial intervertebral disc implant
may replace all or a portion of an intervertebral disc that
requires replacement due to degeneration from natural wear, trauma
or disease. The artificial intervertebral disc may restore the
normal separation distance between the vertebrae and allow normal
movement and flexibility of the spine.
[0062] Disc implants may allow movement of adjacent vertebrae
relative to each other in ranges associated with normal limits for
human vertebrae. Disc implants may allow axial rotation, axial
compression and lateral and/or anteroposterior movement. In a human
spine, axial rotation may include rotation of about 0.1.degree. to
about 3.degree. about a longitudinal axis of the spine. An axis of
rotation between vertebrae may be off-center due to the
fibrocartilaginous nature of an intervertebral disc. An axis of
rotation between two vertebrae may be located posterior to a
mid-point between the vertebrae. Lateral movement may include
lateral bending. Lateral bending may include motion to the left
and/or right up to a maximum of about 0.5.degree. to about
10.degree.. Anteroposterior movement may include flexion and/or
extension. Flexion may include anterior motion up to a maximum of
about 0.5.degree. to about 20.degree.. Extension may include
posterior motion up to a maximum of about 0.5.degree. to about
10.degree..
[0063] Some implant embodiments may inhibit movement outside of
normal limits for vertebrae. Limiting a range of motion may
decrease chances of injury. Tissue and structure adjacent to
vertebrae separated by a disc may limit some ranges of motion. For
example, surrounding tissue and structure may limit axial rotation
of vertebrae.
[0064] In some embodiments, artificial disc implants may be used to
replace a disc or discs in the lumbar region of a spine. In certain
embodiments, artificial disc implants may be used in cervical or
thoracic portions of the spine. In some embodiments, artificial
disc implants may be used with other systems or devices to provide
stability to the spine. In other embodiments, a disc implant may be
used as a stand-alone system.
[0065] FIG. 1 is a perspective view of components of an embodiment
of a disc implant that may be inserted between two vertebrae. Disc
implant 100 may include engaging plate 102, member 104 and engaging
plate 106. When the implant is installed in a patient, each
engaging plate of the implant may cover at least 70% of the
vertebral surface that the engaging plate contacts. Member 104 may
separate engaging plate 102 from engaging plate 106. In certain
embodiments, member 104 may be held between engaging plates 102,
106 at least partially by pressure resulting from natural
compression of the spine.
[0066] Engaging plates 102, 106 may contact adjacent vertebrae to
anchor the disc implant to the spine. Coupling projections 108
positioned on outer surfaces 110, 110' of engaging plates 102, 106
may be positioned in a recess of a vertebral surface. Coupling
projections 108' positioned on outer surfaces 110, 110' of engaging
plates 102, 106 may penetrate into vertebral surfaces to inhibit
movement of the engaging plates relative to the vertebrae. In
certain embodiments, engaging plates may be coupled to vertebrae
using methods other than, or in addition to, coupling projections
108, 108'. For example, fasteners may be used to attach an engaging
plate to a vertebra. Fasteners may include, but are not limited to,
screws, nails, rivets, trocars, pins and barbs.
[0067] Inner surface 112 of engaging plate 102 may include slots
114 and recess 116. Slots 114 may have a cross-sectional shape
including, but not limited to, square, rectangular, trapezoidal, or
irregular. Inner surface 112' of engaging plate 106 may include
slots 114' that align with slots 114 of engaging plate 102 when
disc implant 100 is assembled. Slots 114, 114' may include indents
118. Indents 118 may engage an instrument used to facilitate
insertion of implant 100 during a surgical procedure. In some
embodiments, slots 114, 114' may be dovetailed. Slots 114, 114' may
allow use of insertion instruments without adding a height and/or a
thickness to the overall dimension of implant 100.
[0068] In some embodiments, slots in an engaging plate may be
parallel or substantially parallel to an anterior-posterior axis of
the engaging plates. FIG. 2 depicts an embodiment of engaging plate
106 wherein slots 114' are parallel to anterior-posterior axis 119.
In some embodiments, slots may be at acute angle relative to the
anterior-posterior axis of the engaging plate. FIG. 3 depicts an
embodiment of engaging plate 106 wherein slots 114' are angled
relative to anterior-posterior axis 119. Slots 114, 114' may be
formed at an angle ranging from about 15.degree. to about
30.degree. relative to anterior-posterior axis 119. In some
embodiments, slots 114, 114' may be formed at about a 25.degree.
angle relative to anterior-posterior axis 119. Angulation of slots
114, 114' may allow insertion of implant 100 using a modified
(e.g., angulated) anterior approach. In some embodiments, an
angular orientation of recess 116 may correspond to angulation of
slots 114, 114'. A modified anterior approach may facilitate
retraction of blood vessels above the L5 vertebrae. In some
embodiments, engaging plates 102, 106 with slots 114, 114' angled
relative to anterior-posterior axis 119 may not include a central
coupling projection (i.e., a keel).
[0069] Recess 116 of engaging plate 102 may have a cross-sectional
shape including, but not limited to, circular, elliptical, square,
rectangular or irregular. Sides of recess 116 may be tapered.
Posterior side 120 of recess 116 may be at least twice the height
of anterior side 122 of recess 116. A height difference between
anterior side 122 and posterior side 120 may minimize
overdistraction of the vertebrae required during positioning of
member 104 between engaging plates 102, 106 in a disc implant
procedure. In some embodiments, a bottom portion of the recess may
include an opening or openings to allow residual body fluids and/or
bone matter to be removed from the recess.
[0070] Base 124 of member 104 may fit in recess 116 of engaging
plate 102. Base 124 may substantially conform to the shape of
recess 116. In some embodiments, member 104 may be a tapered boss.
A width of base 124 that fits in recess 116 may be slightly less
than a width of the recess to allow member 104 to translate in the
recess. Recess 116 may maintain a position of member 104 between
engaging plates 102, 106.
[0071] Member 104 may include center section 126. A height of
center section 126 of member 104 may add thickness to a height of
implant 100. Center section 126 may range in height from about 5 mm
to about 20 mm. In certain embodiments, center section 126 may have
a height of about 9 mm. In some embodiments, center section 126 may
have a height of about 11 mm. In other embodiments, center section
126 may have a height of about 13 mm.
[0072] Center section 126 may include projections 128. Projections
128 may be an integral part of center section 126. In some
embodiments, projections 128 may be glued, press fit and/or welded
to center section 126. Projections 128 may be the same height as
center section 126. Projections 128 may engage an instrument to
facilitate insertion of member 104 between engaging plates 102,
106.
[0073] Member 104 may include convex portion 130. Convex portion
130 may be, but is not limited to being, an ellipsoidal section, an
ovate section or a spherical section. Inner surface 112' of
engaging plate 106 may include a recess. FIG. 2 depicts a bottom
view of inner surface 112' of engaging plate 106 shown in FIG. 1.
Recess 132 may complement convex portion 130 of member 104. In some
embodiments, a height of convex portion 130 may exceed a depth of
recess 132. As used herein, "complement" or "complementary" refers
to shapes of implant components that fit together to allow smooth
relative motion of the components.
[0074] FIG. 3 depicts a bottom view of inner surface 112' of an
embodiment of engaging plate 106 with slots 114' angled relative to
anterior-posterior axis 119. Slots 114' may be formed at an angle
ranging from about 15.degree. to about 30.degree. relative to
anterior-posterior axis 119. In some embodiments, slots 114' may be
formed at about a 25.degree. angle relative to anterior-posterior
axis 119. In certain embodiments, an orientation of recess 132 may
be angled to correspond to an angle of slots 114'. Angulation of
slots 114' may allow insertion of implant 100 using a modified
(e.g., angulated) anterior approach.
[0075] FIG. 4 depicts a cross-sectional view of the implant shown
in FIG. 1 after the implant has been assembled. Convex portion 130
of member 104 may complement recess 132 of engaging plate 106. A
shape of convex portion 130 may allow engaging plate 106 to move
(e.g., rock) in an anteroposterior plane and/or a mediolateral
plane relative to engaging plate 102. Movement of engaging plate
106 relative to engaging plate 102 in the anteroposterior plane
indicated by arrow 134 may allow flexion and extension of vertebrae
adjacent to the engaging plates. Movement of engaging plate 106
relative to engaging plate 102 in the mediolateral plane indicated
by arrow 136 in FIG. 1 may allow lateral bending of the vertebrae
adjacent to engaging plates 102, 106. Engaging plate 106 may rotate
relative to engaging plate 102 around axis of rotation 138 in the
plane indicated by arrow 140. In some embodiments, axial rotation
of engaging plate 106 relative to engaging plate 102 may be limited
by tissue, bone or other material in the patient.
[0076] In some embodiments, a height of convex portion 130 and a
depth of recess 132 may be chosen to limit lateral movement of
engaging plate 106 relative to engaging plate 102. For example, a
height of convex portion 130 may allow engaging plate 106 to
contact engaging plate 102 when engaging plate 106 rocks in the
direction of engaging plate 102. Contact of inner surfaces 112,
112' of engaging plates 102, 106 may provide a limit to
anteroposterior movement of engaging plate 106 relative to engaging
plate 102. Contact of inner surfaces 112, 112' of engaging plates
102, 106 may limit flexion and/or extension of the adjacent
vertebrae. A height of convex portion 130 may determine maximum
flexion and/or extension allowed by the implant. In some
embodiments, a maximum amount of flexion may be limited to a range
between about 0.5.degree. and about 20.degree.. In some
embodiments, maximum flexion allowed by the implant may be about
10.degree.. In other embodiments, maximum flexion allowed by the
implant may be about 15.degree.. In some embodiments, a maximum
amount of extension may be limited to a range between about
0.5.degree. and about 12.degree.. In some embodiments, maximum
extension allowed by the implant may be about 8.degree.. In other
embodiments, maximum extension allowed by the implant may be about
5.degree..
[0077] In some embodiments, components of an implant may include
surfaces that contact to limit a maximum amount of lateral bending.
In some embodiments, an implant may allow equal amounts of lateral
bending so that the patient can laterally bend the same amount to
the right or the left. In some embodiments, a maximum amount of
lateral bending to the left may be different than a maximum amount
of lateral bending to the right to accommodate specific needs of a
patient. In some embodiments, an implant may be designed to allow a
maximum amount of lateral bending within a range between
.+-.0.5.degree. to about .+-.15.degree.. In some embodiments, the
maximum amount of lateral bending may be about .+-.10.degree.. In
some embodiments, the maximum amount of lateral bending allowable
by an implant may be about .+-.5.degree..
[0078] In alternative embodiments, a concave portion of a member
may complement a convex portion of an engaging plate. As shown in
FIG. 5, convex portion 142 of engaging plate 106 may complement
recess 144 of member 104 to form an implant. A large contact area
between engaging plate 106 and member 104 may advantageously
distribute a compressive load applied to the implant over a
relatively large area.
[0079] FIG. 6 depicts a perspective view of components of an
implant embodiment. Implant 100 may allow a full range of
physiological movement of vertebrae adjacent to the implant. Inner
surface 112 of engaging plate 102 may include at least one
projection. Projection 146 may be coupled to engaging plate 102. In
some embodiments, projection 146 may be an integral part of
engaging plate 102. Projection 146 may have a shape that allows
engaging plate 102 to rotate freely relative to member 104. The
shape of projection 146 may be, but is not limited to being,
tapered, round or square. Member 104 may include recess 148 (shown
in FIG. 7). Recess 148 may complement projection 146. Recess 148
may have a slightly larger cross section than projection 146 to
allow engaging plate 102 to move relative to member 104. A size
and/or shape of recess 148 relative to projection 146 may determine
a range of rotation of member 104 relative to engaging plate
102.
[0080] As depicted in FIG. 7, recess 148 and projection 146 may
define axis of rotation 138. Friction between engaging plate 102
and member 104 may be low enough to allow rotation of the engaging
plate relative to the member. Engaging plate 102 may rotate
relative to member 104 as indicated by arrow 140. Rotation of
engaging plate 102 relative to member 104 may imitate axial
rotation of the spine. A large contact area between recess 148 of
member 104 and projection 146 of engaging plate 102 may distribute
a compressive load applied to implant 100 over a relatively large
surface area.
[0081] Member 104 may include convex portion 150. Inner surface
112' of engaging plate 106 may include recess 152. Recess 152 of
engaging plate 106 may complement convex portion 150 of member 104.
The shape of convex portion 150 may allow engaging plate 106 to
move (e.g., rock) relative to member 104. Movement of engaging
plate 106 relative to member 104 may allow lateral movement (e.g.,
lateral bending) of vertebrae adjacent to the engaging plates. In
an alternative embodiment, member 104 may include a recess
complementary to a convex part of engaging plate 106.
[0082] Convex portion 150 may have an arcuate cross-sectional shape
in an anteroposterior plane and/or in a mediolateral plane. An
arcuate shape of convex portion 150 in the anteroposterior plane
may allow engaging plate 106 to rock relative to engaging plate 102
in the directions indicated by arrows 134 in FIG. 7. Movement of
engaging plate 106 relative to engaging plate 102 in the
anteroposterior plane may allow flexion and extension of vertebrae
adjacent to the engaging plates. An arcuate shape of convex portion
150 in the mediolateral plane may allow engaging plate 106 to move
relative to engaging plate 102 in directions indicated by arrow 136
in FIG. 6. Movement of engaging plate 106 relative to engaging
plate 102 in the mediolateral plane may allow lateral bending of
vertebrae adjacent to the engaging plates.
[0083] FIG. 8 depicts a bottom view of inner surface 112' of
engaging plate 106 shown in FIG. 7. Engaging plate 106 may include
recess 152. A shape of recess 152 may complement convex portion 150
of member 104. Recess 152 may be concave with an arcuate
cross-sectional shape in an anteroposterior plane and/or in a
mediolateral plane. A shape of recess 152 may allow movement of
engaging plate 106 relative to member 104 in an anteroposterior
plane and/or in a mediolateral plane. Movement of engaging plate
106 relative to member 104 in an anteroposterior plane and/or in a
mediolateral plane may allow flexion, extension and/or lateral
bending of vertebrae adjacent to engaging plates 102, 106.
[0084] In some embodiments, engaging plate 106 may include limiter
154, as shown in FIG. 7. Limiter 154 may be positioned to contact
surface 156 of member 104. Contact of limiter 154 and surface 156
may limit posterior movement of engaging plate 106 relative to
engaging plate 102. Contact of limiter 154 and surface 156 may
therefore limit extension of vertebrae adjacent to engaging plates
102, 106. A height of limiter 154 relative to inner surface 112' of
engaging plate 106 and/or a height of surface 156 relative to inner
surface 112 of engaging plate 102 may be chosen to limit extension
of vertebrae adjacent the implant. Maximum extension allowed by
implant 100 may range from about 3.degree. to about 12.degree.. In
some embodiments, maximum extension allowed by implant 100 may be
about 8.degree.. In other embodiments, maximum extension allowed by
implant 100 may be about 5.degree..
[0085] In some embodiments, inner surface 112' of engaging plate
106 may contact surface 156 of member 104. Contact of inner surface
112' with surface 156 may limit anterior movement of engaging plate
106 relative to engaging plate 102. Contact of inner surface 112'
of engaging plate 106 with surface 156 of member 104 may limit
flexion of vertebrae adjacent engaging plates 102, 106. A height of
surface 156 relative to inner surface 112 of engaging plate 102 may
be chosen to limit flexion of vertebrae adjacent to engaging plates
102, 106. Maximum flexion allowed by implant 100 may range from
about 5.degree. to about 20.degree.. In some embodiments, maximum
flexion allowed by implant 100 may be about 10.degree.. In other
embodiments, maximum flexion allowed by implant 100 may be about
15.degree..
[0086] FIG. 9 depicts a perspective view of components of an
embodiment of an implant. Implant 100 may allow limited axial
rotation of vertebrae adjacent to engaging plates 102, 106.
Engaging plate 102 may include recess 158. Edges of recess 158 may
be arced. The arcs may share a common center point. Base 124 of
member 104 may fit in recess 158. A surface of base 124 may
substantially conform to an arced surface of recess 158. A width of
base 124 may be less than a width of recess 158 such that member
104 may be able to translate in recess 158 along curves defined by
the edges of the recess.
[0087] FIG. 10 depicts a cross-sectional view of the implant shown
in FIG. 9 after the implant has been assembled. Base 124 of member
104 may complement recess 158 of engaging plate 102. Axis of
rotation 138 may be at or near the centroid of engaging plates 102,
106 or offset from the engaging plates. Rotation of engaging plate
102 relative to engaging plate 106 may allow rotation of vertebrae
adjacent implant 100.
[0088] A shape of recess 158 may allow engaging plate 102 to rotate
axially relative to engaging plate 106 in the plane indicated by
arrow 140. Movement of base 124 in recess 158 may limit axial
rotation of the vertebrae adjacent to engaging plates 102, 106.
Maximum axial rotation allowed by implant 100 may range from about
.+-.0.1.degree. to about .+-.6.degree.. In some embodiments,
maximum axial rotation allowed by implant 100 may be about
.+-.3.degree.. In other embodiments, maximum axial rotation allowed
by implant 100 may be about .+-.1.degree..
[0089] Engaging plate 106 may include recess 152. Recess 152 may
complement convex portion 150 of member 104. In an alternative
embodiment, member 104 may include a recess complementary to a
convex portion of engaging plate 106. Convex portion 150 may have
an arcuate cross-sectional shape in an anteroposterior plane and/or
in a mediolateral plane. An arcuate shape of convex portion 150 in
an anteroposterior plane may allow engaging plate 106 to move
(e.g., rock) relative to member 104 in the directions indicated by
arrow 134. Movement of engaging plate 106 relative to member 104 in
the anteroposterior plane may allow flexion and/or extension of the
vertebrae adjacent to the engaging plates. An arcuate shape of
convex portion 150 in a mediolateral plane may allow engaging plate
106 to move (e.g., rock) relative to member 104 in the directions
indicated by arrows 136 in FIG. 9. Movement of engaging plate 106
relative to member 104 in the mediolateral plane may allow lateral
bending of the vertebrae adjacent to the engaging plates.
[0090] In some embodiments, inner surface 112' of engaging plate
106 (shown in FIG. 10) may contact surface 156 of member 104.
Contact of inner surface 112' with surface 156 may limit movement
of engaging plate 106 relative to engaging plate 102 in the
anteroposterior plane. Contact of inner surface 112' with surface
156 may limit flexion of the spine. In certain embodiments, a
height of a surface 156 relative to inner surface 112 may be chosen
to limit flexion of the spine. Maximum flexion allowed by implant
100 may range from about 5.degree. to about 20.degree.. In some
embodiments, maximum flexion allowed by implant 100 may be about
10.degree.. In other embodiments, maximum flexion allowed by
implant 100 may be about 15.degree..
[0091] In some embodiments, posterior movement of engaging plate
106 relative to engaging plate 102 may be limited. Engaging plate
106 may include limiter 154. During use, limiter 154 may contact
surface 156 to limit posterior movement of engaging plate 106
relative to engaging plate 102. Contact of limiter 154 with surface
156 may limit extension of the spine. A height of limiter 154
relative to inner surface 112' and/or a height of contact surface
156 relative to inner surface 112 may be chosen to limit extension
of the spine. Maximum extension allowed by implant 100 may range
from about 3.degree. to about 12.degree.. In some embodiments,
maximum extension allowed by implant 100 may be about 8.degree.. In
other embodiments, maximum extension allowed by implant 100 may be
about 5.degree..
[0092] In some embodiments, inner surface 112 of engaging plate 102
may have a convex portion. Engaging plate 102 of implant 100 shown
in FIG. 11 includes convex portion 160. Convex portion 160 may have
an arcuate cross-sectional shape in an anteroposterior plane and/or
in a mediolateral plane. Member 104 may include recess 162, as
shown in FIG. 12. Edges of recess 162 may be arced. The arcs may
share a common center point. Convex portion 160 may fit in recess
162 of member 104. Convex portion 160 of engaging plate 102 may
complement recess 162. A width of convex portion 160 may be less
than a width of recess 162. Engaging plate 102 may translate in
recess 162 along curves defined by edges of the recess.
[0093] FIG. 13 depicts a cross-sectional view of the implant shown
in FIG. 11 after the implant has been assembled. Recess 162 of
member 104 may complement convex portion 160 of engaging plate 102.
A shape of convex portion 160 may allow relative movement of
engaging plates 102, 106 in the plane indicated by arrow 140 about
axis of rotation 138. Axis of rotation 138 may be at or near the
centroid of implant 100 or offset from the centroid.
[0094] Maximum axial rotation allowed by implant 100 may range from
about .+-.0.1.degree. to about .+-.6.degree.. In some embodiments,
maximum axial rotation allowed by implant 100 may be about
.+-.3.degree.. In other embodiments, maximum axial rotation allowed
by implant 100 may be about .+-.1.degree.. Rotation of engaging
plate 102 relative to engaging plate 106 may be limited by a height
of convex portion 160 relative to a depth of recess 162. In some
embodiments, rotation of engaging plate 102 relative to engaging
plate 106 may be limited by a curvature of convex portion 160
and/or a curvature of recess 162.
[0095] Inner surface 112' of engaging plate 106 may include recess
152. Recess 152 may be complementary in shape to convex portion 150
of member 104. Convex portion 150 may complement recess 152. Convex
portion 150 may allow engaging plate 106 to move (e.g., rock)
relative to member 104. Movement of engaging plate 106 relative to
member 104 may allow lateral movement of the spine. In some
embodiments, member 104 may include a recess complementary to a
convex portion of engaging plate 106.
[0096] Convex portion 150 may have an arcuate cross-sectional shape
in an anteroposterior plane and/or in a mediolateral plane. An
arcuate shape of convex portion 150 in the anteroposterior plane
may allow engaging plate 106 to move relative to member 104 in the
directions indicated by arrow 134. Movement of engaging plate 106
relative to engaging plate 102 in the anteroposterior plane may
allow flexion and/or extension of the spine. The arcuate shape of
convex portion 150 in the mediolateral plane may allow engaging
plate 106 to move relative to member 104 in the directions
indicated by arrow 136 shown in FIG. 11. Movement of engaging plate
106 relative to member 104 in the mediolateral plane may allow
lateral bending of the spine.
[0097] Inner surface 112' of engaging plate 106 may contact surface
156 of member 104. Contact of inner surface 112' with surface 156
may limit anterior movement of engaging plate 106 relative to
engaging plate 102. Contact of inner surface 112' with surface 156
may therefore limit flexion of vertebrae adjacent to engaging
plates 102, 106. A thickness of an edge of member 104 may limit
flexion allowed by implant 100. Maximum flexion allowed by implant
100 may range from about 5.degree. to about 20.degree.. In some
embodiments, maximum flexion allowed by implant 100 may be about
10.degree.. In other embodiments, maximum flexion allowed by
implant 100 may be about 15.degree..
[0098] In certain embodiments, disc implant 100 may include two
engaging plates and two members as depicted in FIGS. 14 and 16.
FIGS. 15 and 17 are cross-sectional views of implants 100 shown in
FIGS. 14 and 16, respectively. Engaging plate 102 of implants 100
may have convex portion 164. Convex portion 164 may have an arcuate
cross-sectional shape along at least one axis. The arcuate
cross-sectional shape along one axis of convex portion 164 may
increase an area of contact between engaging plate 102 and member
104. Member 104 may include recess 166. Recess 166 may complement
convex portion 164. A shape of convex portion 164 may allow
anteroposterior translation of member 104 relative to engaging
plate 102. Translation of member 104 relative to engaging plate 102
may allow positioning of implant 100 during a spinal stabilization
procedure.
[0099] A thickness of engaging plate 102 proximate convex portion
164 may exceed a thickness of engaging plate 102 proximate edges
168, 168' such that inner surfaces 112, 112" are sloped relative to
an outer surface of the engaging plate. In some embodiments, a
slope of inner surface 112 may be different than a slope of inner
surface 112". In certain embodiments, a thickness of member 104
proximate recess 166 may exceed a thickness of the member at edges
170, 170' such that surfaces 172, 172' are sloped relative to
surface 156.
[0100] Inner surfaces 112, 112" and surfaces 172, 172' may be
sloped to allow movement (e.g., rocking) of engaging plate 102
relative to member 104 in a mediolateral plane. Movement of member
104 in the direction indicated by arrow 136 may allow lateral
bending of vertebrae adjacent to engaging plates 102, 106. Inner
surfaces 112, 112" and surfaces 172, 172' may be sloped such that
lateral movement of the spine in a mediolateral plane is
restricted. In some embodiments, a slope of surface 172 relative to
surface 156 may be different than a slope of surface 172' relative
to surface 156. In some embodiments, slopes of surfaces 172, 172'
may be opposite in sign to slopes of inner surfaces 112, 112".
Movement of engaging plate 102 relative to member 104 may allow
inner surfaces 112, 112" to contact surfaces 172, 172'. Contact of
inner surfaces 112, 112" and surfaces 172, 172' may distribute a
compressive load applied to implant 100 over a relatively large
surface area.
[0101] Member 104 may include projection 146. Projection 146 may be
coupled to member 104. In some embodiments, projection 146 may be
an integral part of member 104. A shape of projection 146 may be,
but is not limited to being, tapered, round or square. Member 174
may include recess 148, as depicted in FIGS. 15 and 17. Recess 148
may complement projection 146. Recess 148 may have a slightly
larger cross section than projection 146 to allow relative movement
of members 104, 174. In some embodiments, member 174 may rotate
relative to member 104 about axis of rotation 138 indicated by
arrow 140. As shown in FIG. 15, axis of rotation 138 may be near a
center of implant 100. In some embodiments, axis of rotation 138
may be located more off-center, as depicted in FIG. 17. A range of
rotation of member 174 relative to member 104 may be limited by a
size and/or shape of recess 148 relative to a size and/or shape of
projection 146.
[0102] Surface 176 of member 174 may contact surface 156 of member
104 when projection 146 fits in recess 148. A relatively large
contact area between member 104 and member 174 may distribute an
effective load applied to implant 100 while allowing rotation of
vertebrae adjacent to the implant. For example, projection 146
(shown in FIG. 14) has a flat surface that may increase a contact
area between projection 146 and recess 148. Reducing friction
between member 104 and member 174 may allow facile rotation of the
members relative to each other.
[0103] Member 174 may have convex portion 178. Convex portion 178
may have an arcuate cross-sectional shape in an anteroposterior
plane. Engaging plate 106 may include recess 180 (shown in FIG. 15
and FIG. 17). Recess 180 may be concave with an arcuate
cross-sectional shape in an anteroposterior plane. Recess 180 may
complement convex portion 178 of member 174. In some embodiments,
recess 180 may have a slightly larger cross section than convex
portion 178 to allow movement of engaging plate 106 relative to
member 174. Movement of engaging plate 106 relative to member 174
may allow for flexion and/or extension of vertebrae adjacent to the
engaging plates in the plane indicated by arrows 134 in FIGS. 15
and 17.
[0104] In some embodiments, anteroposterior and/or lateral movement
of components of implant 100 relative to each other may be limited.
As shown in FIGS. 14 and 15, engaging plate 106 may include limiter
154. Limiter 154 may be a projection extending from inner surface
112' of engaging plate 106. In an embodiment, limiter 154 may
extend along a side of engaging plate 106. Limiter 154 may be
positioned to contact surface 182 of member 174 when engaging plate
106 rocks in a posterior direction toward engaging plate 102.
Increasing a length of limiter 154 may increase an area of contact
between limiter 154 and member 174. Increasing the area of contact
between limiter 154 and member 174 may distribute a compressive
load on implant 100 over a relatively large area. Distributing the
load over a relatively large area may reduce stress among
components of implant 100.
[0105] Contact of limiter 154 with surface 182 may limit movement
of engaging plate 106 relative to member 174. A height of limiter
154 relative to inner surface 112' and/or a distance between
surfaces 176 and 182 of member 174 may be chosen to limit movement
of engaging plate 106 relative to member 174. In certain
embodiments, surface 182 of member 174 may be sloped relative to
surface 176 to increase an area of contact between surface 182 and
limiter 154. Surface 182 may be sloped to increase a range of
motion between engaging plate 106 and member 174. In some
embodiments, a slope of surface 182 may limit movement of engaging
plate 106 relative to member 174. In certain embodiments, maximum
extension allowed by implant 100 may range from about 3.degree. to
about 12.degree.. In some embodiments, maximum extension allowed by
implant 100 may be about 8.degree.. In other embodiments, maximum
extension allowed by implant 100 may be about 5.degree.. Some
implant embodiments may include a limiter designed to limit another
component of motion of a disc implant. Other implant embodiments
may include one or more additional limiters designed to limit other
components of motion of a disc implant.
[0106] In certain embodiments, inner surface 112' of engaging plate
106 may contact surface 182 of member 174. Contact of inner surface
112' with surface 182 may limit flexion of vertebrae adjacent to
engaging plates 102, 106. A distance between surfaces 176 and 182
of member 174 may be chosen to limit flexion between vertebrae
adjacent to engaging plates 102, 106. Maximum flexion allowed by
implant 100 may range from about 5.degree. to about 20.degree.. In
some embodiments, maximum flexion allowed by implant 100 may be
about 10.degree.. In other embodiments, maximum flexion allowed by
implant 100 may be about 15.degree..
[0107] In certain embodiments, components of implant 100 may be
coupled to one another. Coupling of components of implant 100 may
allow partial assembly of the implant prior to a surgical
procedure. In some embodiments, a manufacturer of implant 100 may
at least partially assemble the implant prior to shipment. Some of
the components of implant 100 may be held together during use, at
least partially, by pressure resulting from the natural compression
of the spine.
[0108] FIG. 18 depicts a perspective view of components of implant
100, including engaging plate 102, members 104 and 174, and
engaging plate 106. FIG. 19 depicts a cross-sectional view of the
implant shown in FIG. 18 after the implant has been assembled. As
shown in FIGS. 18 and 19, engaging plate 102 may include projection
146 and opening 184. Projection 146 may be coupled to engaging
plate 102. In some embodiments, projection 146 may be an integral
part of engaging plate 102. A shape of projection 146 may be, but
is not limited to being, round, square, rectangular or irregular.
Projection 146 may complement recess 148 (shown in FIG. 19) in
member 104. In certain embodiments, recess 148 may have a slightly
larger cross section than projection 146 to allow engaging plate
102 to move relative to member 104. In some embodiments, recess 148
may have a cross section substantially equal to a cross section of
projection 146 to inhibit rotation of engaging plate 102 relative
to member 104.
[0109] In some embodiments, opening 184 may extend through engaging
plate 102. In other embodiments, opening 184 may extend to a fixed
depth in engaging plate 102. Opening 184 may be designed (e.g.,
threaded) to receive a coupling device such as coupler 186. Coupler
186 may be, but is not limited to being, a screw, a bolt or a pinch
clamp. Coupler 186 may couple member 104 to engaging plate 102.
During use, coupler 186 may extend through at least a portion of
member 104 into opening 184 of engaging plate 102. A head of
coupler 186 may be recessed in opening 188 of member 104. Coupler
186 may allow engaging plate 102 to move relative to member 104. In
some embodiments, engaging plate 102 may rotate around axis of
rotation 138 relative to first member 104 in the plane indicated by
arrow 140 in FIG. 19. Relative movement of engaging plates 102, 106
may allow axial rotation of vertebrae adjacent to implant 100. Axis
of rotation 138 may be offset from a center of engaging plates 102,
106 to imitate a longitudinal axis of rotation of a spine.
[0110] As shown in FIG. 18, member 104 may have convex portion 164.
Convex portion 164 may have an arcuate cross-sectional shape along
at least one axis. Member 174 may include recess 166. Recess 166
may have an arcuate cross section along at least one axis. Recess
166 may complement convex portion 164 of member 104, as shown in
the side view of implant 100 in FIG. 20. In some embodiments, a
thickness of engaging plate 102 proximate member 104 may exceed a
thickness of the engaging plate at ends 168, 168' such that inner
surfaces 112, 112" slope toward an outer surface of the engaging
plate. In some embodiments, a slope of inner surface 112 may be
different than a slope of inner surface 112". A thickness of member
174 proximate recess 166 may exceed a thickness of the member at
ends 190, 190' such that surfaces 192, 192' of second member 174
slope away from engaging plate 102. In some embodiments, a slope of
surface 192 may be different than a slope of surface 192'. In some
embodiments, slopes of surfaces 192, 192' may be substantially the
same magnitude as slopes of inner surfaces 112, 112",
respectively.
[0111] Sloped surfaces 112, 112" may allow engaging plate 102 to
move (e.g., rock) relative to member 104 in a mediolateral plane.
Relative movement of engaging plates 102, 106 may allow lateral
bending of vertebrae adjacent to the engaging plates in the plane
indicated by arrow 136 in FIG. 18. Contact of surfaces 112, 112"
and 192, 192', respectively, may distribute a compressive load
applied to implant 100 over a relatively large area.
[0112] In some embodiments, member 174 may have convex portion 178.
Convex portion 178 may have an arcuate cross-sectional shape.
Engaging plate 106 may include recess 180. Recess 180 may be
concave with an arcuate cross-sectional shape. Recess 180 may
complement convex portion 178. Recess 180 may have a slightly
larger cross section than convex portion 178 to allow engaging
plate 106 to move (e.g., rock) toward engaging plate 102 as
indicated by arrow 134 in FIG. 19. Movement of engaging plate 106
relative to member 174 may allow flexion and/or extension of
vertebrae adjacent to engaging plates 102, 106.
[0113] Member 104 may include one or more stops 194 (shown in FIGS.
18 and 19). Stops 194 may be coupled to one or both ends of member
104. In some embodiments, stops 194 may be an integral part of
member 104. Stops 194 may restrict anteroposterior translation of
member 174 relative to member 104. Restriction of translation of
member 174 relative to member 104 may facilitate positioning of
implant 100 between vertebrae.
[0114] In certain embodiments, contact of stop 194 with inner
surface 112' of engaging plate 106 may limit extension of vertebrae
adjacent to implant 100. A height of stop 194 and/or a thickness of
engaging plate 106 may limit extension allowed by implant 100.
Maximum extension allowed by implant 100 may range from about
3.degree. to about 12.degree.. In some embodiments, maximum
extension allowed by implant 100 may be about 8.degree.. In other
embodiments, maximum extension allowed by implant 100 may be about
5.degree..
[0115] Surface 182 of member 174 may be sloped relative to surfaces
192, 192' of the member. Inner surface 112' of engaging plate 106
may be sloped relative to an outer surface of the engaging plate. A
slope of surface 182 and/or a slope of inner surface 112' may be
chosen to increase a contact area between surface 182 and limiter
154 of engaging plate 106. A slope of surface 182 may be chosen to
increase a range of motion between engaging plate 106 and member
174. In some embodiments, a shape and/or size of recess 180 may
limit motion of engaging plate 106 relative to another component of
the implant.
[0116] In certain embodiments, inner surface 112' of engaging plate
106 may contact surface 182 of member 174. Contact of inner surface
112' and surface 182 may limit flexion of the spine. A distance
between surface 182 and surfaces 192, 192' of member 174 may be
chosen to limit flexion between vertebrae adjacent to engaging
plates 102, 106. Maximum flexion allowed by implant 100 may be from
about 5.degree. to about 20.degree.. In some embodiments, maximum
flexion allowed by implant 100 may be about 10.degree.. In other
embodiments, maximum flexion allowed by implant 100 may be about
15.degree..
[0117] In some embodiments, a first engaging plate may be
substantially the same as a second engaging plate. Manufacturing
costs may be reduced for implants with substantially equivalent
engaging plates. FIG. 21 depicts a perspective view of implant 100
with substantially equivalent engaging plates 102. Member 104 may
separate engaging plates 102. In certain embodiments, member 104
may have a rounded shape including, but not limited to, ovoid,
spheroid and ellipsoid. Member 104 may be formed from metal (e.g.,
chrome) or ceramic. In certain embodiments, member 104 may be
highly polished to inhibit wear. Engaging plates 102 may include
concave portions 132. Concave portions 132 may complement member
104. A thickness of member 104 may exceed a cumulative depth of
concave portions 132.
[0118] FIG. 22 depicts a cross-sectional view of the implant shown
in FIG. 21 after the implant has been assembled. A separation of
engaging plates 102 by member 104 may allow the engaging plates to
"rock" relative to one another. Rocking of engaging plates 102
relative to one another in an anteroposterior plane may allow
flexion and/or extension in the plane indicated by arrows 134.
Rocking of engaging plates 102 relative to one another in a
mediolateral plane may allow lateral bending in the plane indicated
by arrows 136 in FIG. 21.
[0119] A shape of member 104 may provide a large contact area
between the surface of member 104 and concave portions 132. A shape
of member 104 may decrease wear and/or failure of implant 100.
Concave portions 132 with an oval shape may allow member 104 to
imitate the movement of a human spine around axis of rotation 138.
Engaging plates 102 may freely rotate relative to one another
around axis of rotation 138 in the plane indicated by arrow 140. In
some embodiments, a position of axis of rotation 138 may change as
member 104 translates in recesses 132. In an embodiment, a range of
motion (e.g., axial rotation) may be limited by the shape of member
104 and/or the shape of concave portion 132.
[0120] In an embodiment, an inner surface of engaging plates 102
proximate concave portions 132 may be elevated. An elevation of one
or more surfaces 196A-196D (shown in FIG. 21) may be chosen to
limit relative movement of engaging plates 102. One or more
surfaces 196A-196D may be sloped relative to outer surfaces of
engaging plates 102 as shown in FIGS. 21 and 22. Slopes of surfaces
196A-196D may increase a contact area between engaging plates 102.
Increasing a contact area between engaging plates 102 may inhibit
wear of the implant.
[0121] In certain embodiments, surfaces 196D may limit flexion of
vertebrae adjacent to the spinal implant. Surfaces 196B may limit
extension of vertebrae adjacent to implant 100. Surfaces 196A and
196C may limit lateral bending of vertebra adjacent to implant 100.
In some embodiments, axial rotation of engaging plates 102 relative
to each other may be limited.
[0122] In some embodiments, an implant may be curved to accommodate
radial curvature of vertebrae. Implants may be provided with
varying amounts of radial curvature. For example, disc implants may
be provided with large, medium and/or small radial curvatures. An
indication of an amount of radial curvature provided by an implant
may be etched or otherwise marked on the implant.
[0123] In some disc implant embodiments, engaging plates may be
sloped to establish a desired lordotic curvature of a spine.
Several different implant components with differing lordotic
curvatures may be available to a surgeon so that the surgeon can
form an implant with a desired lordotic angle. Lordotic indications
may be etched or otherwise marked (e.g., color coded) on the disc
implant to indicate the amount of lordosis that the implant will
provide. In an embodiment, a lumbar disc implant may have a
lordotic angle range of about 5.degree. to about 20.degree. (e.g.,
about 12.degree.).
[0124] An engaging plate may be designed to promote coupling of the
engaging plate to a vertebral surface. Coupling engaging plates of
an implant to adjacent vertebrae may stabilize the disc implant. An
engaging plate may include one or more coupling projections to
facilitate coupling of the engaging plate to a vertebra. A coupling
projection may extend from an outer surface of an engaging plate.
Coupling projections may be, but are not limited to being, press
fit, welded, glued or otherwise affixed to an engaging plate.
Alternatively, coupling projections may be formed as part of an
engaging plate. Any combination of coupling projections 108 may be
used together to ensure stability of implant 100.
[0125] An engaging plate may include one coupling projection 108,
as shown, for example, in FIGS. 9-11. FIG. 23 depicts a view of
engaging plate 102 with two coupling projections 108. In some
embodiments, an engaging plate may include a plurality of coupling
projections 108, as shown in FIGS. 24 and 25. In some embodiments,
an engaging plate may include coupling projections of substantially
the same shape and size. In certain embodiments, an engaging plate
may include coupling projections of different sizes and/or shapes.
A shape and/or size of a coupling projection may be chosen based on
factors including, but not limited to, durability, distribution of
load and ease of forming a complementary recess in a vertebra.
[0126] In certain embodiments, a coupling projection extending from
an engaging plate may be positioned in a recess formed in a
vertebra. The recess may complement the coupling projection.
Coupling projection 108 may have an arcuate cross section, as
depicted, for example, in FIGS. 9-11. In some embodiments, a
coupling projection may have a square or rectangular cross section.
FIG. 26 depicts a view of coupling projection 108 with a
rectangular cross section. In certain embodiments, a coupling
projection may be tapered in one or more directions. Coupling
projection 108 shown in FIG. 27 is tapered in an anteroposterior
direction. A tapered coupling projection may allow the coupling
projection to be wedged into a recess in a bone to secure the
engaging plate to the bone. Wedging the coupling projection in the
recess may inhibit movement of the engaging plate relative to the
vertebra and/or expulsion of the engaging plate from the bone. In
some embodiments, surfaces of the coupling projection that are to
be positioned adjacent to bone may be roughened or include a
coating (e.g., hydroxyapatite) to promote osseointegration of the
coupling projection with the bone. In some embodiments, coupling
projections, such as those depicted in FIGS. 1, 24 and 25, may
penetrate adjacent bone to inhibit movement of the engaging plate
relative to the vertebra and/or to inhibit expulsion of the
engaging plate from the bone.
[0127] In some embodiments, one or more coupling projections may be
oriented substantially in an anteroposterior plane to facilitate
implant insertion using an anterior approach. In some embodiments,
one or more coupling projections may be oriented substantially in a
mediolateral plane to facilitate implant insertion using a lateral
approach. In certain embodiments, combinations of coupling
projections of various cross-sectional shapes, such as those
depicted in FIG. 1 may be used to inhibit movement of the engaging
plate relative to the vertebra and/or expulsion of the engaging
plate from the bone.
[0128] In some embodiments, a fastening system may be used to
couple an implant to a vertebra. The implant may include a tab with
an opening in a face of the tab. The opening may engage or couple
to a head of a bone fastener. A fastening system may include a
fastener and a locking mechanism. The locking mechanism may be
positioned between the implant and the fastener. The locking
mechanism may inhibit backout of the fastener from the vertebra and
from the implant. In some embodiments, the locking mechanism may be
a ring positioned in an opening in the implant. When the ring is in
the opening, a head of the fastener inserted through the ring may
contact the ring if the fastener begins to back out of the opening.
The ring and fastener head combination may be too large to exit the
opening, thereby inhibiting backout of the fastener from the
vertebrae and from the implant. When the ring is positioned in the
opening, the ring may lock to the fastener head without locking to
the implant, thus allowing the plate to be securely tightened to
the vertebra. U.S. Pat. No. 6,454,769 to Wagner et al. and U.S.
Pat. No. 6,331,179 to Freid et al., both of which are incorporated
by reference as if fully set forth herein, describe fastening
systems including locking mechanism for inhibiting backout of
fasteners.
[0129] In certain embodiments, one or more instruments may be used
to insert and/or position a disc implant between adjacent vertebrae
after a discectomy has been performed. An inserter may be used to
position an implant in a prepared disc space between adjacent
vertebrae. The inserter may be sufficiently long to allow placement
of a distal end of the inserter in the disc space from above an
incision in a patient. Engaging plates of an implant may be coupled
to arms at the distal end of the inserter.
[0130] FIG. 28 depicts a perspective view of an embodiment of
inserter 210. Inserter 210 may include body 212 and arms 214. Body
212 may have opening 216. Opening 216 may be sized to allow one or
more guidance, insertion and/or removal instruments to be
positioned in inserter 210. Arms 214 may include extensions 218 for
coupling inserter 210 to engaging plates of an implant. Extensions
218 may be chamfered, rounded, dovetailed or otherwise machined to
engage slots 114 in engaging plates 102, 106 (shown in FIG. 1).
Extensions 218 may include detents 220. Detents 220 may be
positioned in indents 118 of engaging plates 102, 106 to couple
inserter 210 to an implant. FIG. 29 depicts extensions 218 coupled
to engaging plates 102, 106.
[0131] Portions of arms 214 may be angled relative to each other to
establish a tapering separation distance between the arms. The
angled portions of arms 214 may facilitate insertion of instruments
that establish a desired separation distance between engaging
plates 102, 106 attached to inserter 210.
[0132] Arms 214 may include mechanisms 222. FIG. 30 depicts a
perspective side-view of inserter 210 that shows mechanisms 222 on
arms 214. As depicted in FIG. 28, inserter 210 may include slots
224. Slots 224 may extend through arms 214 and extensions 218 from
the mechanism 222 to a portion of the inserter near detents 220.
Slots 224 may allow section 226 of inserter 210 to bend. Pressing
mechanisms 222 may move section 226 and allow disengagement of
detents 220 from indents located in engaging plates. When
mechanisms 222 are pressed, detents may be disengaged from indents
in engaging plates to separate inserter 210 from the engaging
plates. In some embodiments, arms 214 may include reinforcement
members 228 that stabilize portions of the inserter that are not
able to move when mechanisms 222 are pressed. Reinforcement members
228 may limit outward movement of sections 226.
[0133] A proximal end of inserter 210 may be formed to engage a
driving instrument or a guidance instrument, such as a slap hammer
or a pusher. Slots 230 in a proximal end of inserter 210 (shown in
FIG. 28) may be machined or otherwise designed to receive a
coupling device such as coupler 232 shown in FIG. 31. FIG. 31
depicts a perspective view of inserter 210 coupled to slap hammer
234. Coupler 232 may engage an attachment mount of a driving
instrument or a guidance instrument. Slap hammer 234 may include
attachment mount 236. Coupler 232 may couple attachment mount 236
to inserter 210.
[0134] During some implant insertion procedures, an intervertebral
space may be too small to allow insertion of implant components
coupled to an inserter without scarring the surfaces of adjacent
vertebrae. Shims may be placed adjacent to the vertebrae. Engaging
plates coupled to an inserter may be positioned next to the shims.
The inserter may be driven downwards to separate the vertebrae and
insert the engaging plates between the vertebrae. After insertion
of the engaging plates, the shims may be removed.
[0135] In some embodiments, a distractor may be used to separate
adjacent vertebrae and/or to separate engaging plates to allow
insertion of a member between the engaging plates. FIG. 32 depicts
a perspective view of an embodiment of a distractor. Distractor 238
may include body 240, arms 242 and attachment mount 244. Body 240
and arms 242 may include grooves 246. Grooves 246 may be slightly
larger in cross-section than projections 128 of member 104 (shown
in FIG. 1). Projections 128 of member 104 may fit in grooves 246 to
allow member 104 to be guided through body 240 and arms 242 to a
position between engaging plates.
[0136] In some embodiments, grooves 246 may be sized and/or shaped
to accept only a particular sized member of an implant. For
example, a member for a 13 mm implant will not fit in a distractor
that establishes a separation distance sized for an 11 mm implant.
In some embodiments, members and distractors may be color coded
substantially the same color. A surgeon may know to only put a
member into a distractor of substantially the same color.
[0137] In certain embodiments, arms 242 may include reinforcement
member 248. Reinforcement member 248 may inhibit movement of arms
242 during insertion of a member between engaging plates to form an
implant.
[0138] Slots 250 on attachment mount 244 may be machined to receive
a coupler. A coupler may couple distractor 238 to a drive
instrument, such as a slap hammer.
[0139] FIG. 33 depicts a perspective view of distractor 238
positioned in inserter 210. Arms 242 may separate arms 214 of
inserter 210. As arms 214 are separated by distractor 238, engaging
plates 102, 106 are separated. Slots in engaging plates 102, 106
and arms 242 may separate arms 214 such that the engaging plates
remain substantially parallel during the separation process.
Engaging plates 102, 106 may remain substantially parallel during
insertion of a member between the engaging plates. Separation of
arms 214 with distractor 238 may minimize or eliminate contact of
the distractor with engaging plates 102, 106. Minimizing or
eliminating contact of distractor 238 with engaging plates 102, 106
during distraction may inhibit undesired separation of the engaging
plates from the inserter 210.
[0140] FIG. 34 depicts a perspective view of an embodiment of a
pusher. Pusher 252 may include body 254 and attachment mount 256. A
width of a distal end of body 254 may be less than a width of a
proximal end of the body. Body 254 may include projections 258.
Projections 258 may fit in grooves 246 of distractor 238 (shown in
FIG. 32) to allow pusher 252 to be guided through body 240 and arms
242 of the distractor. In some embodiments, pushers may be color
coded to match to a particular size of distractor. In some
embodiments, projections 258 may be sized so that the pusher fits
in any size of distractor.
[0141] Pusher 252 may be used to move a member through distractor
238 to a desired position between engaging plates. FIG. 35 depicts
a side view of an embodiment of pusher 252 positioned in distractor
238 and inserter 210. When pusher 252 is positioned in inserter
210, the pusher may maintain a position of a member between
engaging plates 102, 106 and allow for removal of distractor 238
from the engaging plates.
[0142] During some implant insertion procedures, a channel or
channels may be formed in vertebrae. The channel or channels may
correspond to a coupling projection or coupling projections of
engaging plates. Instrument guides may be used to facilitate
formation of a channel or channels in vertebrae. In some
embodiments, two instrument guides may be coupled to an inserter.
The instrument guides may be inserted into a disc space. A
distractor may be introduced into the inserter to move the
instrument guides against vertebrae. Channels may be formed in the
vertebrae using instruments in combination with the instrument
guides.
[0143] FIG. 36 depicts a perspective view of instrument guide 260.
Instrument guide 260 may include slots 261, stops 262, and guide
piece 264. Slots 261 may allow instrument guide 260 to be coupled
to extensions of arms of an inserter. Stops 262 may limit an
insertion depth of instrument guide 260 between vertebrae. Stops
262 may have openings 266. Fasteners may be positioned through
openings 266 to secure instrument guide 260 to a vertebra during
formation of a channel or channels in the vertebra. The fasteners
may include, but are not limited to, screws, pins, barbs, or
trocars. A head of a fastener may be too large to pass through
opening 266.
[0144] Guide piece 264 may be used to place a cutting edge of an
instrument (e.g., chisel, drill, reamer) at a desired location
relative to a vertebra. The instrument may be passed through guide
piece opening 268. Guide piece opening may properly orient a
cutting portion of the instrument relative to a vertebra that the
instrument is to form a channel in. A portion of the instrument may
be positioned in groove 270 to guide the cutting edge of the
instrument during formation of a channel in the vertebra. As the
instrument travels along groove 270, bone matter may be removed
from the vertebral surface adjacent to instrument guide 260 to form
a groove in the vertebra. Bone matter may be removed to form an
opening of a length and/or depth similar to a cross-sectional shape
of a coupling projection on an engaging plate.
[0145] FIG. 37 depicts a perspective view of distractor 238, driver
272 and instrument guides 260 coupled to inserter 210. Driver 272
may position a shaft of fastener 274 through an opening in stop 262
so that the fastener couples instrument guide 260 to the
vertebra.
[0146] FIG. 38 depicts a top view of chisel 276. FIG. 38A depicts a
side view of chisel 276. Chisel 276 may include end member 278,
shaft 280 and handle 282. End member 278 may include a cutting edge
capable of penetrating bone. In some embodiments, shaft 280 may be
bent to accommodate an angle between a proximal portion of an
inserter and a channel guide positioned between vertebrae.
[0147] FIG. 39 depicts a perspective view of instrument guides 260,
distractor 238, and chisel 276 coupled to inserter 210. End member
278 of chisel 276 may be inserted through a guide piece opening in
guide piece 264 and positioned in groove 270 of instrument guide
260. Cutting edges of end member 278 may be forced into a vertebra.
Insertion depth of end member 278 into the vertebra may be
monitored using fluoroscopic imaging. In some embodiments, shaft
280 may be marked with a scale. When the end member of the chisel
first contacts the vertebra, a first reading of the scale relative
to a top of the inserter may be taken. As the chisel is driven into
the vertebra, an estimate of the insertion depth may be provided by
taking the difference between the current scale reading relative to
the top of the inserter and the first reading of the scale relative
to the top of the inserter. In some embodiments, a stop may be
positioned on shaft 280 to limit insertion depth of the chisel into
a vertebra. The stop may contact guide piece 264.
[0148] FIG. 40 depicts a perspective view of a reamer in
combination with inserter 210, distractor 238 and instrument guides
260. Reamer 284 may allow removal of bone matter from a vertebral
surface to form a groove in the vertebral surface. The groove may
have an arcuate cross-sectional shape to complement an arcuate
shaped coupling projection on an engaging plate (as shown in FIGS.
9-11). Reamer 284 may include cutter 286, body 288 and handle 290.
In some embodiments, a drive shaft may be positioned in body 288.
The drive shaft may be coupled to cutter 286 and to handle 290. The
drive shaft may be flexible or include flexible joints so that
cutter 286 will be oriented in a proper direction relative to the
inserter and the vertebra. Cutter 286 may be inserted in an opening
of guide piece 264 of instrument guide 260. Rotation of handle 290
may allow cutter 286 to remove vertebral bone and form a groove in
the vertebra. Contact of stop 292 with guide piece 264 may limit an
insertion depth of cutter 286 into the vertebra. A position of stop
292 along body 288 may be adjustable. In some embodiments,
insertion depth of cutter 286 into the vertebra may be monitored
during formation of the groove using fluoroscopic imaging.
[0149] In certain embodiments, a trial spacer may be used during
formation of a disc space between vertebrae. A trial spacer may be
used to determine when an appropriate sized disc space is formed
between vertebrae. The trial spacer may also determine a size of
trial endplates and/or engaging plates. FIG. 41 depicts embodiments
of trial spacers 294. A distal end of trial spacer 294 may be
similar in size (e.g., small, medium or large) to engaging plates
and/or trial endplates.
[0150] During some implant insertion procedures, trial endplates
may be used to determine the proper height and lordotic angle of
the implant to be inserted into the patient. Top surfaces of the
trial endplates may be smooth and/or polished so that the trial
endplates easily slide between vertebrae. FIG. 42 depicts a bottom
view of trial endplate 296. Trial endplate 296 may include slots
114 to engage extensions of arms of an inserter. Slots 114 may
include indents 118. Indents 118 may engage detents of an inserter
to securely couple the inserter to trial endplate 296.
[0151] Trial endplates 296 may vary in thickness. For example, a
thickness of trial endplate 296 at an edge near slots 114 may
exceed a thickness of the trial endplate at an edge opposite the
slots. Trial endplates 296 may have slopes ranging from about
2.degree. to about 22.degree. (e.g., about 3.degree., about
6.degree., about 9.degree., about 12.degree.). The combined angle
of a top trial endplate and a bottom trial endplate may determine
the lordotic angle that will be established by engaging plates of a
implant that correspond to the trial endplates. For example, if two
trial endplates with 3.degree. of slope are used, an implant formed
between the vertebrae may be formed with two engaging plates, each
engaging plate having 3.degree. of slope. The formed implant may
establish a 6.degree. lordotic angle between the vertebra. If the
top trial endplate has 3.degree. of slope and the bottom trial
endplate has 6.degree. of slope, an implant formed between the
vertebrae may be formed with a top engaging plate having a
3.degree. slope and a bottom engaging plate having a 6.degree.
slope. The formed implant may establish a 9.degree. lordotic angle
between the vertebrae.
[0152] An instrumentation kit for an implant insertion procedure
may include individual trial endplates that correspond in height
and slope to each engaging plate supplied in the instrumentation
kit. If more than two engaging plates of the same size and slope
are supplied in the instrumentation set, only two trial endplates
corresponding to that size and slope engaging plate are needed in
the instrumentation set. Having a trial endplate that corresponds
to each engaging plate allows a surgeon to insert trial endplates
that correspond to available engaging plates between the vertebrae.
The surgeon is able to test every combination of implant that can
be formed using the trial endplates supplied in the instrumentation
kit. The surgeon can test an exact model of the implant that is to
be formed in the disc space by choosing the appropriate trial
endplates and distractor.
[0153] When the trial endplates are coupled to an inserter and
positioned in the disc space, a distractor may be positioned in the
inserter to separate the trial endplates. If the distractor easily
slides into the inserter, a larger distractor may be tried. If the
distractor cannot be inserted into the inserter, a smaller
distractor may be tried. If some force is needed to insert the
distractor into the inserter, the distractor may be the appropriate
distractor. An appropriate distractor may overdistract vertebrae by
about 1.5 mm to about 2.0 mm. Overdistraction of vertebrae by about
1.5 mm to about 2.0 mm may extend ligaments proximate the vertebrae
sufficiently to allow for relative movement of components of a disc
implant once the implant has been inserted. A fluoroscopic image
may be obtained to determine if the trial endplates establish
desired lordosis and height between the vertebrae. If the lordosis
or height is not correct, other trial endplates and/or distractors
may be coupled to the inserter. The inserter may be positioned
between the vertebra until the trial endplates and distractor
establish a desired height and lordotic angle between the
vertebrae. Engaging plates that correspond to the trial endplates
and a member that will slide down the distractor may be obtained
from the instrumentation kit.
[0154] FIG. 43 depicts perspective view of a member seater. Member
seater 298 may facilitate seating of a member of an implant between
engaging plates. Member seater 298 may include arms 300, 300' and
handles 302, 302'. Arms 300, 300' may be pivotally coupled to
handles 302, 302'. Arm 300' may be positioned on a topside of
projection 128 of member 104 (depicted in FIG. 1). Arm 300' may
engage slots 114 of engaging plate 102 (depicted in FIG. 1).
Compression of handle 302 in the direction of handle 302' may allow
arm 300' to move toward arm 300. Movement of arm 300' toward arm
300 may allow member 104 to be securely positioned in recess 116 of
engaging plate 102. After seating member 104, member seater 298 may
be removed from the intervertebral space.
[0155] Engaging plates, members and/or trial endplates may be made
of one or more biocompatible materials including, but not limited
to, metals, alloys, ceramics, polymers and/or composites. For
example, an alloy may include cobalt-chrome-molybdenum (CoCrMo).
Ceramics may include, but are not limited to, alumina, zirconia or
composites. Polymers used for implant components may include
ultra-high molecular weight polyethylene, polyfluorocarbons and/or
polyesteresterketone (PEEK). In some embodiments, all components of
a disc implant may be formed of metal. In certain embodiments,
engaging plates and/or members may be formed of titanium, titanium
alloys, steel and/or steel alloys. In addition, materials may be
chosen based upon characteristics such as durability and ease with
which biological tissue, such as human bone, fuse with the
material. For example, titanium may wear poorly over time, but may
fuse well with bone. A cobalt-chrome-molybdenum alloy may wear
well, but may not fuse as well with biological tissue.
[0156] In some embodiments, engaging plates and/or members may be
or may include bioabsorbable material. Surfaces of engaging plates
and/or members that contact bone may include a coating to promote
osseointegration of the implant component with bone. The coating
may be, but is not limited to, a bone morphogenic protein,
hydroxyapatite and/or a titanium plasma spray.
[0157] In certain embodiments, engaging plates, members and/or
trial endplates of an implant may be formed of different materials
to decrease wear of the implant over time. An implant embodiment
may include engaging plates formed of titanium or
cobalt-chrome-molybdenum and one or more members formed of ceramic
(such as alumina) or polymer (such as ultra-high molecular weight
polyethylene). Material choice may be influenced by various
factors. For example, many polymers tend to "flow" when they are
produced at less than a certain thickness, possibly deforming and
leading to the failure of an implant. Ceramics, however, do not
tend to deform, but may potentially shatter under pressure.
[0158] In certain embodiments, an implant and/or trial endplates
may be distributed and/or sold pre-assembled and stored in sterile
packaging until needed. In some implant embodiments, radiological
markers may be placed in components of an implant that are
invisible to x-rays. The radiological markers may allow the
position of the component to be determined using x-rays or other
imaging techniques. The ability to determine the position of all
components of an implant may eliminate a need to have a surgical
procedure to determine the location of the implant.
[0159] In some embodiments, steps may be taken to adjust the
coefficient of friction of materials used to form engaging plates,
members and/or trial endplates. Implant components may be machined,
formed and/or chemically treated to decrease the coefficient of
friction and reduce the amount of wear on engaging plates and/or
members. In some implant embodiments, an insert, coating, liner or
other covering may be placed on all, or a portion, of a surface of
the engaging plates and/or members. The insert, coating, liner or
covering may modify frictional or other physical properties of an
engaging plate and/or member relative to another component of an
implant. In some embodiments, a surface of a member and/or an inner
surface of an engaging plate may include a surface coating to
reduce noise resulting from contact between implant components.
[0160] An implant may be positioned in an intervertebral space
between adjacent vertebrae using an anterior, lateral and/or
posterior approach. A surgeon may perform a discectomy to remove
all or a portion of an intervertebral disc. Instruments such as
curettes, rongeurs and bone shavers may be used to prepare the disc
space for the implant. Vertebral surfaces that will contact
engaging plates of an implant may be cleaned of cartilage or other
tissue. The vertebral surfaces may be shaped to substantially
conform to outer surfaces of engaging plates to be placed against
the vertebral surfaces.
[0161] In an implant insertion procedure, trial spacers may be
inserted in the intervertebral space to determine if a formed disc
space is sufficiently large and/or to determine a size of an
implant to be inserted in the disc space (e.g., small, medium or
large). Radiological images may be taken during the discectomy with
a trial spacer positioned between the vertebrae to determine if a
disc space of the proper width and depth has been formed. One or
more marks may be scored or burned into a surface of a vertebra
close to a center of an edge of the vertebra. The mark or marks may
be used as references to determine a proper lateral position of the
implant and/or instrumentation during insertion of the implant.
[0162] If needed, instrument guides may be positioned against
vertebrae. A reamer or a chisel may be used in conjunction with the
instrument guides to form recesses in the vertebrae. The recess may
have a shape that conforms to a shape of a coupling projection that
extends from an engaging plate of an implant to be positioned
between vertebrae.
[0163] Trial endplates may be coupled to an inserter. The trial
endplates may be positioned between the vertebrae. A distractor of
a determined height may be positioned in the inserter to separate
the trial endplates. During some insertion procedures, a mallet or
other impact device may be used to drive the distractor into the
inserter. If the trial endplates and distractor combination do not
establish a desired separation height and/or lordotic angle between
the vertebrae, different trial endplates and/or different
distractors may be tested until a combination of trial endplates
and distractor is found that establishes the desired separation
height and lordotic alignment of the vertebrae. If removal of trial
endplates from a disc space is difficult, a slap hammer or other
impact device may be used to facilitate removal of the inserter and
trial endplates from the disc space. Using various combinations of
trial endplates and distractors may allow a surgeon to determine
the correct lordotic angle and height of implant components to be
inserted in the intervertebral space.
[0164] Engaging plates that correspond to trial spacers that
establish a desired separation height and lordotic angle may be
chosen from available engaging plates supplied in an
instrumentation kit. The chosen engaging plates may be coupled to
arms of an inserter. The engaging plates may be positioned in the
disc space. The chosen distractor may be positioned in the
inserter. During some insertion procedures, a mallet or other
impact device may be used to drive the distractor into the
inserter. Positioning the distractor in the inserter may separate
engaging plates attached to the arms to a desired separation
distance. Separation of the engaging plates may force coupling
projections of the engaging plates into surfaces of adjacent
vertebrae to anchor the engaging plates to the bone.
[0165] A member that will slide down channels of the distractor may
be obtained from the instrumentation set. The member may be
positioned in the distractor and guided between engaging plates
with a pusher. The pusher may be coupled to the inserter to
maintain a position of the member between the engaging plates.
After the member is positioned between the engaging plates, a
mechanism on the arms of the inserter may be engaged to release the
extension on the arms from the engaging plates. The inserter,
distractor and pusher may be removed from the disc space. During
some insertion procedures, a slap hammer may be used to facilitate
removal of the inserter, distractorand/or pusher from the disc
space. Radiological images may be taken to ensure that the implant
is positioned as desired.
[0166] During some insertion procedures, a member seater may be
used after an inserter has been removed from the engaging plates.
The member seater may be positioned on a projection of a member and
in a slot of an engaging plate. Handles of the member seater may be
compressed to securely seat the member in a recess of the engaging
plate. The handles may be released to disengage the arms from the
projections and from the engaging plate. The member seater may be
removed from the intervertebral space.
[0167] In this patent, certain U.S. patents have been incorporated
by reference. The text of such U.S. patents, is, however, only
incorporated by reference to the extent that no conflict exists
between such text and the other statements and drawings set forth
herein. In the event of such conflict, then any such conflicting
text in such incorporated by reference U.S. patents is specifically
not incorporated by reference in this patent.
[0168] Further modifications and alternative embodiments of various
aspects of the invention will be apparent to those skilled in the
art in view of this description. Accordingly, this description is
to be construed as illustrative only and is for the purpose of
teaching those skilled in the art the general manner of carrying
out the invention. It is to be understood that the forms of the
invention shown and described herein are to be taken as examples of
embodiments. Elements and materials may be substituted for those
illustrated and described herein, parts and processes may be
reversed and certain features of the invention may be utilized
independently, all as would be apparent to one skilled in the art
after having the benefit of this description of the invention.
Changes may be made in the elements described herein without
departing from the spirit and scope of the invention as described
in the following claims.
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