U.S. patent application number 13/693847 was filed with the patent office on 2013-04-18 for transcorporeal spinal decompression and repair system.
The applicant listed for this patent is David Lowry, Desmond O'Farrell, Scott Tuinstra, Roger Veldman. Invention is credited to David Lowry, Desmond O'Farrell, Scott Tuinstra, Roger Veldman.
Application Number | 20130096628 13/693847 |
Document ID | / |
Family ID | 40020223 |
Filed Date | 2013-04-18 |
United States Patent
Application |
20130096628 |
Kind Code |
A1 |
Lowry; David ; et
al. |
April 18, 2013 |
TRANSCORPOREAL SPINAL DECOMPRESSION AND REPAIR SYSTEM
Abstract
A system and method are provided for making an access channel
through a vertebral body to access a site of neural compression,
decompressing it, and repairing the channel to restore vertebral
integrity. System elements include an implantable vertebral plate,
a guidance device for orienting bone cutting tools and controlling
the path of a cutting tool, a bone cutting tool to make a channel
in the vertebral body, a tool for opening or partially-resecting
the posterior longitudinal ligament of the spine, a tool for
retrieving a herniated disc, an implantable device with osteogenic
material to fill the access channel, and a retention device that
lockably-engages the bone plate to retain it in position after
insertion. System elements may be included in a surgery to
decompress an individual nerve root, the spinal cord, or the cauda
equina when compressed, for example, by any of a herniated disc, an
osteophyte, a thickened ligament arising from degenerative changes
within the spine, a hematoma, or a tumor.
Inventors: |
Lowry; David; (Holland,
MI) ; O'Farrell; Desmond; (Grand Rapids, MI) ;
Tuinstra; Scott; (Holland, MI) ; Veldman; Roger;
(Hudsonville, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lowry; David
O'Farrell; Desmond
Tuinstra; Scott
Veldman; Roger |
Holland
Grand Rapids
Holland
Hudsonville |
MI
MI
MI
MI |
US
US
US
US |
|
|
Family ID: |
40020223 |
Appl. No.: |
13/693847 |
Filed: |
December 4, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12210089 |
Sep 12, 2008 |
8323320 |
|
|
13693847 |
|
|
|
|
60972192 |
Sep 13, 2007 |
|
|
|
Current U.S.
Class: |
606/280 |
Current CPC
Class: |
A61B 17/1671 20130101;
A61B 17/809 20130101; A61B 17/686 20130101; A61B 17/7059 20130101;
A61B 17/1757 20130101; A61F 2002/4649 20130101; A61B 17/1637
20130101; A61B 17/70 20130101; A61B 2090/062 20160201 |
Class at
Publication: |
606/280 |
International
Class: |
A61B 17/16 20060101
A61B017/16 |
Claims
1. A surgical system to form an access channel through a vertebral
body, the channel having an anterior surface entry and a posterior
surface opening, the system comprising: a bone cutting tool with a
cutting element; and an integrated device comprising a bone plate
portion and trajectory control sleeve portion, the bone plate
portion configured to be secured to an anterior surface of the
vertebral body, the trajectory control sleeve portion having a
cylinder configured to receive at least a portion of the bone
cutting tool, the integrated device configured to guide the bone
cutting tool to form the access channel with a prescribed
trajectory from the anterior entry to the prescribed posterior
opening.
2. The surgical system of claim 1 wherein the bone plate portion
includes openings to accommodate fixation elements to secure the
bone plate portion to the anterior surface of the vertebral
body.
3. The surgical system of claim 1 wherein the trajectory control
sleeve portion is configured to direct the bone cutting tool on the
prescribed trajectory, the prescribed trajectory having an angle
according to a cranio-caudal axis and a medial lateral axis with
respect to a reference plane tangential to the access channel entry
on the anterior surface of the vertebral body.
4. The surgical system of claim 3 wherein the angle is a compound
angle.
5. The surgical system of claim 1 wherein the bone plate portion
provides a reference surface and wherein the trajectory control
sleeve portion may be configured with a range of angles formed with
respect to the surface of the bone plate portion on two axes, a
cranio-caudal axis and a medial lateral axis, the range of the
angles varying between about 1 degree and about 30 degrees from a
perpendicular angle.
6. The surgical system of claim 5 wherein the range of the angle
varies between about 10 degrees and about 30 degrees from the
perpendicular angle.
7. The surgical system of claim 1 wherein the trajectory control
sleeve portion includes a contact surface for engaging a
corresponding surface on the bone cutting tool, the surfaces
configured so as to limit the penetration of the cutting tool into
the vertebral body to a prescribed depth.
8. The surgical system of claim 1 wherein the posterior surface of
the bone plate portion includes one or more penetrating elements
configured to impinge into the vertebral bone tissue.
9. The surgical system of claim 1 wherein the bone plate portion
includes an anatomically-orienting feature to establish the
position of the bone plate portion relative to the medial
centerline of the vertebral body.
10. The surgical system of claim 1 wherein the bone-cutting tool is
any of a drill, a ream, a core cutter or a trephine.
11. The surgical system of claim 10 wherein the cutting element of
the bone-cutting tool has a cutting diameter between about 5 mm and
about 7 mm.
12. The surgical system of claim 1 further comprising an
implantable bone repair device having an external geometry
complementary to the internal geometry of the access channel.
13. The surgical system of claim 12 wherein the bone repair device
is sized to be insertable through an opening of the bone plate
portion, the opening being sized to receive the bone cutting
element.
14. The surgical system of claim 12 wherein the bone repair device
includes a bio-compatible material.
15. The surgical system of claim 12 wherein the bone repair device
includes a bio-absorbable material.
16. The surgical system of claim 12 wherein the bone repair device
includes an osteogenic agent.
17. The surgical system of claim 12 wherein bone repair device
includes receiving features in or on its anterior surface
configured to accommodate the attachment of an insertion tool.
18. The surgical system of claim 12 wherein the bone repair device
comprises a porous cage with a porosity sufficient to permit
through movement of blood and bone cells.
19. The surgical system of claim 18 wherein the composition of the
porous cage comprises any of a polymer, a metal, metallic alloy, or
a ceramic.
20. The surgical system of claim 19 wherein the polymer of the
composition may include polyetheretherketone (PEEK),
PEEK-reinforced carbon fiber, or hydroxyapatite-reinforced
PEEK.
21. The surgical system of claim 18 wherein the porous cage device
includes a closeable opening through which bone material may be
passed.
22. The surgical system of claim 18 wherein the porous cage device
includes a closeable cap configured to increase pressure within the
cage as the cap is closed.
23. The surgical system of claim 18 wherein the porous cage device
includes a minimally compressive internal element adapted to
enhance compressive force applied to contents of the porous cage
upon application of compressive force to the cage.
24. The surgical system of claim 1 further comprising a trajectory
and depth visualization device.
25. The surgical system of claim 24 wherein the trajectory and
depth visualization device includes a radio-opaque feature to allow
confirmation of the location of the bone plate portion device on
the appropriate vertebral body and to facilitate the extrapolation
of the projected trajectory of the bone cutting tool using a
radiographic image.
26. The surgical system of claim 24 wherein the trajectory and
depth visualization device includes visual markings to indicate a
distance from a point of contact with the vertebral body and cutter
penetration control feature on the bone cutter guide device.
27. A surgical system to form an access channel through a single
vertebral body overlaying a site in need of a medical procedure
adjacent a spinal cord in advance of performing the procedure
through the access channel, the channel having an anterior surface
entry and a posterior surface opening, the system comprising: an
integrated device comprising a bone plate portion and a trajectory
control sleeve portion; and a bone cutting tool, wherein the bone
plate portion of the integrated device comprises a curved surface
configured to contact an anterior surface of a single vertebral
body and to be temporarily secured to the anterior surface of the
vertebral body, wherein the trajectory control sleeve portion of
the integrated device comprises a cylinder configured to receive at
least a portion of the bone cutting tool, wherein the integrated
device and the bone cutting tool are configured to cooperate to
form a single access channel with a prescribed trajectory from an
anterior entry to a prescribed posterior opening on a posterior
surface of the vertebral body adjacent a spinal cord, the anterior
entry of the single access channel having a center that is
generally at a mid-point on a cranio-caudal length of the vertebral
body and generally offset from a medio-lateral mid-point of the
vertebral body, wherein the single access channel to be formed has
a circular cross-section along a single, straight axis from the
anterior entry in a posterior, caudal and lateral direction to the
prescribed posterior opening, the prescribed posterior opening
being located at or adjacent to the base of the posterior surface
of the single vertebral body, the single access channel having an
angle in the cranio-caudal direction of between about 1 degree and
about 30 degrees from perpendicular to the anterior surface at the
anterior entry, the single access channel having an angle in the
medio-lateral direction of between about 1 degree and about 30
degrees from perpendicular to the anterior surface at the anterior
entry, the single access channel having a diameter of between about
5 mm and about 8 mm, wherein a portion of the cutting tool is
configured to contact a portion of the integrated device to
precisely limit the penetration of the cutting tool into the
vertebral body to a prescribed depth.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 12/210,089 filed Sep. 12, 2008 which claims priority to U.S.
Provisional Patent Application No. 60/972,192 of Lowry et al.,
entitled "Transcorporeal spinal decompression and repair system and
related method", as filed on Sep. 13, 2007.
FIELD
[0002] The invention relates to devices and methods of spinal
surgery. More particularly, the invention provides an implant for
use in spinal repair surgery and a method for preparing the
vertebral volume to receive the implant.
INCORPORATION BY REFERENCE
[0003] All publications, patents and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent or patent
application was specifically and individually indicated to be
incorporated by reference.
[0004] In particular, U.S. patent application Ser. No. 11/855,124
of Lowry et al. (filed on Sep. 13, 2007, entitled " Implantable
bone plate system and related method for spinal repair"), U.S.
Provisional Patent Application 60/972,199 of Lowry et al. (filed on
Sep. 13, 2007, entitled "Device and method for tissue retraction in
spinal surgery") as well as the U.S. patent application Ser. No.
12/210,109, U.S. Provisional Patent Application No. 60/976,331 of
Lowry et al. (filed on Sep. 28, 2007, entitled "Vertebrally mounted
tissue retractor and method for use in spinal surgery"), and U.S.
Provisional Patent Application No. 60/990,587 of Lowry et al.
(filed on Nov. 27, 2007, entitled "Methods and systems for
repairing an intervertebral disk using a transcorporal approach")
are all incorporated by this reference.
BACKGROUND
[0005] The performance of cervical discectomy, excision of tissue,
and neural element decompression procedures have become standard
neurosurgical approaches for the treatment of disorders of the
spine and nervous system, as may be caused, for example, by disc
degeneration, osteophytes, or tumors. The compressive pathologies
impinge onto a neural element, causing a compression of nerve
tissue that results in a symptomatic response such as loss of
sensation or strength, occurrence of pain, or other related
disorders. The majority of these procedures are performed with an
anterior approach to the cervical spine. Disc and bone tissue are
removed, a neural decompression is achieved, and a spinal repair
procedure is performed.
[0006] The current conventional repair procedure includes a
vertebral fusion in which a biocompatible implant is inserted and
secured between the affected adjacent vertebrae. A bone plate is
then is rigidly attached to the two vertebrae adjacent to the
implant, immobilizing these vertebral segments and preventing the
expulsion of the implant from the intervertebral space.
Subsequently, osteogenesis of the vertebrae into the implant
occurs, and ultimately the adjacent vertebrae fuse into a single
bone mass. The fusion of the vertebral segments, however, can lead
to problematic results. For example, the immobility of the fused
vertebral joint is commonly associated with the progressive
degeneration of the adjacent segments, which, in turn, can lead to
degeneration of the intervertebral discs on either side of the
fused joint.
[0007] Implantation of an artificial disc device offers an
alternate approach to vertebral fusion. The objective of the
artificial disc device is to preserve the relative motion of the
vertebrae across the joint and to restore normal articulating
function to the spinal column. In spite of the benefits that these
procedures have brought to patients, both fusion and disc
replacement have inherent problems. The surgeries are extensive,
recovery time is relatively long, and there is often a loss of
function, particularly with the use of fusion implants. The
long-term biocompatibility, mechanical stability, and durability of
replacement disc devices have not been well established. Further,
there is no clinical consensus that the use of a replacement disc
reduces the risk of adjacent segment degeneration.
[0008] Methods for surgery on the spine and cervical discs from an
anterior approach were first developed in the 1950's, and a number
of variations have been developed since then. Each anterior
cervical discectomy procedure, however, has had to face the
challenge represented by removing the tissue overlaying the
compressing lesion (i.e., the herniated disc material, osteophyte
or tumor) after having dissected through the soft tissue anterior
to the spine. Early procedures exposed the compressing tissue by
first making a cylindrical bone-and-disc defect in the spine
centered on the disc space in sagittal and coronal planes, and
generally following the plane of the disc itself. Later procedures
made use of a rectangular, box-like defect in the disc space
centered on the disc space and generally following the plane of the
disc.
[0009] Procedures recently developed by Jho (referenced below) were
motivated by the concern that procedures like those described above
destroyed more of the natural disc tissue than was necessary to
remove a laterally-positioned disc herniation or osteophyte (a bone
spur). An alternative procedure, an uncovertebrectomy, was
therefore developed that involved the removal of only the
lateral-most aspect of the disc space, and the vertebral bone above
and below it, which together comprise the entire uncovertebral
joint. (See Choi et al., "Modified transcorporeal anterior cervical
microforaminotomy for cervical radiculopathy: a technical note and
early results", Eur. Spine J. 2007 Jan. 3; Hong et al., "Comparison
between transuncal approach and upper vertebral transcorporeal
approach for unilateral cervical radiculopathy--a preliminary
report", Minim Invasive Spine Surgery, 2006 October; 49
(5):296-301; and Jho et al., "Anterior microforaminotomy for
treatment of cervical radiculopathy: part 1: disc-preserving
functional cervical disc surgery", Neurosurgery 2002 November; 51
(5 Suppl.): S46-53.) This new type of procedure allows much of the
disc space to remain untouched. While preserving more of the disc
space and disc material than its predecessor procedures, the
uncovertebrectomy nevertheless does obliterate the uncovertebral
joint, and there is concern in the field regarding the eventual
development of spinal instability at that disc level. Further,
drilling bone at high speed adjacent to the nearby vertebral artery
and sympathetic nerve process increases the concern of a higher
risk of vertebral artery, secondary soft tissue injury, and Homer's
Syndrome.
[0010] In another refinement of the uncovertebrectomy procedure, an
anterior cervical microforamenotomy, the uncinate process and the
lateral disc tissue may be left largely intact as a hole is drilled
through the bone adjacent to the disc space near the uncinate
process. In both uncovertebrectomy and anterior microforamenotomy,
the exposure and decompression of the neural elements generally
follow the plane of the disc space. While vertebral artery injury
and spinal instability remain concerns with both procedures, the
risk associated with anterior microforamenotomy is considered less
than that of uncovertebrectomy.
[0011] An additional refinement of both uncovertebrectomy and
anterior microforamenotomy is a transcorporeal decompression
procedure (also referred to as an upper vertebral transcorporeal
foramenotomy or a transcorporeal discectomy) may have advantages.
This procedure differs from its disc space-preserving precedent
procedures in several ways. First, the axis of the access hole
drilled to expose the compressing pathology (e.g., herniated disc
fragment) does not parallel the plane of the disc, but instead
entirely avoids the disc space plane anteriorly and captures the
disc only at its most posterior aspect. Second, while
uncovertebrectomy and anterior cervical microforamenotomy are
applicable only to lateral pathology, the transcorporeal
decompression is potentially applicable to compressing pathology
located laterally in the disc space region, bilaterally, or in the
midline. Further, the procedure is performed from a substantially
medial position on the vertebra assuring maximal distance from the
vertebral artery and other sensitive soft tissue and thereby
minimizing the risk of accidental injury.
[0012] Multiple technical challenges remain, however, in optimizing
the transcorporeal cervical decompression procedure for general
surgical use. First, manually orienting and controlling a hand-held
cutting tool to make an access channel is a subjective and
error-prone procedure. The target pathology is wholly behind and/or
within the bony structure of the vertebra and is not visible in any
way when approached from a traditional anterior approach to the
cervical spine. As the channel is essentially being driven blindly,
it can easily fail to capture the targeted pathology being within
the range of the posterior opening of the access channel.
Consequently the surgeon needs to prolong the procedure, and
explore the space by excising tissue until the pathology is found.
The exploration typically leads to the access channel becoming
larger than necessary and undesirably irregular, thus putting
surrounding bone at risk of fracturing during or after the
procedure. Given the proximity of many target pathologies to the
uncovertebral joint and the vertebral artery, it is likely that
exploration of the space will lead to removal of the stabilizing
bone and disc tissue. This tissue damage or loss can cause spinal
instability, and may further result in accidental perforation of
the vertebral artery.
[0013] Second, a manual drilling process increases the risk of over
penetration into the spinal canal, with highly undesirable
consequences.
[0014] Third, the posterior longitudinal ligament, once exposed in
the access channel, can be difficult to open. The objective is to
remove the ligament cleanly from the access channel area so as to
provide unobstructed visualization of the compressed neural tissue.
Current surgical techniques are subjective and time-consuming,
often producing a shredding of the ligament within the access
channel rather than its removal therefrom, thereby impeding the
visualization of the underlying target pathology or dura mater
protective layer.
[0015] Fourth, currently available micro surgical instruments are
not well-suited for retrieving the herniated disc or bone fragments
that may be found deep to the posterior longitudinal ligament.
[0016] Fifth, after the decompression is complete, the present
solutions for filling the void remaining in the vertebra are not
completely satisfactory. Demineralized bone matrix putties or
similar materials can fill the defect but they offer no resistance
to the normal compressing or torsional forces until calcification
occurs. Such materials may also impose a new source of compression
on the exposed neural structures if too much putty is applied or if
the vertebra deforms or sustains a compression fracture
subsequently because of the absence of an implant that sufficiently
resists compressive forces.
[0017] Sixth, after a solid implant plug is placed in the
surgically-formed access channel, there is presently no anterior
cervical plate suited to preventing its outward migration.
Currently available anterior cervical plates are designed to be
placed across two or more adjacent vertebrae at or near the
midline, not laterally, as would be needed for lateral compressing
lesions. Existing plates also are designed as motion-restriction or
motion-prevention devices to be placed bridging across a disc space
rather than onto a single vertebral body, consequently they are too
large and are counterproductive in the application such as that
described above where the objective is to preserve the articulation
and relative motion of the adjacent vertebrae.
[0018] Accordingly, there is a need for a system and method whereby
any compressing spinal pathology may be removed or moved so as to
decompress the neural elements involved while desirably also (1)
preserving native disc and bone tissue and the natural motion of
the spine with natural disc material, (2) minimizing the risk of
injury to the vertebral artery, (3) minimizing the risk of
structural spinal instability, (4) minimizing the risk of an
inadequate decompression, (5) minimizing the risk of injury to the
protective dura mater layer, (6) minimizing the risk of post
operative bleeding and/or (7) minimizing the risk of a subsequent
vertebral body fracture due to an unrepaired defect within it.
SUMMARY OF THE DISCLOSURE
[0019] The invention provides a system and method for forming and
repairing an access channel through a vertebral body, typically a
cervical vertebral body, for the purpose of gaining access to a
site in need of a medical intervention. In its formation, the
channel originates on the anterior surface of the vertebral body,
and it then provides access from the anterior approach. The channel
follows a prescribed trajectory to a prescribed exit on the
posterior surface of the vertebral body, and provides an opening at
the site of sufficient size to address the medical need. The access
channel is typically formed in cervical vertebral bodies. The
nature of the medical need typically includes the need for a
decompression procedure, as may occur as a result of a problematic
portion or the whole of a herniated disc, an osteophyte, a
thickened ligament, a tumor, a hematoma, a degenerative cyst, or
any other compressing pathology. The medical intervention may be as
minimal as observing the site, or performing exploration, or it may
include a diagnostic procedure, or delivering a therapy, or it may
include a surgery. A typical surgery performed through the access
channel can include decompressing a neural element, such an
individual nerve root, a spinal cord, or a cauda equina.
[0020] The system of the invention further includes an implantable
bone repair device having an external geometry complementary to the
internal geometry of the access channel, and a method for repairing
or healing the channel by implanting such device. Some embodiments
of the device include materials that are biocompatible,
biologically absorbable, or any material known to be able to
substitute for bone, and to be able to be stably and effectively
integrated into bone. The device may further include as well as
biologically active agents, such as osteogenic agents, that promote
healing of the wound represented by the access channel, and fusion
of the device such that it integrates into the vertebral body.
[0021] In some embodiments, the implantable bone repair device
includes an assembly with a porous body that includes actual bone
tissue. Such bone tissue may be provided by the bone removed during
the formation of the channel itself, or it may come from another
site from the patient as an autologous graft, or it may be provided
by a separate donor.
[0022] The system to form and repair an access channel includes a
bone cutting tool with a cutting element, a bone plate configured
to be secured to the anterior surface of the vertebral body and
having an opening sized to receive the cutting element; and a
trajectory control sleeve configured to detachably engage the bone
plate and having a cylinder configured to receive the cutting
element. The bone plate and the trajectory control sleeve, when
mutually engaged, are configured to cooperate to guide the cutting
element to form the access channel with a prescribed trajectory
from the anterior entry to the prescribed posterior opening.
[0023] Embodiments of a method for prescribing of the point of
anterior entry and the channel trajectory toward the posterior
opening are typically provided by a physician who observes the
cervical spine of the patient radiographically. From such
observation of patient anatomy and the site of pathological
interest, the physician prescribes a trajectory according to a
cranio-caudal axis and a medial lateral axis with respect to a
point of entry on the anterior surface of vertebral body. Such
radiographic observation may occur before the attachment of the
bone plate, to be summarized below, and/or after the attachment of
the bone plate.
[0024] Returning to summarizing the system for forming the access
channel, some embodiments include fixation elements to secure the
bone to the anterior surface of the vertebral body. The bone plate
may include openings to accommodate fixation elements to secure the
bone plate to the anterior surface of the vertebral body. In some
embodiments, the bone plate and fixation elements are configured of
a biocompatible material. In some embodiments, the bone plate and
the fixation elements have a composition and structure of
sufficient strength that that the bone plate may be permanently
implanted.
[0025] Embodiments of the trajectory control sleeve may be
configured to direct the bone cutting tool on a trajectory
prescribed by the method above, the prescribed trajectory being an
angle according to a cranio-caudal axis and a medial lateral axis
with respect to a reference plane tangential to the access channel
entry on the anterior surface of vertebral body.
[0026] Embodiments of the bone plate provide a reference plane such
that the trajectory control sleeve, when secured to the bone plate,
may be configured with a range of angles formed on two axes with
respect to the plane of the bone plate, a cranio-caudal axis and a
medial lateral axis, the range of the angles varying between about
1 degree and about 30 degrees from an angle perpendicular to the
plate. In typical embodiments, the range of the angles varies
between about 10 degrees and about 30 degrees from the
perpendicular angle. In some embodiments, the system includes a
plurality of trajectory control sleeves, the sleeves varying in
regard to angles formed with respect to a plane represented by the
bone plate when secured thereto, the angles ranging between about
10 degrees and about 30 degrees cranio-caudally from a
perpendicular angle.
[0027] In some embodiments, the trajectory control sleeve and the
bone plate have mutually-engageable features that orient the
engagement of the trajectory control sleeve on the bone plate in a
configuration that allows the trajectory control sleeve to guide
the cutting tool into the vertebral body with the prescribed
trajectory. And in some embodiments, the trajectory control sleeve
includes a contact surface for engaging a corresponding surface on
the bone cutting tool, the surfaces configured so as to limit the
penetration of the cutting tool into the vertebral body to a
prescribed depth.
[0028] In some embodiments, the posterior surface of the bone plate
includes one or more penetrating elements configured to impinge
into the vertebral bone tissue to improve fixation and resist the
torsional forces associated with bone cutting procedures. In some
embodiments, the bone plate includes an anatomically-orienting
feature to establish the position of the bone plate relative to the
medial centerline of the vertebral body. In some embodiments, the
bone plate includes a biocompatible material. And in some
embodiments, at least a posterior surface of the bone plate is of
sufficiently porous composition to support in-growth of bone.
[0029] In various embodiments, the bone-cutting tool is any of a
drill, a reamer, a burr, or cylindrical cutting tool, such as a
core cutter or a trephine. In some of these embodiments, the
cutting element of the bone-cutting tool has a cutting diameter of
between about 5 mm and about 7 mm.
[0030] As noted above, embodiments of the implantable bone repair
device have an external geometry complementary to the internal
geometry of the access channel. These bone repair device
embodiments may be sized to be insertable through an opening of the
bone plate, the opening also being sized to receive the bone
cutting element. In some embodiments, the bone repair device
includes an abutting surface configured to engage a corresponding
surface of the bone plate through which it is implanted, the
engagement of these surfaces adapted to prevent the bone repair
device from penetrating too deeply into or through the access
channel of the vertebral body. In some embodiments, the bone repair
device includes receiving features in or on its anterior surface
configured to accommodate the attachment of an insertion tool.
[0031] In some of these embodiments, bone repair device and the
bone plate have mutually engageable orientation and locking
features. In various embodiments, the locking engagement results
from the application of an axial force to snap the locking feature
into a corresponding retaining feature of the bone plate. In other
embodiments, the locking engagement results from the application of
a torsional force to engage the locking feature into a
corresponding retaining feature in or on the bone plate.
[0032] In some embodiments of the surgical system the bone repair
device comprises a porous cage with a porosity sufficient to permit
through movement of biological fluids, such as blood, and bone
cells. The composition of the porous cage portion of the device may
include any of a polymer, a metal, a metallic alloy, or a ceramic.
An exemplary polymer may polyetheretherketone (PEEK), which may be
present in the form of PEEK-reinforced carbon fiber, or
hydroxyapatite-reinforced PEEK. In some embodiments of the bone
repair device with a porous cage, the porous cage device includes a
closeable opening through which harvested bone material (such a
native bone from the access channel site) may be passed. And in
some of these embodiments, the porous cage device includes a
closeable cap configured to increase pressure on the harvested bone
within the cage as the cap is closed. Further, some embodiments
include an internal element adapted to enhance compressive force
applied to the contents of the porous cage upon application of
compressive force to the cage, such force inducing extrusion of
harvested bone and blood from within the cage through its porous
structure to the external surfaces of the cage.
[0033] Some embodiments of the surgical system include a trajectory
and depth visualization device. In some of these embodiments, the
trajectory and depth visualization device includes a
radio-reflective feature so as to confirm the location of the bone
plate device on the appropriate vertebral body and to facilitate
the extrapolation of the projected trajectory of the bone cutting
tool using a radiographic image. In some embodiments, the
trajectory and depth visualization device includes visual markings
to indicate the distance from the point of contact with the
vertebral body and cutter penetration control feature on the bone
cutter guide device.
[0034] A method for performing a procedure through a vertebral body
overlaying a site in need of a medical procedure includes attaching
the bone plate on the anterior surface of the vertebral body,
engaging the trajectory control sleeve to the bone plate, inserting
a bone cutting tool through the trajectory control sleeve, and
forming an access channel body by removing bone with the bone
cutting tool (the channel having a centerline co-incident with the
centerline of the trajectory control sleeve through the vertebral),
disengaging the trajectory control sleeve from the bone plate, and
performing the medical procedure through the open space provided by
the access channel and the opening on the posterior surface of the
vertebral body.
[0035] The access channel follows a prescribed trajectory from an
anterior entry point to a prescribed opening on a posterior surface
of the vertebral body in the locale of the site in need of the
medical procedure. The prescription for the points of entry and
exit and the vectors of the access channel are determined by
radiographic observations and measurements, as summarized above. In
some embodiments of the method, forming the access channel includes
forming the channel with a constant, circular cross-section along a
single, straight axis aligned with the trajectory control
sleeve.
[0036] Before engaging the trajectory control sleeve to the bone
plate, the method may include selecting the sleeve to be used in
the procedure such that when the sleeve and the bone plate are
engaged, the sleeve has an angular orientation relative to the bone
plate that is consistent with the prescribed trajectory of the
access channel. Further, before attaching the bone plate to an
anterior vertebral surface, the method may include exposing one or
more vertebral bodies in a spinal column by anterior incision.
Further still, after performing the medical procedure, the method
may include leaving the bone plate attached to the vertebral
body.
[0037] In some embodiments of the method, after engaging the
trajectory control sleeve to the bone plate, the method may include
inserting a radiopaque locating device into the trajectory control
sleeve device, radiographically observing the locating device and
determining therefrom an extrapolated trajectory of the access
channel toward the posterior surface of the vertebral body, and
verifying that the extrapolated trajectory is consistent with the
prescribed trajectory such that the point of exit at the posterior
surface is proximal to the targeted site of interest.
[0038] In some embodiments of the method, after engaging the
trajectory control sleeve to the bone plate, the method may include
inserting a depth-measuring device into the trajectory control
sleeve device to establish an optimal depth of penetration of the
bone-cutting tool into the vertebral body, the depth being
influenced by the disposition of the bone plate against a variable
topography of the anterior surface of the vertebral body.
[0039] In some embodiments, after the completing the medical
procedure through the access channel, the method further includes
repairing the access channel with an implantable bone repair
device, the device having an external geometry complementary to the
internal geometry of the channel. In typical embodiment of the
method, repairing the access channel includes implanting the bone
repair device through the bone plate and into the channel. And in
some of these embodiments, the method includes securing a proximal
portion of the bone repair device to the bone plate.
[0040] In some embodiments of the method, repairing the access
channel includes in-growing bone from the vertebral body into at
least a portion of the surface of the bone repair device. And in
some embodiments, repairing the access channel includes stimulating
bone growth within the bone repair device by providing an
osteogenic agent within the repair device.
[0041] In some embodiments of the method, repairing the access
channel includes placing a portion of harvested native bone tissue
within a bone repair device that comprises a porous cage. In these
embodiments, the method may further include allowing or promoting
intimate contact between the bone tissue within the bone repair
device and bone tissue of the vertebral body. The method may
further include perfusing at least some bone tissue or
bone-associated biological fluid from the bone repair device into
the vertebral body. Still further, the method may include healing
together the harvested native bone tissue within the bone repair
device and bone tissue of the vertebral body.
[0042] In some embodiments of the system, the bone plate and the
trajectory control sleeve are an integrated or integrally-formed
device. In this embodiment, thus the system includes a bone cutting
tool with a cutting element and an integrated device comprising a
bone plate portion and trajectory control sleeve portion. The bone
plate portion is configured to be secured to an anterior surface of
the vertebral body and has an opening sized to receive the cutting
element. The trajectory control sleeve portion has a cylinder
configured to receive the cutting element of the bone cutting tool,
and the integrated device is configured to guide the bone cutting
tool to form the access channel with a prescribed trajectory from
the anterior entry to the prescribed posterior opening.
[0043] A method for performing a procedure through a vertebral body
overlaying a site in need of a medical procedure with the
integrated device summarized above includes attaching the
integrated device on an anterior surface of the vertebral body,
inserting a bone cutting tool through the trajectory control sleeve
portion of the device, forming an access channel through the
vertebral body by removing bone with the bone cutting tool, the
access channel prescribed as summarized above, disengaging the
integrated device from the bone plate, and performing the medical
procedure through the access channel and the opening on the
posterior surface of the vertebral body.
[0044] In some embodiments of the system and method, the bone plate
or integrally formed bone plate portion does not lie directly over
the anterior entry location for the access channel. Rather, the
bone plate or bone plate portion is attached to the anterior
surface of the vertebral body adjacent to the entry location, and
supports a trajectory control sleeve or sleeve portion which may be
located adjacent to the entry location.
BRIEF DESCRIPTION OF THE FIGURES
[0045] FIG. 1 is a view of an implantable bone plate device viewed
from an anterior perspective.
[0046] FIG. 2 is a view of an implantable bone plate device viewed
from a posterior perspective.
[0047] FIGS. 3A and 3B provide views of a trajectory control sleeve
attachment. FIG. 3A shows a trajectory control sleeve in a side
view.
[0048] FIG. 3B provides a side cross-sectional view of the
trajectory control sleeve, showing how the angle of the sleeve
relative to its base forms an asymmetrical opening in the base.
[0049] FIG. 3C shows the trajectory control sleeve from a
proximally-directed perspective.
[0050] FIG. 4 is an anterior perspective of the trajectory control
sleeve mounted to an implantable bone plate.
[0051] FIG. 5 is a lateral view of the trajectory control sleeve
mounted to an implantable bone plate.
[0052] FIG. 6 is a perspective view showing an implanted bone plate
screwed a vertebral body and with a trajectory control sleeve
mounted thereon.
[0053] FIG. 7 is an anterior view showing an implanted bone plate
screwed to a vertebral body and a trajectory control sleeve mounted
thereon.
[0054] FIG. 8 is a lateral view showing an implanted bone plate
screwed to a vertebral body and with a trajectory control sleeve
mounted thereon.
[0055] FIGS. 9A-9B show various views of a trajectory pin and a
drill depth gauge. FIG. 9A is a perspective view of a trajectory
pin and a drill depth gauge assembled together
[0056] FIG. 9B is a perspective view of an embodiment of the depth
gauge sub-assembly.
[0057] FIG. 10 is a lateral view of the trajectory pin assembly
shown in FIG. 9A engaged in a trajectory control sleeve.
[0058] FIG. 11 is a cross sectional view showing a trajectory pin
in full engagement with vertebral bone and a trajectory control
sleeve.
[0059] FIG. 12 is an anterior perspective view of a trajectory pin
and depth gauge engaged within a trajectory control sleeve.
[0060] FIG. 13 is a cross section view showing a bone drill in
position relative to a bone plate and trajectory control sleeve
prior to cutting bone tissue.
[0061] FIG. 14 is a perspective view of a bone plate after drilling
has been completed and the trajectory control sleeve has been
disengaged from the implanted bone plate.
[0062] FIG. 15 is a perspective view of a spinal repair implant in
the pre-insertion position relative to the implanted bone
plate.
[0063] FIG. 16 is a perspective view of a spinal repair implant
installed into an access channel through an implanted bone
plate.
[0064] FIG. 17 is an anterior perspective view of an alternate
embodiment of an implantable bone plate.
[0065] FIGS. 18A and 18B are views of the trajectory control sleeve
mounted on the bone plate embodiment of FIG. 17. FIG. 18A shows the
trajectory control sleeve and bone plate from distally directed
perspective.
[0066] FIG. 18B shows the trajectory control sleeve and bone plate
from a side view.
[0067] FIG. 19 shows an implantable bone plate in situ on a
vertebral surface.
[0068] FIG. 20 shows a perspective view of an implantable bone
plate and trajectory control sleeve in situ on the vertebra
surface.
[0069] FIG. 21 shows a drill cutter engaging vertebral bone tissue
through the trajectory control sleeve.
[0070] FIG. 22 shows an access channel through an implanted bone
plate and into vertebral bone tissue.
[0071] FIGS. 23 and 24 show an intra-vertebral repair device
engaging vertebral bone through the bone plate. FIG. 23 shows the
repair device being held by a surgeon immediately prior to
inserting into the access channel.
[0072] FIG. 24 shows the surgeon's finger pressing the repair
device through the bone plate and into the access channel.
[0073] FIGS. 25A and 25B show views of an intravertebral repair
device embodiment with a proximal abutting surface orthogonal to
the body of the device. FIG. 25A shows the device from a
proximally-directed perspective.
[0074] FIG. 25B shows the device of FIG. 25A from a
distally-directed perspective.
[0075] FIGS. 26A and 26B show views of an intravertebral repair
device embodiment with a proximal abutting surface canted with
respect to main axis of the body of the device. FIG. 26A shows the
device from a side view.
[0076] FIG. 26B shows the device of FIG. 26A from a
proximally-directed perspective.
[0077] FIGS. 27A and 27B show views of an intravertebral repair
device embodiment with a convex external profile, wider in its
central portion, narrower at proximal and distal ends. FIG. 27A
shows the device from a proximally-directed perspective.
[0078] FIG. 27B shows the device of FIG. 27A from a
distally-directed perspective.
[0079] FIG. 28 shows the primary components of an exemplary system
associated with the creation and repair of the intra-vertebral
access channel.
[0080] FIG. 29 shows a typical access channel that may be produced
with the inventive systems and methods.
[0081] FIG. 30 shows a cross sectional view of an access channel
being formed in a vertebral body with a hollow cutting tool, a
trephine, which forms an access channel with a removal bone
plug.
[0082] FIG. 31 shows an exploded view of a bone repair device with
a porous body configured to hold bone tissue, and to allow
compression of the tissue upon closing the porous body.
[0083] FIG. 32 shows a cut away cross sectional view of the bone
repair device of FIG. 31 in assembled form.
[0084] FIG. 33 shows an external view of the assembled bone repair
device of FIG. 33 with bone tissue and associated fluid being
extruded under pressure.
[0085] FIG. 34 shows an alternative embodiment of an assembled bone
repair device with a porous body and with an internal
pressure-amplifying feature.
[0086] FIG. 35 shows a bone repair device with a porous body
containing bone tissue poised in a position from where it is about
to be implanted in an access channel within a vertebral body.
[0087] FIG. 36 shows the bone repair device of FIG. 35 implanted in
the vertebral body, and locked into a bone plate.
[0088] FIG. 37 shows a lateral cross sectional view of a bone
repair device with a porous body containing bone tissue, in situ,
within an access channel in a host vertebral body.
DETAILED DESCRIPTION
[0089] An inventive surgical system and associated method of use
are provided for transcorporeal spinal procedures that create and
use an anterior approach to an area in need of surgical
intervention, particularly areas at or near a site of neural
decompression. Removal or movement of a source of compressing
neural pathology is achieved via a surgical access channel created
through a single vertebral body instead of through a disc space or
through an uncovertebral joint (involving 1 or 2 vertebrae). The
access channel has a specifically prescribed trajectory and
geometry that places the channel aperture at the posterior aspect
of the vertebra in at or immediately adjacent to the targeted
compressing pathology, thus allowing the compressing neural
pathology to be accessed, and removed or manipulated. The access
channel is formed with precise control of its depth and perimeter,
and with dimensions and a surface contouring adapted to receive
surgical instruments and an implanted bone repair device.
[0090] The channel may be used to access and operate on the
compressing pathology, more particularly to remove or to move a
portion or the whole of a herniated disc, an osteophyte, a
thickened ligament, a tumor, a hematoma, a degenerative cyst, or
any other compressing pathology. As a part of the procedure, the
posterior longitudinal ligament posterior to the transcorporeal
access channel may be opened or removed through the access channel,
thereby permitting the visualization or removal of any compressing
pathology otherwise obscured by the ligament.
[0091] The invention preserves native bone and disc tissue that is
sacrificed by prior art procedures, and further preserves the
natural motion of the vertebral joint. The procedure also preserves
at least the anterior half of the vertebral endplate of the
vertebral body upon which the cutting occurs. Removal or the
movement of the compressing pathology can proceed even when a
portion of the compressing pathology resides beyond the limits of
the transcorporeal access channel. Further, removal of the
compressing pathology may occur without inducing posterior or
inward compression on the dura mater protective layer surrounding
the spinal cord and exiting nerve roots, or exerting direct
pressure on the spinal cord or exiting nerve roots. Also, the
compressing pathology removal may occur without lacerating the dura
mater protective layer surrounding the spinal cord and exiting
nerve roots.
[0092] Embodiments of the system and method also pertain to
therapeutic occupation and repair of the vertebral body void
created by making such an access channel. This repair is achieved
by inserting an implantable vertebral repair device that has a
conformation complimentary to the internal geometry of the access
channel after the procedure is complete, and by securing the
implant in the inserted position by means of a vertebral bone
plate. The external surface of the vertebral repair device is in
substantial contact with the internal surface of the access channel
after insertion is complete, thereby substantially restoring
structural and mechanical properties of the vertebrae. Such repair
occurs without directly or indirectly inducing compression of
underlying dura mater or neural structures. The repair further
occurs without the subsequent anterior migration of the vertebral
repair device, which could cause injury to soft tissue structures
located anterior to the spine.
[0093] In some embodiments, the implanted device has a
bioabsorbable composition that allows replacement of the implant
device by in-growth of native bone tissue, or which is incorporated
into the native bone tissue. As a whole the system increases the
objectivity of considerations associated with spinal surgery,
reduces patient risk, and contributes to better and more
predictable surgical outcomes.
[0094] Various aspects and features of the invention will now be
described in the context of specific examples and with the
illustrations provided by FIGS. 1-37.
[0095] A number of tools and instruments are included in or used
within the system and methods described herein. FIG. 28 shows some
of these system elements: an implantable vertebral plate 100, a
cutting tool guide 200, a confirmation device or depth gauge 300, a
collar 310 for the confirmation device, a cutting tool 400, an
implantable device 500, and an implant locking device 600.
[0096] An implantable vertebral plate 100 is adapted to attach to
the anterior surface of a vertebra. A trajectory control sleeve 200
is adapted to detachably mount the implanted bone plate 100 to
establish the entry point, trajectory, and depth of an access
channel created through the vertebral body. A confirmation device
300 is adapted to temporarily engage the cutter tool guide for the
purposes of confirming placement of the trajectory control sleeve
on the correct vertebra, for visualizing the projected trajectory
of the bone cutting device, and for measuring the actual distance
between the trajectory control sleeve and the anterior bone surface
so as to accurately and predictably penetrate through the vertebra
without impinging on the dura-mater or other neural tissue at the
posterior aspect of the channel. The pin-shaped confirmation device
300 is typically radio-reflective or radiopaque, thus allowing
confirmation of all geometries on a surgical radiograph taken prior
to the excision of any tissue.
[0097] A cutting tool 400 is generally adapted to remove bone
material and create the vertebral access channel; the tool 400 has
the precise cutting geometry necessary to produce the prescribed
access channel geometry within the vertebral bone. The access
channel provides various forms of advantage for aspects of
procedures as described further below.
[0098] A surgical cutting instrument is used to open or partially
remove the posterior longitudinal ligament which can obscure a view
of the pathology of interest, but becomes observable by way of the
access channel. A cutting tool used to remove osteophytes (bone
spurs) at or adjacent to the base of the vertebral body can be
approached by way of the access channel proximal to the neural
elements to be decompressed. An instrument for grasping or moving
herniated disc material or other compressing pathology can be
provided access to the site located at or near the base of the
access channel.
[0099] An implantable bone repair device 500 is adapted repair the
vacant vertebral volume created by the formation of the access
channel.
[0100] An implant locking device 600 is adapted to retain the
implant in the desired position. The locking device is adapted to
positively engage the anterior surface of the repair implant and
engagably lock it in place with respect to the implanted bone plate
device 100. Fasteners such as elements 600 and 900 (seen in later
figures) are applied to retain a bone plate or locking cap (see in
other figures) in a desired position.
[0101] Each of these aforementioned system elements and their role
in surgical procedures on the spine are described in further detail
below.
[0102] FIGS. 1 and 2 show anterior and posterior views,
respectively, of an implantable transcorporeal bone plate device
100 with a first or anterior facing surface 101 and a second or
posterior facing surface 102, the posterior facing surface being
configured to be proximal or in contact with the anterior surface
of a vertebral body after implantation. The device further has one
or more holes 103 that form an aperture between surfaces 101 and
102 to accommodate and secure retention screws there to secure the
device 100 to vertebral bone.
[0103] Embodiments of implantable bone repair described and
depicted herein are may include a multiple number of orifices, as
for example, for inserting attachment elements, or for viewing,
that have various sizes and typically are circular or ovular in
form. These are merely exemplary forms and profiles of openings
which may vary depending on particulars of the application of the
device, such that size and profile may vary, and for example, by
taking the form of any of circular, trapezoidal, multilateral,
asymmetrical, or elongated openings.
[0104] The device also has a passage 104 for receiving and
detachably-engaging a bone cutting guide device such as a drill or
ream. The device 100 further may have one or more engaging features
105 configured to receive and engage a corresponding feature on the
trajectory control sleeve in a manner that prevents relative motion
of the trajectory control sleeve and its accidental disengagement
from the implanted bone plate. The device may have one or more
protrusions 106 on the posterior surface (FIG. 2), the protrusions
being adapted to impinge into or through the cortical bone so as to
increase the stability of the implant on the bone and to allow for
temporary placement of the device prior to insertion of the bone
screws through the opening 103. Protrusions 106 further act to
stabilize the bone implant and to transfer loads around the
vertebral access channel after a surgical procedure is complete,
thereby further reducing the risk of bone fractures or repair
device expulsion.
[0105] FIGS. 3A-3C show a side view and perspective view,
respectively, of an embodiment of a trajectory control sleeve 200
for a bone cutting tool, a rotary cutting tool, for example, such
as a drill, burr, reamer, or trephine. FIG. 3A shows a trajectory
control sleeve in a side view, while FIG. 3C shows the trajectory
control sleeve from a proximally-directed perspective. The
trajectory control sleeve 200 has an internal cylinder 202 there
through to allow passage of a bone-cutting tool, such as a drill or
trephine, and to establish and control the angle a of penetration
of the drill through a vertebral body. As seen in FIG. 3B the angle
a refers to the angular difference from a right angle approach with
respect to the plane formed by an implantable bone plate 100 to
which the trajectory control sleeve is engaged. More specifically,
angle a can represent a compound angle according to a cranio-caudal
axis and a medial lateral axis with respect to a reference plane
tangential (such as would be represented by an implanted bone
plate) to the access channel entry on the anterior surface of
vertebral body. The angle a is prescribed by a physician by making
use of radiographic images of the spine that focus on the target
vertebrae and the underlying pathology that are the subject of
surgical or diagnostic interest. Such procedures are typically
performed prior to surgery, and they may be repeated after the bone
plate is attached to the surgical site. FIG. 3C provides a cross
sectional view of an exemplary control sleeve 200, which shows the
tilt of the annular ring 203 in accordance with angle .alpha., and
the consequent off-center opening at the base of the trajectory
sleeve, which generally aligns with the base of the bone plate when
the two components are engaged.
[0106] In some embodiments of the system and method, a
transcorporal access channel is formed using a trephine type device
such as those provided by Synthes, Inc (West Chester Pa.), which
offers particular advantages. The trephine device produces a
cylindrical channel through the vertebral bone while maintaining
the core to be removed in an intact state. The core can be removed
from the trephine after the tool itself has been removed from the
vertebral body, and the bone tissue can be subsequently re-used as
graft volume after the surgical procedure is completed.
[0107] Trajectory control sleeve 200 has a surface 201 adapted to
be in intimate contact with and be co-planar to an anterior facing
surface 101 of a bone plate implant device 100 (after engaging the
device, as in FIG. 4) so as to assure that the axial distance d is
well established and controlled. The trajectory control sleeve 200
further has an annular abutting surface 203 surrounding the opening
of the internal cylinder 202, the surface being adapted to
positively engage a corresponding feature such as a flange or
collar of the drill so as to prevent its over-penetration into the
vertebral body. This abutment may be internal or external to the
guide device as shown in FIG. 4 and FIG. 3A respectively.
Trajectory control sleeve 200 also has an engaging and interlocking
feature 204 adapted to detachably-engage a corresponding feature
105 (see FIG. 5) on the implantable bone plate 100. The trajectory
control sleeve 200 is further generally adapted to protect
surrounding vascular and soft tissue from accidental injury or
cutting by providing a solid protective sheath around the sharp
edges of the drill while it is operating.
[0108] FIGS. 4 and 5 show a perspective view and side view,
respectively, of trajectory control sleeve 200 and an implantable
bone plate 100 in their mutually interlocked positions. FIG. 4
shows the internal cylinder 202 for providing access, guiding and
controlling the penetration of a drill into vertebral bone. FIG. 4
further shows an alternate embodiment of the device that has an
abutting surface 203, in which the abutting surface is internal to
the trajectory control sleeve. FIG. 5 shows the planar engagement
of the anterior surface of an implanted bone plate 101 with the
corresponding surface 201 of the trajectory control sleeve. This
engagement establishes a reference plane 210 from which angle a and
distance d are controlled and referenced relative to the vertebral
body. FIG. 5 further shows the engagement of the detachable locking
features 205 of the trajectory control sleeve and of the bone plate
105.
[0109] FIGS. 6-8 relate to the placement of a mutually-engaged bone
plate 100 and a trajectory control sleeve 200 to a vertebral body
230, in preparation for creating an access channel through the
vertebral body. FIG. 6 provides a surface perspective view of bone
plate 100 in an implanted position on a vertebral body 230, the
plate secured by a bone screw 900, and further shows trajectory
control sleeve 200 in its engaged position on the bone plate 100.
FIG. 7 shows an anterior view of a bone plate 100 and trajectory
control sleeve 200 mutually engaged and, the engaged assembly in it
installed position on vertebral body 230. A bone screw 900 is
inserted at or near the medial centerline 231 of the vertebral body
230, thus positioning the center point 220 of the trajectory
control sleeve cylinder at a prescribed distance 1 from the
centerline. As seen in FIG. 8, an angle .beta. is the compliment to
angle a shown in FIG. 5. After installation of the bone plate
implant 100 on a vertebral body 230, the reference plane 210 may be
delineated relative to the vertebral body 230 and as a baseline
reference for the angle and depth of drill penetration into the
vertebral body.
[0110] FIGS. 9A and 9B show a pin or plug type confirmation device
300 used for confirming vertebral position prior to excision of
bone or other tissue and a collar 310 into which the confirmation
device is inserted. A standard procedure in spinal surgery is to
insert a radiographically reflective screw or pin into the
vertebral body and to take an x-ray of the cervical spine prior to
beginning any procedure so as to assure that the procedure is being
performed at the correct vertebral level. In the embodiment
described the confirmation device 300 is slidably inserted within
the internal diameter of the control sleeve 200 and progressed
axially therethrough until the proximal end of the device 300 is in
contact with the anterior surface of the vertebral body. A
radiographic image is taken inter-operatively and reviewed prior to
the excision of any vertebral bone tissue. The examination includes
an extrapolation of the trajectory through the vertebral body so as
to confirm that the actual point of exit at the posterior surface
of the vertebra is at the surgically prescribed location. Further,
the axial distance from the both the anterior and/or posterior
surfaces of the vertebra are measured and used as references to
control the depth of bone cutting necessary to produce the access
channel and to prevent over penetration into the dura mater or
neural tissue. In some instances the device 300 may be used during
the bone cutting procedure as a checking device to determine the
actual progression of the channel across the vertebra.
[0111] FIG. 9B shows a trajectory confirmation pin 300 and a collar
310 that slidably-engages the external diameter of the pin by way
of features 320 that engage complementary features 321 on the
internal diameter of the collar. In this exemplary embodiment, the
trajectory pin features 320 are convexities that are complementary
to concave collar feature 321. Collar 310 can slide axially along
the length of the pin diameter 320 and frictionally-engage the pin
diameter in a manner that requires an axial force to be applied to
the collar to induce axial movement. Collar 310 has a surface of
engagement feature 330 that is adapted to make intimate contact
with the annular surface 203 of the trajectory control sleeve when
the pin is inserted into the trajectory control sleeve. Once
surfaces 203 and 330 are engaged, insertion force F (FIG. 9A)
applied by a surgeon causes pin 300 to travel axially through the
internal diameter of collar 340, increasing the distance L2 between
point 350 on the tip of the pin and the control surface 330 of the
collar 310.
[0112] FIGS. 10-12 relate to the use of a trajectory confirmation
pin 300, a collar 310, and trajectory control sleeve 200 in the
context of a bone plate 100 in place, as implanted in a vertebral
body 230. An embodiment of a pin device 300 is temporarily inserted
into the internal cylinder of the trajectory control sleeve 200 and
an x-ray is taken. The x-ray confirms the location of the vertebral
body 230 and an anterior-to-posterior extrapolation along the
centerline of the device through the image of vertebral body
indicates the trajectory of the drill or cutting tool and the
projected point of exit at or near the posterior longitudinal
ligament. Angular and distance measurements may be made using the
radiograph, and if adjustments are required, the surgeon disengages
the trajectory control sleeve and installs another device with the
desired geometry.
[0113] FIG. 11 shows the confirmation pin 300 at its maximum depth
of penetration through the transparently rendered trajectory
control sleeve 200 and bone plate implant 100. In this position,
tip 350 of the pin device is in intimate contact with the surface
of the vertebral bone 230. Because of the mechanical engagement of
the collar 310 on the external surface, the collar remains in
position relative the bone-contacting tip of the pin 350. Upon
removal of the pin, distance L2 (see FIG. 9A), as measured between
the collar surface 330 and the pin contact tip 350, provides a
reference dimension with which the penetrating depth of the bone
drill can be controlled by setting a mechanical stop that engages
the annular surface 203 of the trajectory control sleeve. For ease
of use, the surface of the confirmation pin 300 may have linear
graduations.
[0114] FIG. 13 shows a bone cutting tool 400, such as a drill,
burr, or reamer, inserted through the trajectory control sleeve 200
and the bone plate implant 100 with the tip of the cutting tool 420
at the initial point of contact on the vertebral body. Cutting tool
400 has a mechanical stop 450. The distance D4 from the drill tip
420 to the lower surface 430 of the drill stop 450, is a prescribed
dimension equivalent to the measured distance L2 (see FIG. 9A) plus
the desired depth of penetration into the vertebral body, such
depth being established by the surgeon through radiographic
analysis.
[0115] FIG. 14 shows a surgical access channel 470 in a vertebral
body 230, as viewed through the bone plate implant 100 after
drilling has been completed and the trajectory control sleeve has
been removed from the plate. After removal of the trajectory
control sleeve, a neural decompression or other surgical procedure
is performed through the access channel. On completion of the
procedure, an intra-vertebral bone implant 500 is inserted (FIGS.
15 and 16) into access channel 470 to fill an close it, restore
mechanical strength and stability to the host vertebral body 230,
and to provide a medium within the vertebral body suitable for
osteogenesis.
[0116] In some embodiments of the invention, the intra-vertebral
access channel 470 (FIG. 14) of an implantable bone plate has a
diameter of about 5 mm to about 8 mm. This size creates a surgical
field that is sufficiently open enough for typical procedures, and
is sufficiently large enough to minimize the possibility that the
access channel will not intersect the area of neural compression.
In some embodiments, the angle of entry a provided by the access
channel is about 10-30 degrees, with the center of the point of
entry being generally at mid-point on the cranio-caudal length of
the vertebra. While these dimensions are typical, alternative
embodiments of bone plate implants may have varying widths and
geometries so as to accommodate wide anatomical variations. In
various alternative embodiments, trajectory control sleeve devices
also may include a wide range of angles and depths for the same
reason.
[0117] With a combination of the angle of entry, the point of entry
into the vertebral body, and the size of drill used to create the
access channel 470, some embodiments may result in a penetration of
the posterior disc space in the posterior 20%-30% of the disc
volume 480, leaving the vertebral end plate 490 and the native disc
tissue 495 substantially intact. FIG. 29 illustrates a typical
access channel 470 that may be formed using a 6 mm drill diameter,
about a 10 degree angle of entry, with an entry point on the
cranio-caudal centerline of the vertebral body.
[0118] FIG. 15 shows an intra-vertebral implantable bone repair
device 500 positioned for implantation within the vertebra 230
through the bone plate implant 100. Various embodiments and
features of a bone repair device are described in U.S. Provisional
Patent Application No. 60/990,587 of Lowry et al. (filed on Nov.
27, 2007, entitled "Methods and systems for repairing an
intervertebral disk using a transcorporal approach"), which is
incorporated herein in its entirety by this reference. In the
embodiment shown, implant 500 has an abutting surface 520 adapted
to engage with a corresponding surface of the bone plate implant.
This arrangement prevents excess penetration of the implant through
the access channel and prevents the implant from compressively
engaging neural elements. FIG. 16 shows the implantable device 500
in the final installed position relative to the bone plate 100. The
device 500 has a locking mechanism 510, such as a conventional
bayonet mount, for engaging the bone plate in order to prevent
migration of the implant within or out of the access channel.
[0119] FIG. 17 shows an alternative embodiment 620 of an
implantable bone plate as previously described and shown in FIGS. 1
and 2. In this present embodiment, bone plate 620 has a larger
lateral dimension to accommodate particular anatomies that may be
encountered, including those of patients, for example, with small
stature, degenerative bone conditions, or osteophytes or other
abnormalities that may require alternate fixations. To assure
accurate location of the device relative to the medial centerline
of the vertebra, implant device 620 may include a viewing port 650
or some other positioning indicator. FIGS. 18A and 18B show
anterior perspective and side views, respectively, of the
engagement of a trajectory control sleeve 200, as previously
described, with the alternative bone implant device embodiment
620.
[0120] In another alternate embodiment, an implantable bone plate
and bone cutting device may be formed as a unitary device and
temporarily fixed to the vertebral body. In this embodiment an
intra-vertebral access channel is created using the temporarily
implanted device; subsequently, the device is removed, the surgical
procedure performed, and the access channel repaired using the
intra-vertebral implant as previously described. In this
embodiment, a bone cutting device may have a least two cutting
diameters or widths, the first being that necessary to produce the
access channel, the second being a larger diameter configured to
remove an annulus of bone on the anterior vertebral surface so as
to provide an abutting surface against which the implant would rest
in order to prevent over-penetration of the intra-vertebral repair
implant within the vertebra.
[0121] FIGS. 19-24 show exemplary devices being put to exemplary
use to evaluate the practical viability, fit, and the functionality
of methods for their use. FIG. 19 shows an implantable bone plate
100 in situ on a vertebral surface 230. FIG. 20 shows a perspective
view of the implantable bone plate and trajectory control sleeve
200 in situ on the vertebral surface. FIGS. 21-24 include a view of
surgeon's finger to show scale and feasibility of manual
manipulation of elements of the inventive system. FIG. 21 shows a
bone cutting tool 400 engaging vertebral bone tissue through the
trajectory control sleeve 200. FIG. 22 shows an access channel 470
through the implanted bone plate and into vertebral bone tissue.
FIG. 23 shows an intra-vertebral repair device 500 being readied
for engaging vertebral bone through the bone plate 100.
[0122] FIGS. 25A-27B show embodiments of alternative external
geometries of the intra-vertebral implantable devices 500 as may
appropriate for particular patients or procedures. FIGS. 25A and
25B show views of what may be considered a default embodiment of an
intravertebral repair device with a proximal abutting surface
orthogonal to the body of the device. FIG. 25A shows the device
from a proximally-directed perspective, while FIG. 25B shows it
from a distally-directed perspective. FIGS. 26A and 26B show and
embodiment wherein abutting surface 520 is canted at an angle not
orthogonal to the central axis of the device 500. FIGS. 27a and 27b
show an intra-vertebral implant device 500 with a convex external
profile where dimension D4 is nominally larger than the internal
diameter of the access channel so as to compressively engage the
cancellous bone tissue. Such a compressive engagement can improve
the interference fit of the device therein and to inter-diffuse
cancellous bone tissue within the implant volume to improve
osteogenesis.
[0123] FIG. 28 shows an assemblage of some of these system
elements, and was described at the outset of the detailed
description; shown is an implantable vertebral plate 100, a cutting
tool guide 200, a confirmation device or depth gauge 300, a collar
310 for the confirmation device, a cutting tool 400, an implantable
device 500, and an implant locking device 600. FIG. 29 provides an
exemplary embodiment of the invention that was discussed earlier in
the context of the formation of an access channel, in conjunction
with associated description of FIGS. 14-16.
[0124] Implantation of the patient's own bone tissue (an autologous
graft) is a generally advantageous approach to repairing bone, as
autologous grafting typically yields high success rates and a low
rate of surgical complications. Accordingly, some embodiments of
the invention include using core bone tissue harvested from the
forming of the access channel, and implanting the plug, intact, in
the form of bone repair graft. An advantage to recovering and
making use of bone derived from the channel includes the absence of
a need to harvest bone from a second site. Embodiments of the
invention, however, do include harvesting bone from secondary sites
on the patient, such as the iliac crest, as may be appropriate in
the practice of the invention under some circumstances. In some
embodiments, for example, it may be advantageous to supplement bone
derived from the access channel with bone from other sites. In
still other embodiments, under various clinical circumstances, it
may be appropriate to make use of bone from donor individuals. Bone
from other autologous sites or other donor individuals may be used
as a repair device in the form of an appropriately formed plug, or
bone may be fragmented or morselized, and packaged as a solid plug,
or bone may be included as a preparation provided in a porous cage,
as described further below.
[0125] Some embodiments of methods provided make use of a trephine
type bone cutting system, as noted above. With a trephine bone
cutting system, the external diameter of the bone tissue core is
about equal to the internal diameter of the trephine device, while
the internal diameter of the access channel is about equal to the
external diameter of the device. Thus, a trephine-derived bone plug
from forming the access channel provides an appropriately-sized
piece to be inserted into the channel for repair and healing, but
does not necessarily make intimate contact with the inside surface
of the channel due to the width of the kerf created by the
trephine.
[0126] Optimal healing and recovery from implantation of bone
material into an access channel occurs when there is an intimate or
compressive engagement of the graft material with the vertebral
bone tissue (substantially cancellous bone), as this intimate
association provides for rapid blood profusion and bone healing
while providing mechanical support during healing. Accordingly, an
embodiment of the bone repair device provided herein includes a
device with bone tissue inside a porous cage, as described in
detail below.
[0127] The porosity of the cage is a particularly advantageous
feature for allowing cell to cell contact through the boundary of
the device. To some degree, it may also allow cell migration,
however the most advantageous factor in promoting rapid healing is
cell to cell contact that initiates sites of tissue unification,
which can then spread, stabilize a healing zone around the graft or
bone repair device, and ultimately lead to effective fusion and
integration of the graft within the host vertebral body.
[0128] A porous cage, as provided by this invention, also has a
compressibility, such that when the contents of the cage are
subject to a compressive force, however transient and minimal,
blood or plasma and bone cells that are present in the harvested
cancellous bone are forced outward into the environment within and
around the access channel site. Extrusion of biological fluid in
this manner, advantageously packs bone tissue closer together
within the cage, and bathes the periphery of the graft and the
host-graft intersectional zone with a medium that is optimal for
exchange of dissolved gas and nutrients that are critical in the
initial stages of healing. Some embodiments of the invention
include bathing the bone tissue preparation in a supportive liquid
medium before implantation. Such bathing may occur prior to placing
the bone tissue preparation in the porous cage and/or after placing
the preparation in the cage. The liquid medium may be any
appropriate cell culture medium, and may be further supplemented
with biological agents, such as osteogenic agents or other growth
factors.
[0129] Embodiments of the implantable porous cage bone repair
device, as provided herein, encapsulate the bone tissue contained
therein, and provide mechanical stability to the access channel
during healing. These embodiments compensate for the volumetric
loss associated with the bone cutting process of the trephine and
promote contact between the bone volume within the device and the
surrounding vertebral bone tissue. The device, as a whole, and like
other bone repair embodiments provided, cooperates with the
implanted bone plate so that the orientation and penetration depth
of the implant device within the access channel may be controlled.
These forms of control assure that the device does not
over-penetrate through the channel, thereby compressing the dura
mater or neural elements within the vertebra, and assuring that the
implanted device cannot migrate in an anterior direction out of the
access channel.
[0130] Exemplary embodiments of the porous cage device and
associated method of use will now be described in further detail,
and in the context of FIGS. 30-37.
[0131] FIG. 30 provides a cross-sectional view of a vertebral body
809 with a bone plate 801 attached to the anterior bone surface
810. Mounted on the bone plate is a trajectory control sleeve 802
cooperating with the bone plate 801 to establish and control the
trajectory of a bone cutting tool 804 with a cutting surface 808
through the vertebral body to direct the trajectory of the formed
access channel to a prescribed point of exit at the posterior
surface of the vertebra 820, in the locale of a site of medical
interest.
[0132] The depicted exemplary bone cutting tool 804 is a hollow
bone cutting tool, a trephine, with an external diameter 805
selected to be complementary to the internal diameter of the
trajectory control sleeve 802, and to cooperate therewith so as to
assure that the centerlines of the bone cutting tool and the
trajectory control sleeve are substantially co-incident during the
bone cutting process. The trephine 804 progresses through the
vertebral body 820 from an anterior to posterior direction until
the cutting surface 808 penetrates the cortical bone at the
posterior surface of the vertebra proximal to the spinal cord 850.
Upon removal of the trephine from within the vertebral body, a core
of bone tissue within the interior of the trephine is extracted
from the wound opening, thus creating or exposing an open access
channel from the anterior surface of the vertebral body to the
neural elements and the prescribed site of medical interest
immediately behind the posterior wall of the same vertebral
body.
[0133] FIG. 31 shows components of an exemplary bone repair device
in a linearly exploded view from an external perspective. At the
top, a cap 950 is above a vertebral bone core 860; the bone core is
positioned for placement in a porous cage 900. FIG. 32 is a
cross-sectional view of the fully assembled device 905. According
to the inventive method, the vertebral bone core 860 is placed
within an implantable intravertebral bone repair device 900 with a
porous wall, and encapsulated by a cap or closing element 950. In
this exemplary embodiment the cap has a screw thread 951 disposed
to engage a mating thread 901 on the body 900 of the implantable
device; the cap further has a compression element 952 disposed to
exert a compressive force F on the bone graft core 860 when the cap
is being closed on the body 900 of the repair device, and
consequently inducing extrusion of native tissue within the device,
through open pores 902 contained within the perimeter wall of the
implant device. As described above, the bone tissue placed within
the body of the repair device is not necessarily an integral bone
plug intact from the trephine used to form the channel; the bone
tissue may be a fragmented or morselized preparation, it may
include bone from another site on the patient, and it may include
bone from another donor.
[0134] FIG. 33 provides an external perspective view of an
assembled bone repair device 905. This view captures a moment
shortly after the cap 950 has been closed, and by such closing has
increased the pressure on the bone tissue contained within the
device. By virtue of this elevated pressure within the porous
walled body 900, bone core graft tissue and associated biological
fluid are extruding through the porous perimeter wall. In some
embodiments of the method, the cap 950 is closed on the porous body
900 of the repair device immediately prior to insertion of the
assembled device 905 into the access channel within the host
vertebral body, and in some embodiments of the method, the cap is
closed after insertion of the porous body 900, thereby forming the
complete assembly 905 in situ.
[0135] FIG. 34 shows a cross sectional view of an alternate
embodiment of the porous body portion 900' of an assembled repair
device 905' that includes an internal tissue expander feature 920
disposed to induce radial extrusion of the bone core tissue through
the orifices.
[0136] FIGS. 35 and 36 show similar views of the porous cage device
embodiment 905 as were provided earlier by FIGS. 15 and 16 for
solid bone repair device 500 embodiments. FIG. 37 shows a cross
sectional view of the implanted device 905 within an intravertebral
access channel 470. Upon completion of the surgical procedure
through the access channel, the bone repair implant assembly 905
(containing the harvested bone graft core 860) is introduced into
the transcorporal access channel through the aperture 830 in the
implanted bone plate device 100. In one exemplary embodiment, the
bone repair assembly 905 has an abutting surface disposed to
cooperate with a mating surface of engagement 871 on the bone plate
implant. The completed mating of the bone repair assembly 905 with
the bone plate 100 prevents the distal tip 890 of the implant
assembly from penetrating into the spinal cord volume posterior to
the vertebral body.
[0137] The implantable repair device assembly 905 further has an
orientation and locking feature 951 disposed to engage a mating
feature 950 on the implantable bone plate 100 so as to control the
radial orientation of the implant with respect to the bone plate
and to lockably engage the bone repair implant device with the bone
plate implant so as to prevent migration or expulsion of the bone
repair implant assembly 905 out of the access channel. Such radial
orientation of the implant relative to the access channel may be
particularly advantageous when the bottom or distal end of the
repair device body 900 is formed at an angle (not shown) to
completely fill the access channel.
[0138] As a consequence of the implantation of the bone repair
assembly 905 within the access channel, the general mechanical
integrity of the vertebral body has been restored, the internal
void of the access channel has been filled in a manner such that
native disc material 980 cannot migrate into the channel, bone
tissue (typically autologous) has been re-implanted in a manner
that establishes intimate contact between the bone graft and the
cancellous bone of the vertebra thereby promoting blood profusion
and rapid bone healing.
* * * * *