Prostheses, Systems and Methods for Replacement of Natural Facet Joints With Artificial Facet Joint Surfaces
Cephalad and caudal vertebral facet joint prostheses and methods of use are provided. The prostheses provide an artificial facet joint structure including an artificial articular configuration unlike the preexisting articular configuration. The radii and material stress values of the prostheses are configured to sustain contact stress. The cephalad prosthesis provides for posterior-anterior adjustment. Both prostheses permit lateral adjustment and adjustment to accommodate interpedicle distance. Further, the prostheses may be customized to provide a pre-defined lordotic angle and a pre-defined pedicle entry angle.
This application is a continuation of Ser. No. 11/197,679, filed Aug. 3, 2005 entitled “Implantable device for facet joint replacement”, which is a continuation of U.S. Non-Provisional application Ser. No. 10/158,563, filed May 30, 2002, entitled “Prostheses Systems and Methods for Replacement of Natural Facet Joints With Artificial Facet Joint Surfaces” (now U.S. Pat. No. 6,974,478), which is a Continuation-in-Part of application Ser. No. 10/067,137, filed Feb. 4, 2002, entitled “Facet Arthroplasty Devices and Methods”, (now U.S. Pat. No. 6,811,567) which is a Continuation-in-part of application Ser. No. 09/963,272, filed on Oct. 20, 2000, entitled, “Facet Arthroplasty Devices and Methods”, (now U.S. Pat. No. 6,610,091) which claims priority to U.S. Provisional Patent Application Ser. No. 60/160,891, filed Oct. 22, 1999, entitled “Facet Arthroplasty Devices and Methods,” which is incorporated herein by reference.
FIELD OF THE INVENTIONThis invention relates to prostheses for treating various types of spinal pathologies, as well as to methods of treating spinal pathologies.
BACKGROUND OF THE INVENTIONI. Vertebral Anatomy
As
At the posterior end of each pedicle 16 the vertebral arch 18 flares out into broad plates of bone known as the laminae 20. The laminae 20 fuse with each other to form a spinous process 22. The spinuous process 22 serves for muscle and ligamentous attachment. A smooth transition from the pedicles 16 into the laminae 20 is interrupted by the formation of a series of processes.
Two transverse processes 24 thrust out laterally on each side from the junction of the pedicle 16 with the lamina 20. The transverse processes 24 serve as levers for the attachment of muscles to the vertebrae 12. Four articular processes, two superior 26 and two inferior 28, also rise from the junctions of the pedicles 16 and the laminae 20. The superior articular processes 26 are sharp oval plates of bone rising upward on each side from the union of the pedicle 16 with the lamina 20. The inferior processes 28 are oval plates of bone that jut downward on each side.
The superior and inferior articular processes 26 and 28 each have a natural bony structure known as a facet. The superior articular facet 30 faces 30, while the inferior articular facet 31 faces downward. As
The facet joint 32 is composed of a superior half and an inferior half. The superior half is formed by the vertebral level below the joint 32, and the inferior half is formed by the vertebral level above the joint 32. For example, in the L4-L5 facet joint, the superior portion of the joint is formed by bony structure on the L-5 vertebra (e.g., a superior articular surface and supporting bone on the L-5 vertebra), and the inferior portion of the joint is formed by bony structure on the L-4 vertebra (e.g., an inferior articular surface and supporting bone on the L-4 vertebra).
As also shown in
II. Facet Joint Dysfunction
Back pain, particularly in the “small of the back”, or lumbosacral (L4-S1) region, is a common ailment. In many cases, the pain severely limits a person's functional ability and quality of life. Such pain can result from a variety of spinal pathologies.
Through disease or injury, the laminae, spinous process, articular processes, or facets of one or more vertebral bodies can become damaged, such that the vertebrae no longer articulate or properly align with each other. This can result in an undesired anatomy, loss of mobility, and pain or discomfort.
For example, the vertebral facet joints can be damaged by either traumatic injury or by various disease processes. These disease processes include osteoarthritis, ankylosing spondylolysis, and degenerative spondylolisthesis. The damage to the facet joints often results in pressure on nerves, also called a “pinched” nerve, or nerve compression or impingement. The result is pain, misaligned anatomy, and a corresponding loss of mobility. Pressure on nerves can also occur without facet joint pathology, e.g., a herniated disc.
One type of conventional treatment of facet joint pathology is spinal stabilization, also known as intervertebral stabilization. Intervertebral stabilization prevents relative motion between the vertebrae. By preventing movement, pain can be reduced. Stabilization can be accomplished by various methods.
One method of stabilization is spinal fusion. Another method of stabilization is fixation of any number of vertebrae to stabilize and prevent movement of the vertebrae.
Another type of conventional treatment is decompressive laminectomy. This procedure involves excision of the laminae to relieve compression of nerves.
These traditional treatments are subject to a variety of limitations and varying success rates. Furthermore, none of the described treatments puts the spine in proper alignment or return the spine to a desired anatomy. In addition, stabilization techniques, by holding the vertebrae in a fixed position, permanently limit a person's mobility.
SUMMARY OF THE INVENTIONThere is a need for prostheses, systems, and methods that overcome the problems and disadvantages associated with current strategies and designs in various treatments for spine pathologies.
The invention provides prostheses, systems, and methods designed to replace natural facet joints and/or part of the lamina at virtually all spinal levels including L1-L2, L2-L3, L3-L4, L4-L5, L5-S1, T-11-T12, and T12-L1. The prostheses, systems, and methods can restore a desired anatomy to a spine and give back to an individual a desired range of mobility. The prostheses, systems, and methods also can lessen or alleviate spinal pain by relieving the source nerve compression or impingement.
For the sake of description, the prostheses that embody features of the invention will be called either “cephalad” or “caudal” with relation to the portion of a given natural facet joint they replace. As previously described, a given natural facet joint has a superior half and an inferior half. In anatomical terms, the superior half of the joint is formed by the vertebral level below the joint (which can thus be called the caudal portion of the facet joint, i.e., because it is near the feet). The inferior half of the joint is formed by the vertebral level above the joint (which can thus be called the cephalad portion of the facet joint, i.e., because it is near the head). Thus, a prosthesis that, in use, replaces the caudal portion of a facet joint (i.e., the superior half) will be called a “caudal” prosthesis. Likewise, a prosthesis that, in use, replaces the cephalad portion of a facet joint (i.e., the inferior half) will be called a “cephalad” prosthesis.
One aspect of the invention provides a facet joint prosthesis to replace, on a vertebral body, a caudal portion of a natural facet joint (e.g., a superior articular surface and supporting bone structure on the vertebral body). The caudal prosthesis comprises a component sized to be fixed to the vertebral body, e.g., on or near a pedicle. The caudal prosthesis includes an artificial facet joint structure adapted to replace a caudal portion of the natural facet joint after its removal from the vertebral body. The removal of a caudal portion of the natural facet joint and its total replacement by the artificial facet joint structure of the caudal prosthesis frees the orientation of the prosthesis from anatomic constraints imposed by a preexisting articular configuration of the caudal portion of the natural facet joint. Furthermore, the artificial facet joint structure of the caudal prosthesis can comprise an artificial articular configuration that is unlike the preexisting articular configuration, so that a desired articulation or bony anatomy can be restored.
This aspect of the invention also provides a method of replacing, on a vertebral body, a caudal portion of a natural facet joint. The method removes a caudal portion of the natural facet joint from the vertebral body, and, in its place, fixes a component to the vertebral body that includes an artificial facet joint structure adapted to replace the removed caudal portion of the natural facet joint. The artificial facet joint structure can include an artificial articular configuration unlike the preexisting articular configuration of the removed caudal portion of the natural facet joint.
Another aspect of the invention provides a facet joint prosthesis to replace, on a vertebral body, a cephalad portion of a natural facet joint (e.g., an inferior articular surface and supporting bone structure on the vertebral body). The cephalad prosthesis comprises a component sized to be fixed to the vertebral body, e.g., on or near a pedicle, or on or near a lamina, or on or near a spinous process, or combinations thereof. The cephalad prosthesis includes an artificial facet joint structure adapted to replace a cephalad portion of the natural facet joint after its removal from the vertebral body. As with the removal and total replacement of a caudal portion of the natural facet joint, the removal of a cephalad portion of the natural facet joint and its total replacement by the artificial facet joint structure of the cephalad prosthesis makes possible the orientation of the prosthesis free from anatomic constraints imposed by a preexisting articular configuration of the cephalad portion of the natural facet joint. Furthermore, like the caudal prosthesis, the artificial facet joint structure of the cephalad prosthesis can comprises an artificial articular configuration that is unlike the preexisting articular configuration of the natural facet surface (which is removed), so that a desired articulation or bony anatomy can be totally restored.
This aspect of the invention also provides a method of replacing, on a vertebral body, a cephalad portion of a natural facet joint. The method removes a cephalad portion of the natural facet joint from the vertebral body, and, in its place, fixes a component to the vertebral body that includes an artificial facet joint structure adapted to replace the removed cephalad portion of the natural facet joint. The artificial facet joint structure can include an artificial articular configuration unlike the preexisting articular configuration of the removed cephalad portion of the natural facet joint.
Another aspect of the invention provides a prosthesis assembly and related method for replacing a natural facet joint between adjoining first and second vertebral bodies. The assembly and method utilize a first component sized to be fixed to the first vertebral body, which is superior to the second vertebral body. The first component includes a first artificial facet joint structure adapted to replace a cephalad portion of the natural facet joint on the first vertebral body after removal of the cephalad portion of the natural facet joint from the first vertebral body. The assembly and method also comprise a second component sized to be fixed to the second vertebral body. The second component includes a second artificial facet joint structure adapted to replace the caudad portion of the natural facet joint of the second vertebral body after removal of the caudad portion of the natural facet joint from the second vertebral body. Together, the first and second artificial facet joint structures comprise an artificial facet joint. The removal of both cephalad and caudal portions of a natural facet joint and their total replacement by the artificial facet joint structures of the first and second components allows the artificial facet joint to be installed without anatomic constraints imposed by a preexisting articular configuration of the natural facet joint. Furthermore, the artificial facet joint structures of either the first or second components, or both, can comprise create an artificial articular configuration for the artificial facet joint that is unlike the preexisting articular configuration of the removed natural facet joint, so that a desired articulation or bony anatomy can be completely restored.
Various other aspects of the invention provide caphalad and/or caudal prostheses that readily adapt to or physically change the specific anatomy of an individual. For example, a cephalad prosthesis can be capable of being adjusted in either an anterior or posterior direction relative to a vertebra. As another example, a cephalad prosthesis and/or a caudal prosthesis can provide for lateral (left and right) adjustment, to accommodate or create variances in the distance between the right and left pedicles of a single vertebra. Furthermore, a cephalad prosthesis and/or a caudal prosthesis can provide vertical (up and down) adjustment, to accommodate or create variations in interpedicle distance between adjacent vertebra. Or, as another example, a cephalad prosthesis and a caudal prosthesis can together create a desired lordotic angle between adjacent vertebral bodies, or create a pre-defined pedicle entry angle for mounting each prosthesis on a given vertebral body. And, as yet another example, the configuration of articulating artificial facet joint structures on cooperating caphalad and caudal prostheses can be matched, taking into account the material(s) from which they are made, to minimize contact stress.
Another aspect of the invention provides an intermediate prosthesis that, together with the cephalad and caudal prostheses, makes possible multiple-level facet joint replacement.
Other features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended Claims.
DESCRIPTION OF THE DRAWINGS
The invention may be embodied in several forms without departing from its spirit or essential characteristics. The scope of the invention is defined in the appended claims, rather than in the specific description preceding them. All embodiments that fall within the meaning and range of equivalency of the claims are therefore intended to be embraced by the claims.
DETAILED DESCRIPTIONAlthough the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention that may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
I. VERTEBRAL PROSTHESESFIGS. 4 to 6 illustrate various prostheses for replacing inferior and/or superior portions of natural facet joints. The prostheses are desirably fixed to vertebral bodies following the surgical removal of the respective natural facet joint portions from the vertebral bodies.
Either prosthesis 36 or 38 can be used by itself. The prostheses 36 and 38 each enables bilateral facet joint replacement (both left and right sides of a given vertebral body), or unilateral facet joint replacement (one side of a given vertebral body).
As shown in
As shown in
A. The Cephalad Prosthesis
The prosthesis 36 shown in
The artificial facet joint structures 40 articulate with the superior half of the facet joint 32. The superior half can comprise the natural superior portions of the facet joint 32 (i.e., the natural superior articular surfaces 26 and supporting bony structure on the vertebral body below the facet joint 32). Desirably, however, the superior half comprises an artificial facet joint structure 54 formed by a caudal joint replacement prosthesis 38, shown, e.g., in
The cephalad prosthesis 36 is sized to extend across the laminae 20 of a vertebral body. In the illustrated embodiment, the caphalad prosthesis comprises a chimney 42 and left and right arm components 44.
The chimney 42 is configured to receive the spinous process 22 of the vertebral body. In this manner, the chimney 42 serves to support and stabilize the prosthesis 36. The chimney 42 desirably includes a lamina hook 46 (best shown in
The chimney 42 carries right and left arms 44 in association with the chimney 42. Each arm 44 carries an artificial facet joint structure 40.
As seen in
Each arm 44 additionally carries at least one opening 50 configured to receive a fixation element 52 for fixing the prosthesis 36 to the vertebral body. It should be understood that the number and location of openings 50 and fixation elements 52 could vary.
In
As shown in
The cephalad prosthesis 36 may be formed of a material commonly used in the prosthetic arts including, but not limited to, polyethylene, rubber, titanium, chrome cobalt, surgical steel, bony in-growth sintering, sintered glass, artificial bone, ceramics, or a combination thereof.
B. The Caudal Prosthesis
The prosthesis 36 shown in
In use, the artificial facet joint structure 54 articulates with the inferior half of the facet joint 32. The inferior half can comprise the natural inferior portions of the facet joint 32 (i.e., the natural inferior articular surfaces and supporting bony structure on the vertebral body above the facet joint 32). Desirably, however, the inferior half comprises an artificial facet joint structure 40 formed by a cephalad joint replacement prosthesis 36, as
In the illustrated embodiment, the caudal prosthesis 38 is a bar-like member sized to extend across the laminae 20 of the vertebral body. While
Like the cephalad prosthesis 36, the caudal prosthesis 38 carries at least one opening 56 configured to receive a fixation element 58 for fixing the prosthesis 38 to the vertebral body and at least one artificial facet joint structure element 54. It is to be understood that the number and location of openings and fixation elements can vary.
In
The caudal prosthesis 38 may be formed of a material commonly used in the prosthetic arts including, but not limited to, polyethylene, rubber, titanium, chrome cobalt, surgical steel, bony in-growth sintering, sintered glass, artificial bone, ceramics, or a combination thereof.
II. ADDITIONAL FEATURES OF THE PROSTHESESEither or both of the cephalad and caudal prostheses 36 and 38 can incorporate a variety of additional features, which adapt the prosthesis 36 or 38 to the specific anatomy encountered or desired. These adaptive features further enhance the restoration of a desired anatomy and/or the alleviated of pain, as will be described in greater detail later. As will become apparent to one skilled in the art, any of the following features can be used alone or in combination with any other feature or features, to “customize” a prosthesis 36 or 38 to a given vertebral location and a specific individual.
A. Posterior-Anterior Adjustment
As shown in FIGS. 7 to 11, the cephalad prosthesis 36 can comprise a multiple-piece construction. The multiple-piece construction permits posterior and anterior (i.e., “front and back”) adjustment of the prosthesis 36 relative to the vertebral body. Either symmetric or asymmetric posterior-anterior mounting arrangements are thereby enabled.
In the embodiment shown in FIGS. 7 to 11, the prosthesis 36 is a three-piece assembly comprising a center member 42 (which can comprise the chimney already discussed) and right and left arm components 44. Each arm 44 is a separate piece that is selectively detachable from the center member 42. The arms 44 can be coupled to the center member 42 by a variety of means, including, but not limited to, a slotted joint between the chimney 42 and the respective arm 44, a screw attachment, a hook attachment, or a snap-fit engagement.
A slotted joint or the like allows for relative sliding movement between the respective arm and center member. As best seen in
In an alternative construction (not shown), the center member 42 can comprise one piece and the arms 44 are integrally attached to form a second, discrete piece that is selectively attachable and detachable from the member 42. This arrangement would similarly permit posterior and anterior adjustment of the arms 44, but would not permit independent adjustment of the right and left arms 44.
The orientation of the prosthesis 36 is thus not dictated by the natural posterior-anterior anatomy encountered. Instead, the prostheses 36 can be fixed in position between two vertebral bodies in an orientation that corresponds to existing natural anatomy or that establishes a desired posterior-anterior anatomy unlike the natural anatomy.
B. Lateral Adjustment
As seen in
The horizontal configuration allows the fixation elements 52 and 58 on opposite lateral sides of the prostheses 36 and 38 to be placed anywhere between an “A” position (illustrated by solid lines in
The lateral orientation of the artificial facet joint structures of the prostheses 36 or 38 is thus not dictated by the natural lateral anatomy (i.e., intrapedicular distance) encountered. Instead, the position of the artificial facet joint structures of the prostheses 36 and 38 can be changed relative to the position of the pedicles, either medial to or lateral to the pedicles (establishing a desired lateral anatomy unlike the natural anatomy), or in an orientation that corresponds to an existing natural anatomy.
C. Adjustment of Interpedicle Distance
Referring now to
The vertical configuration allows the fixation elements 52 and 58 to be placed anywhere from an “A” position (illustrated by solid lines in
The orientation of the prostheses 36 and 38 is not dictated by the natural interpedicular distances encountered. Instead, the prostheses 36 and 38 can be fixed in position between two vertebral bodies in an orientation that corresponds with the existing natural anatomy or that establishes a desired interpedicular distance unlike the natural preexisting interpedicle distance. The prostheses 36 and 38 thereby serve to create a desired interpedicular distance for the vertebral bodies consistent with a desired anatomy.
D. Lordotic Angle Adjustment
As shown in
In the illustrated embodiment (see
The defined angle is designated angle “L” in
The orientation of the prostheses 36 and 38 is not dictated by preexisting natural lordotic angle between two vertebral bodies. Instead, the prostheses 36 and 38 can be fixed in position between two vertebral bodies in an orientation that establishes a desired lordotic angle unlike the natural preexisting angle. The prostheses 36 and 38 thereby serve to create a desired lordotic angle for the vertebral bodies consistent with a desired anatomy.
Changes in the thickness of and/or orientation of the artificial facet joint structures on either or both prostheses 36 and/or 38 can also affect a desired lardotic angle between adjacent vertebral bodies.
E. Adjustment of Pedicle Entry Angle
As shown in
To achieve the desired angle, the openings 50 and 56 of adjacent cephalad and caudal prostheses 36 and 38 are mutually tilted inwardly to define between a lateral axis and the fixation elements 52 and 58, when supported by the openings 50 and 56, an angle that approximates a desired pedicle entry angle P1/P2. In the illustrated embodiment (
While the illustrated embodiment shows cephalad and caudal prostheses 36 and 38 having the same pedicle entry angles (i.e., P1 and P2 are the same for the cephalad and caudal prostheses 36 and 38), it is to be understood that the cephalad and caudal prostheses 36 and 38 can be formed to have different pedicle entry angles.
F. Multiple-Level Replacement
As shown in
The intermediate prosthesis 60 is similar to the cephalad prosthesis 36 previously described, having a chimney 42 and two openings (right and left) 50 that receive fixation elements 52. Right and left arms 44 provide a first and second pairs of artificial facet joint structures 64 and 66. The first pair 64 is configured to replace the superior processes 26 and related bony structure of the middle vertebral body, and to articulate with the artificial facet joint surfaces 40 of the cephalad prosthesis 36. The second pair 66 is configured to replace the inferior processes 28 and related bony structure of the middle vertebral body, and to articulate with the artificial facet joint surfaces 54 of the caudal prosthesis 38.
G. Ability to Sustain Contact Stress
In the prostheses 36 and 38, each artificial facet joint structure 40/54 creates a bearing surface having a configuration that facilitates articulation with the bearing surface of another artificial facet joint structure. The particular geometry for the bearing surface configuration for a given artificial facet joint structure 40/54 can vary. It can, for example, be concave, convex, or flat. It may also include a hybrid of curved and flat bearing surface designs, i.e., Miniscal, hinge, etc.
The radii of two articulating bearing surface configurations are desirably selected and matched, taking into account the material from which the surfaces are formed, to minimize contact stress during articulation.
For example, in the embodiment illustrated in
Alternatively, a Miniscal bearing design could be employed, utilizing a conformal curved surface as one artificial facet joint structure, with the bearing side of the opposed artificial facet joint structure having an essentially flat surface. A hemiarthroplasty design could also alternatively be employed, in which one surface of the opposing surfaces does not incorporate the use of an artificial facet joint structure.
In another arrangement, one surface of an artificial facet joint structure can have bearing articulation on both sides of the component and have opposing articulation with a receiving artificial facet joint structure with having opposing mating bearing surfaces.
A variety of materials are suitable for the artificial facet joint structures. Ceramic or ceramic in opposition with a chrome alloy can be used. Suitable stainless steel, including 3161, or titanium alloys, with or without the use of surface hardening and overlay, or hard surface coatings, including zirconia and alumina, can also be employed. The metal surfaces can be made from cast, wrought, hot-forged, or powder-metal consolidated sintered materials. Any of these metals or combination of metals and ceramics can be used in articulation with each other: Biocompatible polymers, e.g., polyethylene, can also be used in articulation with the metals, ceramic, and surface-hardened metals just described. Ultra High Molecular Weight Polyethylene can further be gamma-irradiated, as-molded or as-machined.
The radii of articulating artificial facet joint structures are desirably closely matched to provide contact stress values less than a given threshold value. The desired contact stress value changes with the material employed.
For example, the contact stress value for metal-to-metal bearing combinations is desirably less than about 25,000 psi, and preferably less than 12,000 psi. For polymer surfaces bearing against a metal, ceramic, or surface-hardened metal counter bearing surface, the contact stress value is desirably less than 10,000 psi, and preferably less than 5,000 psi.
For a given material to achieve a desired contact stress value less than the threshold value, the appropriate radii must be chosen. Thus, the radii chosen will change as material changes.
III. REPRESENTATIVE EMBODIMENTSA. Cooperating Caphalad and Caudal Prostheses
FIGS. 20 to 24 show a representative embodiment of a cephalad prosthesis 36 that embody features previously described.
The prosthesis 36 comprises right and left arm components 44 joined to a chimney 42 in a single-piece, unitary construction. Each arm 44 includes an artificial facet joint structure 40 (right and left). As best seen in
In the illustrated embodiment (see
FIGS. 25 to 29 show a representative embodiment of a caudal prosthesis 38 that embody features previously described and that is intended to be used in articulation with the cephalad prosthesis 36 shown in FIGS. 22 to 24. FIGS. 31 to 34 show the caudal prosthesis 38 in articulation with the cephalad prosthesis 36.
The prosthesis 38 includes a pair of artificial facet joint structures 54 (right and left). Each artificial facet structure element 54 includes a convex surface 68, forming hemaspherical-like bearing surface. The surfaces 68 are intended, in use, to articulate with the socket-shaped bearing surfaces 40 on the cephalad prosthesis 36 (see
In the illustrated embodiment, the openings 56 are vertically-elongated, thereby permitting adjustment of the prosthesis 38 to create a desired interpedicle distance. The vertical openings 50 and 56 on the prostheses 36 and 38 permit each prosthesis 36 and 38 to be independently adjusted to create a desired interpedicle distance.
As
B. Total Facet Replacement Using the Cephalad and Caudal Prostheses
With reference now principally to FIGS. 35 to 38, both the superior and inferior portions of the natural facet joint 32 are removed and replaced by the cephalad prosthesis 36 and the caudal prosthesis 38. More particularly, the inferior lamina 20 and the inferior portion of the natural facet joint 32 (e.g., the articulated inferior processes 28 and its supporting bone of the vertebral body 14 above the facet joint) is removed. The lamina may additionally be cut for a wide decompressive laminectomy along a decompressive superior-to-inferior resection line on one or both sides of the vertebral body. The removed natural anatomy is replaced with the cephalad prosthesis 36. The superior portion of the natural facet joint 32 (e.g., the articulated superior process 26 and its supporting bone of the targeted vertebral body 14) is also removed. Desirably, the mamillary process, the accessory process, a portion of the transverse process, and a portion of the pedicle is removed by being rongeured or reamed. The removed natural anatomy is replaced with the caudal prosthesis 38.
In one embodiment, a surgical procedure exposes the spinous process 22, lamina 20, and facet joints 32 at a desired level of the spine 10 using any method common to those of skill in the medical arts.
The inferior portion of the facet joint 32 is cut at or near a selected resection line. Most of the lamina 20 is desirably preserved, as is the facet joint capsule, which may be opened and folded back. The facet joint capsule may be cut perpendicular to its direction. The natural inferior portion of the facet joint 32 may then be retracted from the superior portion. Once the inferior and superior portions of the facet joint are separated, the cut inferior bone, e.g., the inferior articular process 28 and its supporting bone, of the upper joint (e.g., the cut inferior portion of the L4 vertebra in the L4-L5 joint) may be removed, as depicted by phantom lines in
Prominent bone of the superior portion of the natural facet joint, e.g., the superior articular process 26 and its supporting bone, may be also removed, as depicted by phantom lines in
With reference to
With reference now to
As shown in
Because both the superior and inferior portions of the natural facet joint 32 and surrounding bone structures have been removed, the artificial facet joint structures 40/54 of the cephalad prosthesis 36 and the caudal prosthesis 38 can be installed in desired positions and orientations, free of anatomic constraints imposed by the preexisting articular configuration of either the inferior or superior portions of the natural facet joint 32. Furthermore, the artificial facet joint structures 40/54 of the cephalad prosthesis 36 and caudal prosthesis 38 can create an artificial articular configuration that is unlike the pre-existing natural articular configuration in terms of, e.g., interpedicle distance, lardotic angle, and contact stress, so that a desired articulation or bony anatomy can be totally restored. At the same time a desired bone anatomy is restored, decompression of the adjacent nerve root can be maintained to eliminate pain.
Further details of surgical procedures suitable for installing the prostheses are described in co-pending U.S. patent application Ser. No. 09/693,272, filed Oct. 20, 2000, and entitled “Facet Arthroplasty Devices and Methods,” which is incorporated herein by reference.
The above described embodiments of this invention are merely descriptive of its principles and are not to be limited. The scope of this invention instead shall be determined from the scope of the following claims, including their equivalents.
Claims
1. A multi-level spinal stabilization system, comprising: at least two X-shaped members, each X-shaped member having a central member with a superior pair of arms extending from opposed lateral sides thereof and an inferior pair of arms extending from the opposed lateral sides thereof, the superior pair of arms of a first X-shaped member being coupled to an inferior pair of arms of a second X-shaped member.
2. The multi-level spinal stabilization system of claim 1, wherein the at least two X-shaped members are of a unitary construction.
3. The multi-level spinal stabilization system of claim 2, wherein the at least two X-shaped members are formed from an elastomeric material having multiple durometers.
4. The multi-level spinal stabilization system of claim 2, wherein at least a portion of the at least two X-shaped members are formed from a polymeric material.
5. The multi-level spinal stabilization system of claim 1, further comprising first and second connectors adapted to couple the superior pair of arms of the first X-shaped member to the inferior pair of arms of the second X-shaped member.
6. The multi-level spinal stabilization system of claim 5, wherein the first and second connectors each comprise first and second plates pivotally coupled to one another, each plate being adapted to engage a terminal end of one arm of the superior and inferior pair of arms.
7. A multi-level spinal stabilization system, comprising: at least two X-shaped portions having a unitary configuration, each X-shaped portion having a central spacer adapted to be positioned between posterior elements of adjacent vertebrae, and first and second pairs of arms adapted to couple to adjacent vertebrae.
8. The device of claim 7, wherein the X-shaped portions are formed form an elastomeric material have multiple durometers.
9. The device of claim 8, wherein the at least two X-shaped portions, when coupled to adjacent vertebrae, are adapted to provide resistance to movement of the adjacent vertebrae.
10. A method for stabilizing multiple adjacent vertebrae; positioning a central spacer of a first X-shaped member between posterior elements of a first vertebra and an adjacent second vertebra;
- coupling opposed superior arms of the first X-shaped member to the first vertebra; coupling opposed inferior arms of the first X-shaped member to the second vertebra; positioning a central spacer of a second X-shaped member between posterior elements of the second vertebra and an adjacent third vertebra, the second X-shaped member having opposed superior arms that are coupled to the opposed inferior arms of the first X-shaped member; and coupling opposed inferior arms of the second X-shaped member to the third vertebra.
11. The method of claim 10, wherein the opposed superior arms of the second X-shaped member are coupled to the opposed inferior arms of the first X-shaped member by a connector.
12. The method of claim 10, wherein the first and second X-shaped members are of a unitary construction.
13. The method of claim 10, wherein the first and second X-shaped members are formed from an elastomeric material having multiple durometers.
14. A method for stabilizing multiple adjacent vertebrae, comprising: coupling an implant to a posterior portion of at least three adjacent vertebrae, the implant having a unitary configuration and being formed from an elastomeric material with multiple durometers, and the implant being adapted to provide resistance to movement of the at least three adjacent vertebrae.
15. The method of claim 14, wherein the implant includes at least two central spacers, each central spacer being disposed between posterior elements of two adjacent vertebrae and adapted to limit extension of the adjacent vertebrae.
16. The method of claim 14, wherein each central spacer includes a plurality of arms extending therefrom, and wherein the central spacers are connected to one another by the arms.
17. The method of claim 14, wherein the implant comprises a plurality of X-shaped members coupled to one another.
Type: Application
Filed: Dec 14, 2007
Publication Date: Apr 24, 2008
Inventors: Mark Reiley (Piedmont, CA), Robert Scribner (Niwot, CO), James Davidson (Irvine, CA)
Application Number: 11/957,290
International Classification: A61B 17/58 (20060101); A61B 17/56 (20060101);