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. A pair of fixation elements are adapted to be secured within a vertebra in an orientation that best assures a secure and durable attachment to cortical and/or cancellous bone. Artificial facet joint surfaces are mounted on the fixation elements, either directly or with the aid of a support. The artificial facet joint structure may be carried by an arm. The artificial facet joint structure is adapted for articulation with a complementary natural or artificial facet joint structure. Bilateral prostheses may by coupled by a brace to further secure and stabilize the prostheses.
This application is a continuation of U.S. patent application Ser. No. 10/974,009, filed Oct. 25, 2004 which is a continuation-in-part of U.S. patent 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,” which is a continuation-in-part of U.S. patent application Ser. No. 10/067,137, filed Feb. 4, 2002, (now U.S. Pat. No. 6,811,567) entitled “Facet Arthroplasty Devices and Methods,” which is a continuation-in-part of U.S. patent application Ser. No. 09/693,272, filed Oct. 20, 2000, (now U.S. Pat. No. 6,610,091) entitled “Facet Arthroplasty Devices and Methods,” which claims the benefit of Provisional Patent Application Ser. No. 60/160,891, filed Oct. 22, 1999, and entitled “Facet Arthroplasty Devices and Methods,” all of which are 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 INVENTION I. Vertebral AnatomyAs
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 spinous 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 upward, while the inferior articular facet 31 faces downward. As
The facet joint 32 is composed of a superior facet and an inferior facet. The superior facet is formed by the vertebral level below the joint 32, and the inferior facet is formed by the vertebral level above the joint 32. For example, in the L4-L5 facet joint, the superior facet 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 facet 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
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 and/or soft tissues of the spine 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, T11-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 facet and an inferior facet. In anatomical terms, the superior facet 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 facet 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 facet) will be called a “caudal” prosthesis. Likewise, a prosthesis that, in use, replaces the cephalad portion of a facet joint (i.e., the inferior facet) 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). A pair of fixation elements are adapted to be secured within the vertebral body in an orientation that best assures a secure and durable attachment to cortical and/or cancellous bone. Artificial facet joint structures mounted on the fixation elements. In one embodiment, the artificial facet joint structure is mounted on the fixation element by use of a support. The artificial facet joint structures articulate with a complementary natural or artificial facet joint structure. The artificial facet joint structures may by coupled by a brace to further secure and stabilize the prosthesis.
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. Right and left fixation elements are secured within the vertebral body, e.g., to right and left pedicles respectively. An artificial facet joint structure is mounted on each fixation elements. A brace may be coupled to each of the artificial facet joint structures to stabilize the prosthesis.
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). A pair of fixation elements are adapted to be secured within the vertebral body in an orientation that best assures a secure and durable attachment to cortical and/or cancellous bone. In a preferred embodiment, arms are adapted to be mounted on the fixation elements (e.g., using a brace and/or support). The arms carry an artificial facet joint structure for articulation with a complementary natural or artificial facet joint structure. The arms may by coupled by a brace to further secure and stabilize the prosthesis.
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. In one embodiment, right and left fixation elements are secured within the vertebral body, e.g., to the right and left pedicles respectively. A support is mounted on each fixation element. A brace carrying right and left arms (carrying the artificial facet joint structures) is coupled to the supports.
In an alternative embodiment, right and left fixation elements are secured within the vertebral body, e.g., to the right and left pedicles respectively. A support is mounted on each fixation element. An arm, carrying an artificial facet joint structure, is mounted on each support. A brace may be coupled to each of the arms to stabilize the prosthesis.
Another aspect of the invention provides a facet joint prosthesis to replace, on a vertebral body, a caudal portion of a natural facet joint, including: a support component adapted to span a portion of the vertebral body and to support prosthetic caudal facet elements; and a pair of prosthetic caudal facet elements adjustable relative to the support component and adapted to replace the caudal portion of the natural facet joint.
Yet another aspect of the invention provides a prosthesis for replacing a natural spinal facet joint including: a pair of prosthetic caudal facet elements configured to replace the caudal portion of the natural facet joint; and a modular cephalad prosthesis configured to articulate with the caudal facet elements, the modular cephalad prosthesis comprising a pair of arms, a pair of supports, and a brace extending between the arms and the supports, each of the supports having an articulating portion adapted to articulate with the caudal facet elements.
Still another aspect of the invention provides a prosthesis for replacing a natural spinal facet joint comprising: a modular caudal prosthesis comprising a pair of prosthetic caudal facet elements configured to replace the caudal portion of the natural facet joint and a caudal brace extending between the caudal facet elements; and a modular cephalad prosthesis configured to articulate with the caudal facet elements, the modular cephalad prosthesis comprising a pair of arms, a pair of supports, and a cephalad brace extending between the arms and the supports, each of the supports having an articulating portion adapted to articulate with the caudal facet elements.
Other features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended Claims.
INCORPORATION BY REFERENCEAll publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
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 DESCRIPTION OF THE INVENTIONAlthough 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 structures. 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 ProsthesesThe cephalad 36 prosthesis is sized and configured for replacement of the natural inferior facet of a facet joint 32 following removal of the natural inferior facet of the facet joint 32. The caudal prostheses 38 are sized and configured for replacement of the natural superior facet of a facet joint 32 following removal of the natural superior facet of the facet joint 32.
As best shown in
The cephalad 36 prosthesis shown in
The artificial facet joint structures 40 articulate with the superior facet of the facet joint 32. The superior facet 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 14 below the facet joint 32). Desirably, however, the superior facet comprises an artificial facet joint structure 42 formed by a caudal joint replacement prosthesis 38.
The cephalad prosthesis 36 is a modular unit comprising a pair of fixation elements 44 (left and right), a pair of supports 46 (left and right), a pair of arms 48 (left and right), and a brace 50. The modular unit allows assembly of the components in situ on a vertebra. 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.
The left and right fixation elements 44 are fixed to the left and right pedicles 16 respectively, in a position that desirably best assures their fixation to cortical and/or cancellous bone. In the illustrated embodiment, the fixation elements 44 take the form of pedicle screws or nails. The fixation elements 44 are adapted to extend into the right and left pedicles 16 of the vertebral body and serve to anchor the prosthesis 36 in place in an orientation that best assures a secure and durable attachment to bone.
The supports 46 each carry at least one opening 52 sized and configured to accommodate passage of a fixation element 44 to permit mounting of a support 46 on the fixation element 44. The supports 46 are thereby placed on the vertebra 12 in a position dictated by the placement and orientation of the fixation elements 44.
The supports 46 also each have an opening 54 to permit passage of the brace 50. In the illustrated embodiment, the brace 50 takes the form of a transverse rod. Similar to the 46 supports, the left and right cephalad arms 48 have openings 56 to permit passage of the brace 50. The brace 50 is sized to extend across the laminae 20 of a vertebral body 14 and passes through the support openings 54 and the arm openings 56 to hold the supports 46 and arms 48 to thereby stabilize the prosthesis 36.
Each arm 48 carries an artificial facet joint structure 40 for repairing/replacing the inferior facet of a natural facet joint 32. The position of the arms 48 may be adjusted along the brace 50 to bring the artificial facet joint structures 40 of the cephalad prosthesis 36 in articulating configuration with the natural superior facet of the facet joint 32 or an artificial facet joint structure 42 formed by a caudal joint replacement prosthesis 38. The arms 48 can then be secured by locking pins 58 or other suitable mechanism in a desired position.
B. The Caudal ProsthesisThe caudal prostheses 38 shown in
In use, the artificial facet joint structure 42 articulates with the inferior facet of the facet joint 32. The inferior facet can comprise the natural inferior portions of the facet joint 32 (i.e., the natural inferior articular surfaces 28 and supporting bony structure on the vertebral body 14 above the facet joint 32). Desirably, however, the inferior facet comprises an artificial facet joint structure 40 formed by a cephalad joint replacement prosthesis 36, as previously described.
Each prosthesis 38 comprises an artificial facet joint structure 42 and a fixation element 62. Desirably, as
Each artificial facet joint structure 42 has at least one opening 64 sized and configured to accommodate passage of a fixation element 62 to permit mounting of the artificial facet joint structure 42 on a fixation element 62. The artificial facet joint structures 42 are thereby placed on the vertebra 12 in a position dictated by the placement and orientation of the fixation elements 62.
The artificial facet joint structures 42 articulate with the natural inferior facet portion of the facet joint 32 or an artificial facet joint structure 40 formed by a cephalad joint replacement prosthesis 36, as previously described.
The caudal prostheses 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.
C. Artificial Facet Structure ConfigurationIn the prostheses 36 and 38, each artificial facet joint structure 40 and 42 creates a bearing surface having a configuration that facilitates articulation with the bearing surface of another artificial facet joint structure 40 or 42. The particular geometry for the bearing surface configuration for a given artificial facet joint structure 40 and 42 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. The features of the two bearing surfaces (as well as the various other features of the facet joint structures) may also be chosen, if desired, to duplicate the natural articulation of the natural facet joint. Alternatively, the features of the two bearing surfaces (as well as the various other features of the facet joint structures) can be chosen to permit the treated motion segment to experience a lesser or greater degree of articulation than that allowed by the natural motion segment.
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 40 or 42, with the bearing side of the opposed artificial facet joint structure 40 or 42 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 40 or 42.
In another arrangement, one surface of an artificial facet joint structure 40 or 42 can have bearing articulation on both sides of the component and have opposing articulation with a receiving artificial facet joint structure 40 or 42 having opposing mating bearing surfaces.
A variety of materials are suitable for the artificial facet joint structures. 40 and 42. 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 40 and 42 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 is desirably chosen. Thus, the desired radii may change as material changes.
D. Total Facet Replacement Using the Cephalad and Caudal ProsthesesAs best shown in reference to
A portion of the spinous process 22 of the superior vertebra 12 is desirably removed, as depicted by phantom lines in
Prominent bone of the superior facet of the natural facet joint 32, e.g., the superior articular process 26 and its supporting bone, may be also removed, as also depicted by phantom lines in
With reference to
As
The caudal artificial facet joint structures 42 are then mounted on the caudal fixation elements 62 and the fixation elements 62 are then placed in a desired position on the pedicles 16 (with one fixation element 62 on each of the right and left pedicles 16) and screwed securely into the inferior vertebral body, as shown in
With reference to
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.
II. First Alternative Embodiment 1. Cephalad ProsthesisThe left and right fixation elements 74 are fixed to the left and right pedicles 16 respectively, in a position that best assures their fixation to cortical and/or cancellous bone. In the illustrated embodiment, the fixation elements 74 take the form of pedicle screws or nails. The fixation elements 74 are adapted to extend into the right and left pedicles 16 of the vertebral body 14 and serve to anchor the prosthesis 70 in place in an orientation that best assures a secure and durable attachment to bone.
The fixation elements 74 have a threaded body 82 configured to screw into the pedicle 16. A spacing collar 84 may be provided to add additional length to the fixation element 74 if necessary to assure its fixation in the vertebra 12. A nut 86 may be provided to couple with a wrench or other tool to facilitate screwing the fixation element 74 into the vertebra 12. An end portion 88 passes through an opening 90 in the support 76 and permits attachment of the support 76 to be secured by nut 92 or other fixation means, e.g., by threaded engagement.
With reference back to
The transverse brace 80 comprises a right component 104 and a left component 106. An end opening 108 in each of the components 104 and 106 receives a fixation element 102 to fix the right and left components 104 and 106 to the right and left arms 78 respectively, e.g., by threaded engagement. Each component 104 and 106 desirably has a medial opening 110. The medial openings 110 are sized and configured to overlap and permit passage of a fixation element 112, which may be secured by nut 114 or similar mechanism, to thereby couple the components 104 and 106 together to form the transverse brace 80. Similar to brace 50 described in relation to the previous embodiment, the brace 80 extends across the laminae 20 of a vertebral body 14, providing a width-adjustable load-bearing support that further stabilizes the prosthesis 70.
2. Caudal ProsthesisWith continued reference to
The left and right fixation elements 118 are fixed to the left and right pedicles 16 respectively, in a position that best assures their fixation to cortical and/or cancellous bone. In the illustrated embodiment, the fixation elements 118 take the form of pedicle screws or nails. The fixation elements 118 are adapted to extend into the right and left pedicles 16 of the vertebral body 14 and serve to anchor the prosthesis 72 in place in an orientation that best assures a secure and durable attachment to bone.
The fixation elements 118 have a threaded body 124 configured to screw into the pedicle 16. A nut 126 may be provided to couple with a wrench or other tool to facilitate screwing the fixation element 118 into the vertebra 12. An end portion 128 is configured to couple with a support 120, e.g., may be tapered to couple with the support 120 by Morse taper.
Turning back to
In the illustrated embodiment, the brace 122 takes the form of a transverse bar. The brace 122 desirably has right and left end openings 134 that receive fixation elements 136 for attachment to the right and left supports 122 respectively, e.g., by threaded engagement. The brace 122 extends across the laminae 20 of the inferior vertebra 12 to provide a width-adjustable load-bearing support to further stabilize the caudal prosthesis 72.
3. Total Facet Replacement Using the Cephalad and Caudal ProsthesesIn a surgical procedure for total facet replacement using the cephalad and caudal prostheses 70 and 72, the spinous process 22 along with the inferior articular process 28 and its supporting bone, of the upper half of the joint 32 (e.g., the cut inferior facet of the L4 vertebra in the L4-L5 joint) may be removed, as previously described (see
As shown in
A cephalad support 76 is then mounted on each of the fixation elements 74 and secured with a nut 92 or other suitable means, as seen in
Referring now to
As seen in
Each arm 78 of the cephalad prosthesis 138 includes a slot 142 for receiving a brace 144. In the illustrated embodiment, the brace 144 takes the form of a curvilinear transverse rod. The brace 144 is secured to the arms 78 by fixation elements 146.
Similar to the cephalad prosthesis 138, each support 120 of the caudal prosthesis 140 has a slot 148 for receiving a brace 150. In the illustrated embodiment, the brace 150 takes the form of a curvilinear transverse rod. The brace 150 is secured to the supports 120 by fixation elements 152.
The prostheses 138 and 140 are secured in the vertebrae by surgical procedure, as previously described (see also
Similar to the previous embodiments, the cephalad prosthesis 154 is a modular unit comprising a fixation element 158, a support 160, and an arm 162 carrying an artificial facet joint structure 176 that allow assembly of the components in situ. A pair of fixation elements 158 (right and left) are desirably provided and sized and configured to be are secured to the right and left pedicles 16 in an orientation that provides secure fixation to bone. Components are mounted in situ on the fixation elements 158 that are secured to the pedicle 16 in an orientation that provides secure fixation to bone.
In the illustrated embodiment, each fixation element 158 takes the form of a sleeve 164 and a pedicle screw 166. The sleeve 164 is sized and configured for insertion into a bore 168 that has been reamed into the pedicle 16 (see also
The sleeve 164 can be secured for long-term fixation within the bore 168 by adhesive, e.g., bone cement. Alternatively, the sleeve 164 could incorporate a bony in-growth outer surface to which the surrounding bone could grow and adhere. Desirably, the sleeve 164 would fit tightly within the bore 168, with the distal section of the screw 166 anchored within the cancellous bone, thereby securely anchoring the sleeve mechanically while allowing the surrounding bone to biologically adhere to the outer surface of the sleeve. As another alternative (as shown in
A support 160 and arm 162 are integrally formed with the sleeve 164 or otherwise securely mounted on the sleeve 164. An opening 174 in the sleeve 164 extends through the support 160 and serves to receive the pedicle screw 166, e.g., by screwing the pedicle screw 166 into the sleeve 164. The arm 162 is sized and configured to couple with an artificial facet joint structure 176, e.g., by Morse taper or other suitable mechanism that permits rotation (if desired) of the artificial facet joint structure 176 with respect to the support 160 to enable proper orientation of the artificial facet joint structure 176 with the caudal prosthesis 156. In the arrangement illustrated in
The arm 162 can be of a fixed length. In a representative embodiment, the arm 162 is approximately 1 cm in length. As
Also similar to the previous embodiments, the caudal prosthesis 156 is a modular unit comprising a fixation element 184, a support 186, and an artificial facet joint structure 200 that allow assembly of the components in situ. A pair of fixation elements 184 (right and left) are desirably provided and sized and configured to be secured to the right and left pedicles 16 in an orientation that provides secure fixation to bone. Components are mounted in situ on the fixation elements 184 that are secured to the pedicle 16 in an orientation that provides secure fixation to bone.
In the illustrated embodiment, each fixation element 184 takes the form of a sleeve 190 and a pedicle screw 192, similar to the cephalad prosthesis 154. The sleeve 190 is sized and configured for placement within a bore 168 reamed in bone and can be secured by adhesive or by bony in-growth, as previously described. The sleeve 190 provides an increased surface area of attachment, further securing the attachment of the prosthesis 156 to bone. Desirably, the sleeve 190 includes a plurality of vanes 170 that resist rotation of the sleeve 190 in bone to further secure the sleeve 190 within the vertebra 12, as also previously described.
A support 186 is integrally formed with the sleeve 190 or otherwise securely mounted on the sleeve 190. An opening 194 in the sleeve 190 extends through the support 186 and serves to receive the pedicle screw 192, e.g., by screwing the pedicle screw 192 into the sleeve 190. The support 186 is adapted to couple with the artificial facet joint structure 200. For example, in the illustrated embodiment, the support 186 carries a lip 196 which mates with a complementary lip 198 on the structure 200 to couple the structure with the support 186. The artificial facet joint structure 200 is sized and configured to articulate with the natural inferior facet portion of the facet joint 32 or an artificial facet joint structure 176 carried by the cephalad prosthesis 154 (
In a surgical procedure for total facet replacement using the cephalad and caudal prostheses 154 and 156, some or all of the spinous process 22, along with the inferior articular process 28 and its supporting bone, of the upper half of the joint 32 (e.g., the cut inferior facet of the L4 vertebra in the L4-L5 joint) may be removed, as previously described (see
As shown in
The caudal artificial facet joint structure 200, is then mounted on the caudal support 186, as shown in
As
Next, with reference to
While
Similarly, as seen in
In this arrangement, as shown in
It should be understood that, while the embodiments disclosed herein generally describe the complete repair/replacement of a pair of natural facet joints, the teachings of the present invention could be equally applicable to the repair/replacement of a single facet joint, or even the repair/replacement of a single cephalad or caudal portion of a single facet joint, or any combination thereof.
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. An implant for stabilizing the spine, comprising:
- a first member adapted to rigidly couple to a first vertebra and having a lumen extending therethrough;
- a second member adapted to movably couple to a second vertebra, the second member being slidably disposed through and movable relative to the first member;
- wherein the first and second members are adapted to control movement of first and second vertebrae coupled thereto.
2. The implant of claim 1, wherein the first member comprises a first lateral portion having a lumen extending therethrough, a second lateral portion having a lumen extending therethrough, and a connecting member extending between and coupled to the first and second lateral portions.
3. The implant of claim 2, wherein the second member comprises a first pin member slidably disposed through the first lateral portion, and a second pin member slidably disposed through the second lateral portion.
4. The implant of claim 3, wherein the first pin member includes a head formed on a first terminal end thereof and adapted to be received within a portion of the lumen in the first lateral portion, and wherein the second pin member includes a head formed on a first terminal end thereof and adapted to be received within a portion of the lumen in the second lateral portion.
5. The implant of claim 4, wherein the lumens in the first and second lateral portions each include stop formed therein and adapted to limit slidably movement of the head of the pin member.
6. The implant of claim 4, wherein a second terminal end of each of the first and second pin members includes a spherical member formed thereon and adapted to be rotatably coupled to a fastening element for movably coupling the first and second pin members to a second vertebra.
7. The implant of claim 2, wherein the connecting member comprises an elongate bar having opposed terminal ends that are adapted to mate to the first and second lateral portions.
8. An implant for stabilizing the spine, comprising:
- a first member having a first portion adapted to rigidly couple to a first vertebra, and a second portion slidably movable with respect to the first portion and adapted to couple to a second vertebra;
- a second member having a first portion adapted to rigidly couple to a first vertebra, and a second portion slidably movable with respect to the first portion and adapted to couple to a second vertebra;
- and a connecting member extending between and coupled to the first and second members.
9. The implant of claim 8, wherein the second portion of each of the first and second members comprises a pin member that is slidably disposed through the first portion.
10. The implant of claim 9, wherein each pin member includes a head that is adapted to be received within a lumen formed in the first portion of each of the first and second members, and wherein each lumen includes an enlarged diameter region adapted to receive the head of the pin member.
11. The implant of claim 8, wherein the first portion of each of the first and second members includes an offset connector formed thereon and adapted to mate to the connecting member.
Type: Application
Filed: Nov 30, 2007
Publication Date: Jun 5, 2008
Inventors: Mark A. Reiley (Piedmont, CA), Robert M. Scribner (Niwot, CO), Lawrence R. Jones (Conifer, CO), David Stinson (Woodinville, WA)
Application Number: 11/948,963
International Classification: A61B 17/58 (20060101); A61F 2/44 (20060101); A61B 17/56 (20060101);