Method and apparatus for spine joint replacement

A prosthesis for the replacement of the cartilaginous structures of a spine motion segment is described. The prosthesis comprises an intervertebral disc prosthesis in combination with a facet joint prosthesis.

FIELD OF THE INVENTION

This invention relates to surgical devices and methods in general, and more particularly to surgical devices and methods for replacing a damaged, diseased, or otherwise painful spinal joint.

BACKGROUND OF THE INVENTION

Traumatic, inflammatory, metabolic, synovial, neoplastic and degenerative disorders of the spine can produce debilitating pain that can have severe socioeconomic and psychological effects.

One of the most common surgical interventions today is arthrodesis, or spine fusion, in which two or more adjacent vertebral bodies are fused together in order to alleviate pain associated with the disc(s) located between those vertebral bodies. Approximately 300,000 such procedures are performed annually in the U.S. alone. Clinical success varies considerably, depending upon technique and indications, and consideration must be given to the concomitant risks and complications.

For example, while spine fusion generally helps to eliminate certain types of pain, it has also been shown to decrease function by limiting the range of motion for patients in flexion, extension, rotation and lateral bending. Furthermore, it is believed that spine fusion creates increased stresses on (and, therefore, accelerated degeneration of) adjacent non-fused motion segments. Additionally, pseudoarthrosis, resulting from an incomplete or ineffective fusion, may reduce or even totally eliminate the desired pain relief for the patient. Also, the fusion device(s) used to effect fusion, whether artificial or biological, may migrate out of the fusion site, thereby creating significant new problems for the patient.

Recently, attempts have been made to recreate the natural biomechanics of the spine through the use of an artificial disc. Artificial discs are intended to restore articulation between vertebral bodies so as to recreate the full range of motion normally allowed by the elastic properties of the natural disc, which directly connects two opposing vertebral bodies. Various artificial discs are described by Stefee et al. in U.S. Pat. No. 5,071,437; Gill et al. in U.S. Pat. No. 6,113,637; Bryan et al. in U.S. Pat. No. 6,001,130; Hedman et al. in U.S. Pat. No. 4,759,769; Ray in U.S. Pat. No. 5,527,312; Ray et al. in U.S. Pat. No. 5,824,093; Buttner-Janz in U.S. Pat. No. 5,401,269; and Serhan et al. in U.S. Pat. No. 5,824,094; all which documents are hereby incorporated herein by reference. Still other artificial discs are known in the art.

Unfortunately, however, artificial discs alone do not adequately address all of the mechanics of the motion of the spinal column.

In addition to the intervertebral disc, posterior elements called the facet joints help to support axial, torsional and shear loads that act on the spinal column. Furthermore, the facet joints are diarthroidal joints that provide both sliding articulation and load transmission features. However, the facet joints can also be a significant source of spinal disorders and, in many cases, debilitating pain. For example, a patient may suffer from arthritic facet joints, severe facet joint tropism or otherwise deformed facet joints, facet joint injuries, etc. There is currently a lack of good interventions for facet joint disorders. Facetectomy, or the removal of the facet joints, may provide some relief, but it is also believed to produce significant decreases in the stiffness of the spinal column (i.e., hypermobility) in all planes of motion: flexion and extension, lateral bending, and rotation. Furthermore, problems with the facet joints can also complicate treatments associated with other portions of the spine. By way of example, contraindications for artificial discs include arthritic facet joints, absent facet joints, severe facet joint tropism or otherwise deformed facet joints.

A superior vertebra with its inferior facets, an inferior vertebra with its superior facets, the intervertebral disc, and seven spinal ligaments together comprise a spinal motion segment or functional spine unit. The spinal motion segment provides complex motion along three orthogonal axes, both in rotation (lateral bending, flexion and extension, and axial rotation) and in translation (anterior-posterior, medial-lateral, and cranial-caudal). Furthermore, the spinal motion segment provides physiological limits and stiffnesses in each rotational and translational direction to create a stable and strong column structure to support physiological loads.

As mentioned above, compromised facet joints are a contraindication for disc replacement, due to the inability of the artificial disc (when used with compromised facet joints, or when used with missing facet joints) to properly restore the natural biomechanics of the spinal motion segment. It would therefore be an improvement in the art to provide a spine implant system that facilitates concurrent replacement of the intervertebral disc and facet joints where both have been compromised due to disease or trauma.

U.S. Pat. No. Re. 36,758 (Fitz) discloses an artificial facet joint where the inferior facet, the mating superior facet, or both, are covered with a cap. This cap requires no preparation of the bone or articular surfaces; it covers and, therefore, preserves the bony and articular structure. The capping of the facet has several potential disadvantages, however. If the facet joint is osteoarthritic, a cap will not remove the source of the pain. Additionally, at least in the case of surface replacements for osteoarthritic femoral heads, the capping of articular bone ends has proven to lead to clinical failure by means of mechanical loosening. This clinical failure is hypothesized to be a sequela of disrupting the periosteum and ligamentum teres femoris, both serving a nutrition delivery role to the femoral head, thereby leading to avascular necrosis of the bony support structure for the surface replacement. It is possible that corresponding problems could develop from capping the facet. Another potential disadvantage of facet capping is that in order to accommodate the wide variability in anatomical morphology of the facets, not only between individuals but also between levels within the spinal column, a very wide range of cap sizes and shapes is required.

U.S. Pat. No. 6,132,464 (Martin) discloses a spinal facet joint prosthesis that is supported on the lamina (which is sometimes also referred to as the posterior arch). Extending from this support structure are inferior and/or superior blades that replace the cartilage at the facet joint. Like the design of the aforementioned U.S. Pat. No. Re. 36,758, the prosthesis of U.S. Pat. No. 6,132,464 generally preserves existing bony structures and therefore does not address pathologies which affect the bone of the facets in addition to affecting the associated cartilage. Furthermore, the prosthesis of U.S. Pat. No. 6,132,464 requires a secure mating between the prosthesis and the lamina. However, the lamina is a very complex and highly variable anatomical surface. As a result, in practice, it is very difficult to design a prosthesis that provides reproducible positioning against the lamina so as to correctly locate the cartilage-replacing blades for the facet joints.

Another approach to surgical intervention for spinal facets is disclosed in International Patent Publication No. WO9848717A1 (Villaret et al.). While this publication teaches the replacement of spinal facets, the replacement is interlocked in a manner so as to immobilize the joint.

Thus it will be seen that previous attempts to provide facet joint replacement have proven inadequate.

In some circumstances, additional structures of a vertebra beside the facets may have been compromised by disease or trauma. For example, the lamina, the spinous process and/or the two transverse processes may have been compromised by disease or trauma. In such a circumstance, it would be useful to have a prosthesis which would allow the replacement of the same.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a spine joint reconstruction assembly that replaces the intervertebral disc and one or more of the facet joints in order to restore the natural biomechanics of a spinal motion segment.

Another object of the present invention is to provide a method for reconstructing the spine joint by replacing the intervertebral disc and one or more of the facet joints in order to restore the natural biomechanics of a spinal motion segment.

Still another object of the present invention is to provide a kit for the reconstruction of multiple spine joints to replace intervertebral discs and facet joints in order to restore the natural biomechanics of a spinal motion segment.

In accordance with the present invention, the preferred embodiment, the intervertebral disc is excised and replaced with an artificial disc. This artificial disc may be a device such as is described by Stefee et al. in U.S. Pat. No. 5,071,437; Gill et al. in U.S. Pat. No. 6,113,637; Bryan et al. in U.S. Pat. No. 6,001,130; Hedman et al. in U.S. Pat. No. 4,759,769; Ray in U.S. Pat. No. 5,527,312; Ray et al. in U.S. Pat. No. 5,824,093; Buttner-Janz in U.S. Pat. No. 5,401,269; and Serhan et al. in U.S. Pat. No. 5,824,094; all which documents are hereby incorporated herein by reference. Alternatively, the artificial disc may be some other artificial disc of the sort known in the art.

In addition to replacing the intervertebral disc, at least one of the facet joints is replaced in accordance with the apparatus and methods described hereinafter. Alternatively, the facet joints may be replaced as described by Fitz in U.S. Pat. No. Re. 36,758; Martin in U.S. Pat. No. 6,132,464; and/or Villaret et al. in International Patent Publication No. WO 9848717A1, which documents are hereby incorporated herein by reference. Or one or more of the facet joints may be replaced by other apparatus and methods known in the art.

The present invention has several advantages over the prior art. For one thing, the present invention can provide a complete replacement of all of the articulation surfaces of a spine motion segment: the intervertebral disc and the facet joints. Proper disc height is restored while degenerated facet joints and the underlying painful bone is replaced. The prosthetic disc and prosthetic facet joints work together to reproduce the desired physiological range of motion and to provide low friction articulations, so that adjacent motion segments are returned to physiological levels of stress and strain. Furthermore, osteophytic growth can be concurrently removed, and the artificial disc and facet joint prosthesis together reestablish intervertebral and central foraminal spaces to ensure decompression of any nerve structure. Thus, all sources of pain, such as pain associated with osteoarthritis, instability, and nerve compression, are removed while restoring full function of the spine motion segment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Disc Prosthesis and Single Facet Prosthesis

Referring now toFIG. 3, in accordance with one aspect of the present invention, the intervertebral disc2has been replaced by an artificial disc AD. This artificial disc AD may be a device such as is described by Stefee et al. in U.S. Pat. No. 5,071,437; Gill et al. in U.S. Pat. No. 6,113,637; Bryan et al. in U.S. Pat. No. 6,001,130; Hedman et al. in U.S. Pat. No. 4,759,769; Ray in U.S. Pat. No. 5,527,312; Ray et al. in U.S. Pat. No. 5,824,093; Buttner-Janz in U.S. Pat. No. 5,401,269; and Serhan et al. in U.S. Pat. No. 5,824,094; all which documents are hereby incorporated herein by reference. Alternatively, the artificial disc may be some other artificial disc of the sort known in the art.

In addition to the foregoing, the left inferior facet6of vertebra1has been resected and an inferior facet prosthesis4has been attached to vertebra1. Similarly, the left superior facet of vertebra3has been resected and a superior facet prosthesis5has been attached to vertebra3.

FIG. 4illustrates a dorsal view of the elements shown inFIG. 3. It can be appreciated that inferior facet prosthesis4replicates the natural anatomy when compared to the contralateral inferior facet6of vertebra1. Similarly, it can be appreciated that superior facet prosthesis5replicates the natural anatomy when compared to the contralateral superior facet7of vertebra3.

Turning now toFIG. 5, a perspective view of vertebra1with implanted inferior facet prosthesis4is provided. Resection at31has removed the natural inferior facet6at the bony junction between the inferior facet6and the posterior arch35. In this manner, bone pain associated with a disease, such as osteoarthritis, or trauma may be eliminated as the involved bony tissue has been osteotomized.

FIG. 6illustrates a perspective view of inferior facet prosthesis4. Surface8replicates the natural articular surface of the replaced inferior facet6. Post9provides a means to affix inferior facet prosthesis4to vertebra1. Post9is implanted into the interior bone space of the left pedicle P (FIG. 7) on vertebra1and may or may not extend into the vertebral body of vertebra1to provide additional stability.

FIG. 7illustrates a cranial view of vertebra3with implanted superior facet prosthesis5. Resection surface32represents the bony junction between the natural superior facet and the posterior arch35.

FIG. 8illustrates a perspective view of superior facet prosthesis5. Surface36replicates the natural articular surface of the replaced superior facet7. Post37provides a means for affixing superior facet prosthesis5to vertebra3. Post37is implanted into the interior bone space of the left pedicle P (FIG. 7) on vertebra3and may or may not extend into the vertebral body of vertebra3to provide additional stability.

When the total facet joint is replaced, as shown inFIGS. 3 and 4, then surface8(FIG. 6) articulates with surface36(FIG. 8) to recreate the natural biomechanics of the spine motion segment made up of vertebra1, vertebra3, and intervertebral disc2.

FIG. 9illustrates an alternative inferior facet prosthesis10which is implanted into the interior bone space of posterior arch35. The interior bone space is accessed from the resection31.

FIG. 10shows details of alternative inferior facet prosthesis10, including the fin13that extends into the interior bone space of posterior arch35. Surface12replicates the natural articular surface of the replaced facet.

If desired, a corresponding fin construction can be used to form a prosthetic superior facet.

The surfaces of post9(FIG. 6), post37(FIG. 8) and fin13(FIG. 10) may or may not include porous coatings to facilitate bone ingrowth to enhance the long term fixation of the implant. Furthermore, such porous coatings may or may not include osteoinductive or osteoconductive substances to further enhance the bone remodeling into the porous coating.

Referring now toFIG. 11, there is shown a lateral view of a superior vertebra14and an inferior vertebra16, with an intervertebral disc15located in between is shown. The left inferior facet of vertebra14has been resected and an inferior facet prosthesis18has been attached to vertebra14by means of a screw fastener17. Similarly, the left superior facet of vertebra16has been resected and a superior facet prosthesis19has been attached to vertebra16by means of a screw fastener17.

FIG. 12illustrates a dorsal view of the elements ofFIG. 11. It can be appreciated that inferior facet prosthesis18replicates the natural anatomy when compared to the contralateral inferior facet22of vertebra14. Similarly, it can be appreciated that superior facet prosthesis19replicates the natural anatomy when compared to the contralateral superior facet21of vertebra16.

Turning now toFIG. 13, there is provided a perspective view of vertebra14with implanted inferior facet prosthesis18. Resection34has removed the natural inferior facet at the bony junction between the inferior facet and the posterior arch37. In this manner, bone pain associated with a disease, such as osteoarthritis, or trauma may be eliminated inasmuch as the involved bony tissue has been osteotomized.

FIG. 14illustrates a perspective view of inferior facet prosthesis18. Surface23replicates the natural articular surface of the replaced facet. Flange25contacts the pedicle and hole24receives a fastener to attach inferior facet prosthesis18to vertebra14.

FIG. 15illustrates a cranial view of vertebra16with implanted superior facet prosthesis19. Resection surface35represents the bony junction between the natural superior facet and the posterior arch38.

FIG. 16illustrates a perspective view of superior facet prosthesis19. Surface27replicates the natural articular surface of the replaced facet. Flange39contacts the pedicle and hole26receives a fastener to attach inferior facet prosthesis19to vertebra16.

FIG. 17illustrates an alternative superior facet prosthesis40with an bearing surface41that mounts to substrate42. The bearing surface41is a biocompatible polymeric material, such as ultra high molecular weight polyethylene. Alternately, the bearing surface can be ceramic, such as zirconia or alumina, or metal. The substrate is a biocompatible metal alloy, such as an alloy of titanium, cobalt, or iron.

Disc Prosthesis and Double Facet Prosthesis

Referring next toFIG. 18, there is shown a superior vertebra1005and an inferior vertebra1010, with an intervertebral disc1015located in between. Vertebra1005has superior facets1020, inferior facets1025, a lamina (also sometimes referred to as a posterior arch)1030, a spinous process1035, and pedicles1040. Vertebra1010has superior facets1045, inferior facets1050, a posterior arch1055, a spinous process1060, and pedicles1065(only one of which is seen inFIG. 18).

Referring now toFIGS. 19 and 20, in accordance with another aspect of the invention, intervertebral disc1015has been replaced by an artificial disc AD. This artificial disc AD may be a device such as is described by Stefee et al. in U.S. Pat. No. 5,071,437; Gill et al. in U.S. Pat. No. 6,113,637; Bryan et al. in U.S. Pat. No. 6,001,130; Hedman et al. in U.S. Pat. No. 4,759,769; Ray in U.S. Pat. No. 5,527,312; Ray et al. in U.S. Pat. No. 5,824,093; Buttner-Janz in U.S. Pat. No. 5,401,269; and Serhan et al. in U.S. Pat. No. 5,824,094; all which documents are hereby incorporated herein by reference. Alternatively, the artificial disc may be some other artificial disc of the sort known in the art.

In addition to the foregoing, the left and right inferior facets1025of vertebra1005have been resected at1070and a bilateral inferior facet prosthesis1075has been attached to vertebra1005using screw fasteners1080. Similarly, the left and right superior facets1045of vertebra1010have been resected at1082(FIG. 24) and a bilateral superior facet prosthesis1085has been attached to vertebra1010using screw fasteners1090.

InFIG. 20it can be appreciated that bilateral inferior facet prosthesis1075replicates the natural anatomy when compared to the intact inferior facet1025of vertebra1005. Furthermore, bilateral facet prosthesis1075extends from its attachment point in a manner that does not require contact with, or mating to, the complex geometry of the lamina (or posterior arch)1030. Resection surfaces1070provide adequate clearance for bilateral inferior facet prosthesis1075and provide complete removal of the diseased or traumatized natural inferior facets1025.

FIGS. 21 and 22illustrate how the geometry of the bridge1095of bilateral inferior facet prosthesis1075matches that of the posterior arch1030of vertebra1005in order to provide adequate clearance for the central foramen1100. Articular surfaces1105articulate with the opposing superior facets1045(or their prosthetic replacements) of the vertebra1010.

FIG. 23illustrates the bilateral inferior facet prosthesis1075with flanges1110that abut against the pedicles1040of vertebra1005. Bridge1095connects the articular surfaces1105. Holes1115allow the attachment of bilateral inferior facet prosthesis1075to vertebra1005by means of screw fasteners1080. Alternatively, screw fasteners1080could be replaced with staples, pins, tacks, anchors, modular fixation posts, or the like. These alternative fasteners could further include porous coatings to further enhance bony fixation, and could also include osteoconductive or osteoinductive substances.

InFIG. 24it can be appreciated that bilateral superior facet prosthesis1085replicates the natural anatomy when compared to the intact superior facets1045of vertebra1010. Furthermore, bilateral facet prosthesis1085extends from its attachment point in a manner that does not require contact with, or mating to, the complex geometry of the lamina (or posterior arch)1055. Resection surfaces1082provide adequate clearance for bilateral superior facet prosthesis1085and provide complete removal of the diseased or traumatized natural superior facets1045.

FIG. 25illustrates how the geometry of the bridge1120of bilateral superior facet prosthesis1085matches that of the posterior arch1055of vertebra1010in order to provide adequate clearance for the central foramen1125. Articular surfaces1130articulate with the opposing inferior facets of the vertebra1005.

FIG. 27illustrates an alternative superior facet prosthesis1085A with a bearing surface1130A that mounts to substrate1131A. The bearing surface1130A is preferably a biocompatible polymeric material, such as ultra high molecular weight polyethylene. Alternately, the bearing surface1130A can be ceramic, such as zirconia or alumina. The substrate1131A is preferably a biocompatible metal alloy, such as an alloy of titanium, cobalt, or iron.

FIG. 28illustrates a superior vertebra1145, a middle vertebra1150, and an inferior vertebra1155. Superior facet prosthesis1085articulates with quad-facet prosthesis1160to recreate the natural biomechanics of the replaced facet joints. Inferior facet prosthesis1075articulates with quad-facet prosthesis1160to recreate the natural biomechanics of the replaced facet joints at the next upper level. Thus,FIG. 28illustrates a two level reconstruction of facet joints. Superior facet prosthesis1085, quad-facet prosthesis1160, and inferior facet prosthesis1075are each attached to bone by means of screw fasteners1165.

In the lateral view ofFIG. 29, it can be appreciated that superior facet prosthesis1085, quad-facet prosthesis1160, and inferior facet prosthesis1075do not encroach into the intervertebral foraminal spaces1167where nerve roots extend laterally from the spinal cord.

Referring next toFIG. 30, it should be appreciated that superior bridge1170and inferior bridge1175of quad-facet prosthesis1160do not contact any portion of vertebra1150. Mounting holes1180(shown inFIG. 31) are used to secure the flanges1185against the pedicles of vertebra1150.

InFIG. 32, an alternative inferior bilateral facet prosthesis1190is presented. To further stabilize the implant and to counter moments that act upon the two points of fixation into the pedicles, a set of parallel flanges1195extend posteriorly such that the two flanges straddle the spinous process1035. A bolt1200is used to fasten the parallel flanges to the spinous process. Alternatively, other adjunctive structural features could be added to further stabilize the prosthesis. For example, a strut that extends, and attaches, to the transverse process could be used to further stabilize the prosthesis.

Looking next atFIGS. 33 and 34, there is shown a superior and inferior unilateral facet prosthesis1300. Unilateral facet prosthesis1300comprises a body1305and a stem1310extending out of body1305. A superior element1315extends vertically upward from body1305, and an inferior element1320extends vertically downward from body1305. Unilateral facet prosthesis1300is configured so that when its stem1310extends into the pedicle of vertebra1325, superior element1315will replace a resected superior facet, and inferior element1320will replace a resected inferior facet. If desired, stem1310could be replaced with a screw extending through a hole in body1305and into the pedicle.

Disc Prosthesis and Quadruple Facet Prosthesis

Referring next toFIG. 35, there is shown a natural lumbar vertebra2005comprising a natural vertebral body2010, a pair of natural pedicles2015extending from natural vertebral body2010, a natural lamina2020extending from natural pedicles2015, a pair of natural superior facets2025extending from natural pedicles2015and natural lamina2020, a pair of natural inferior facets2030extending from natural lamina2020, a natural spinous process2035extending from natural lamina2020, and a pair of natural transverse processes2040extending from natural pedicles2015.

In accordance with another aspect of the invention, the intervertebral disc on one side or the other of vertebral body2010is replaced by an artificial disc. This artificial disc may be a device such as is described by Stefee et al. in U.S. Pat. No. 5,071,437; Gill et al in U.S. Pat. No. 6,113,637; Bryan et al. in U.S. Pat. No. 6,001,130; Hedman et al. in U.S. Pat. No. 4,759,769; Ray in U.S. Pat. No. 5,527,312; Ray et al. in U.S. Pat. No. 5,824,093; Buttner-Janz in U.S. Pat. No. 5,401,269; and Serhan et al. in U.S. Pat. No. 5,824,094; all which documents are hereby incorporated herein by reference. Alternatively, the artificial disc may be some other artificial disc of the sort known in the art.

In addition to the foregoing, and looking next atFIGS. 36 and 37, there is shown a novel prosthesis2100which is adapted to replace the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035, and the two natural transverse processes2040. To this end, prosthesis2100comprises a pair of prosthetic mounts2115, a prosthetic lamina2120extending from prosthetic mounts2115, a pair of prosthetic superior facets2125extending from prosthetic mounts2115and prosthetic lamina2120, a pair of prosthetic inferior facets2130extending from prosthetic lamina2120, a prosthetic spinous process2135extending from prosthetic lamina2120, and a pair of prosthetic transverse processes2140extending from prosthetic mounts2115.

In the use of prosthesis2100, natural lumbar vertebra2005is resected at its natural pedicles2015so as to remove the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035, and the two natural transverse processes2040, leaving a pair of pedicle end surfaces2041(FIG. 38). Then the prosthesis2100may be attached to the natural pedicles2015, e.g., by placing prosthetic mounts2115against pedicle surfaces2041and then passing screws2145through screw holes2147and into natural pedicles2015, as shown inFIGS. 39–41. As seen in the drawings, the relative size, shape and positioning of the prosthetic lamina2120, the two prosthetic superior facets2125, the two prosthetic inferior facets2130, the prosthetic spinous process2135, and the two prosthetic transverse processes2140essentially mimic the relative size, shape and positioning of the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035, and the two natural transverse processes2040, whereby to effectively restore the vertebra. If desired, holes2150may be provided in the prosthetic spinous process2135and/or the two prosthetic transverse processes2140so as to facilitate re-attaching soft tissue to these structures.

Looking next atFIG. 42, there is shown a novel prosthesis2200which is adapted to replace natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, and natural spinous process2035. To this end, prosthesis2200comprises a pair of prosthetic mounts2215, a prosthetic lamina2220extending from prosthetic mounts2215, a pair of prosthetic superior facets2225extending from prosthetic mounts2215and prosthetic lamina2220, a pair of prosthetic inferior facets2230extending from prosthetic lamina2220, and a prosthetic spinous process2235extending from prosthetic lamina2220.

In the use of prosthesis2200, natural lumbar vertebra2005is resected at its natural pedicles2015so as to remove the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the spinous process2035and the two natural transverse processes2040, leaving a pair of pedicle surfaces2041(FIG. 38). Then the prosthesis2200may be attached to the natural pedicles2015, e.g., by placing prosthetic mounts2215against pedicle surfaces2041and then passing screws2145through holes2247and into natural pedicles2015. As seen in the drawing, the relative size, shape and positioning of prosthetic lamina2220, the two prosthetic superior facets2225, the two prosthetic inferior facets2230, and the prosthetic spinous process2235essentially mimic the relative size, shape and positioning of the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, and the natural spinous process2035, whereby to effectively restore the vertebra. If desired, holes2150may be provided in the prosthetic spinous process2235so as to facilitate re-attaching soft tissue to this structure.

Looking next atFIG. 43, there is shown a novel prosthesis2300which is adapted to replace the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, and the two natural transverse processes2040. To this end, prosthesis2300comprises a pair of prosthetic mounts2315, a prosthetic lamina2320extending from prosthetic mounts2315, a pair of prosthetic superior facets2325extending from prosthetic mounts2315and prosthetic lamina2320, a pair of prosthetic inferior facets2330extending from prosthetic lamina2320, and a pair of prosthetic transverse processes2340extending from prosthetic mounts2315.

In the use of prosthesis2300, natural lumbar vertebra2005is resected at natural pedicles2015so as to remove natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035and the two natural transverse processes2040, leaving a pair of pedicle surfaces2041(FIG. 38). Then the prosthesis2300may be attached to the natural pedicles2015, e.g., by placing prosthetic mounts2315against pedicle surfaces2041and then passing screws2145through holes2347and into natural pedicles2015. As seen in the drawing, the relative size, shape and positioning of the prosthetic lamina2320, the two prosthetic superior facets2325, the two prosthetic inferior facets2330, and the two prosthetic transverse processes2340essentially mimic the relative size, shape and positioning of the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, and the two natural transverse processes2040, whereby to effectively restore the vertebra. If desired, holes2150may be provided in the two prosthetic transverse processes2340so as to facilitate re-attaching soft tissue to these structures.

Looking next atFIG. 44, there is shown a novel prosthesis2400which is adapted to replace the natural lamina2020, the two natural superior facets2025, and the two natural inferior facets2030. To this end, prosthesis2400comprises a pair of prosthetic mounts2415, a prosthetic lamina2420extending from prosthetic mounts2415, a pair of prosthetic superior facets2425extending from prosthetic mounts2415and prosthetic lamina2420, and a pair of prosthetic inferior facets2430extending from prosthetic lamina2420.

In the use of prosthesis2400, natural lumbar vertebra2005is resected at pedicles2015so as to remove the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035, and the two natural transverse processes2040, leaving a pair of pedicle surfaces2041(FIG. 38). Then the prosthesis2400may be attached to the natural pedicles2015, e.g., by placing prosthetic mounts2415against pedicle surfaces2041and then passing screws2145through holes2447and into natural pedicles2015. As seen in the drawing, the relative size, shape and positioning of prosthetic lamina2420, the two prosthetic superior facets2425, and the two prosthetic inferior facets2430essentially mimic the relative size, shape and positioning of the natural lamina2020, the two natural superior facets2025and the two natural inferior facets2030, whereby to effectively restore the vertebra.

Looking next atFIGS. 45–47, there is shown a novel prosthesis2500which is adapted to replace a pair of natural pedicles2015, the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035, and the two natural transverse processes2040. To this end, prosthesis2500comprises a pair of prosthetic pedicles2515, a prosthetic lamina2520extending from prosthetic pedicles2515, a pair of prosthetic superior facets2525extending from prosthetic pedicles2515and prosthetic lamina2520, a pair of prosthetic inferior facets2530extending from prosthetic lamina2520, a prosthetic spinous process2535extending from prosthetic lamina2520, and a pair of prosthetic transverse processes2540extending from prosthetic pedicles2515.

In the use of prosthesis2500, natural lumbar vertebra2005is resected at the bases of natural pedicles2015so as to remove to two natural pedicles2015, the natural lumina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035, and the two natural transverse processes2040, leaving a vertebral body end face2042(FIG. 48). Then the prosthesis2500may be attached to the natural vertebral body2010, e.g., by placing prosthetic pedicles2515against vertebral body end face2042and then passing screws2145through holes2547and into natural vertebral body2010, as shown inFIG. 49. As seen in the drawings, the relative size, shape and positioning of the two prosthetic pedicles2515, the prosthetic lamina2520, the two prosthetic superior facets2525, the two prosthetic inferior facets2530, the prosthetic spinous process2535, and the two prosthetic transverse processes2540essentially mimic the relative size, shape and positioning of the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035, and the two natural transverse processes2040, whereby to effectively restore the vertebra. If desired, holes2150may be provided in prosthetic spinous process2535and the two prosthetic transverse processes2540so as to facilitate re-attaching soft tissue to these structures.

Looking next atFIG. 50, there is shown a novel prosthesis2600which is adapted to replace the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, and the natural spinous process2035. To this end, prosthesis2600comprises a pair of prosthetic pedicles2615, a prosthetic lamina2620extending from prosthetic pedicles2615, a pair of prosthetic superior facets2625extending from prosthetic pedicles2615and prosthetic lamina2620, a pair of prosthetic inferior facets2630extending from prosthetic lamina2620, and a prosthetic spinous process2635extending from prosthetic lamina2620.

In the use of prosthesis2600, natural lumbar vertebra2005is resected at the bases of natural pedicles2015so as to remove the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035and the two natural transverse processes2040, leaving a vertebral body end face2042(FIG. 48). Then the prosthesis2600may be attached to the natural vertebral body2010, e.g., by placing prosthetic pedicles2615against vertebral body end face2042and then passing screws2145through holes2647and into natural vertebral body2010. As seen in the drawing, the relative size, shape and positioning of the two prosthetic pedicles2615, the prosthetic lamina2620, the two prosthetic superior facets2625, the two prosthetic inferior facets2630, and the prosthetic spinous process2635essentially mimic the relative size, shape and positioning of the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, and the natural spinous process2035, whereby to effectively restore the vertebra. If desired, holes2150may be provided in prosthetic spinous process2635so as to facilitate re-attaching soft tissue to this structure.

Looking next atFIG. 51, there is shown a novel prosthesis2700which is adapted to replace the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, and the two natural transverse processes2040. To this end, prosthesis2700comprises a pair of prosthetic pedicles2715, a prosthetic lamina2720extending from prosthetic pedicles2715, a pair of prosthetic superior facets2725extending from prosthetic pedicles2715and prosthetic lamina2720, a pair of prosthetic inferior facets2730extending from prosthetic lamina2720, and a pair of prosthetic transverse processes2740extending from prosthetic pedicles2715.

In the use of prosthesis2700, natural lumbar vertebra2005is resected at the bases of natural pedicles2015so as to remove the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035, and the two natural transverse processes2040, leaving a vertebral body end face2042(FIG. 48). Then the prosthesis2700may be attached to the natural vertebral body2010, e.g., by placing prosthetic pedicles2715against vertebral body end face2042and then passing screws2145through holes2747and into vertebral body2010. As seen in the drawing, the relative size, shape and positioning of the two prosthetic pedicles2715, the prosthetic lamina2720, the two prosthetic superior facets2725, the two prosthetic inferior facets2730, and the two prosthetic transverse processes2740essentially mimic the relative size, shape and positioning of the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, and the two natural transverse processes2040, whereby to effectively restore the vertebra. If desired, holes2150may be provided in the two prosthetic transverse processes2740so as to facilitate re-attaching soft tissue to these structures.

Looking next atFIG. 52, there is shown a novel prosthesis2800which is adapted to replace the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, and the two natural inferior facets2030. To this end, prosthesis2800comprises a pair of prosthetic pedicles2815, a prosthetic lamina2820extending from prosthetic pedicles2815, a pair of prosthetic superior facets2825extending from prosthetic pedicles2815and prosthetic lamina2820, and a pair of prosthetic inferior facets2830extending from prosthetic lamina2820.

In the use of prosthesis2800, natural lumbar vertebra2005is resected at the bases of natural pedicles2015so as to remove the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, the two natural inferior facets2030, the natural spinous process2035, and the two natural transverse processes2040, leaving a vertebral body end face2042(FIG. 48). Then the prosthesis2800may be attached to natural vertebral body2010, e.g., by placing prosthetic pedicles2715against vertebral body end face2042and then passing screws2145through holes2847and into natural vertebral body2010. As seen in the drawing, the relative size, shape and positioning of the two prosthetic pedicles2815, the prosthetic lamina2820, the two prosthetic superior facets2825, and the two prosthetic inferior facets2830essentially mimic the relative size, shape and positioning of the two natural pedicles2015, the natural lamina2020, the two natural superior facets2025, and the two natural inferior facets2030, whereby to effectively restore the vertebra.

It should also be appreciated that prostheses2100,2200,2300,2400,2500,2600,2700and2800may be attached to natural vertebra2005with apparatus other than the screws2145discussed above. Thus, for example, prostheses2100,2200,2300,2400,2500,2600,2700and2800may be attached to natural vertebra2005with rods or posts, etc. See, for example,FIG. 53, where prosthesis2500is shown attached to natural vertebra2005with rods2146which pass through, and snap into engagement with, prosthetic pedicles2515.

Having thus described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the embodiments shown herein are provided by way of example only, and that various changes and modifications may be effected by one skilled in the art without departing from the scope or spirit of the invention as defined in the claims.