Intervertebral prosthetic device for spinal stabilization and method of implanting same

The present invention relates to an intervertebral prosthetic device for stabilizing the human spine, and a method of implanting same.

Spinal discs that extend between adjacent vertebrae in vertebral columns of the human body provide critical support between the adjacent vertebrae. These discs can rupture, degenerate, and/or protrude by injury, degradation, disease, or the like, to such a degree that the intervertebral space between adjacent vertebrae collapses as the disc loses at least a part of its support function, which can cause impingement of the nerve roots and severe pain.

In these cases, intervertebral prosthetic devices have been designed that can be implanted between the adjacent vertebrae, both anterior and posterior of the column, to prevent the collapse of the intervertebral space between the adjacent vertebrae and thus stabilize the spine.

However, many of these devices have less than optimum biomechanics, are relatively difficult to insert, have insufficient strength, and often do not provide an optimum fit with the anatomy.

Therefore, the intervertebral prosthetic device according to an embodiment of the invention overcomes the above deficiencies by providing improved biomechanics and increased strength, in addition to being relatively easy to insert, yet provides an improved fit with the anatomy.

Various embodiments of the invention may possess one or more of the above features and advantages, or provide one or more solutions to the above problems existing in the prior art.

FIG. 1 is a side elevational view of an adult human vertebral column.

FIG. 2 is a posterior elevational view of the column of FIG. 1 .

FIG. 3 is an enlarged, front elevational view of one of the vertebrae of the column of FIGS. 1 and 2 .

FIG. 4 is an enlarged, partial, isometric view of a portion of the column of FIGS. 1 and 2 , including the lower three vertebrae of the column, and depicting an intervertebral prosthetic device according to an embodiment of the invention inserted between two adjacent vertebrae.

FIG. 5 is an enlarged, isometric, view of the prosthetic device of FIG. 3 .

FIG. 6 is an enlarged, top plan view of the prosthetic device of FIG. 5 .

FIGS. 7 is a cross-sectional view taken along the line 7 - 7 of FIG. 6 .

With reference to FIGS. 1 and 2 , the reference numeral 10 refers, in general, to a human vertebral column 10 . The lower portion of the vertebral column 10 is shown and includes the lumbar region 12 , the vertebrae V 6 , and the coccyx 16 . The flexible, soft portion of the vertebral column 10 , which includes the thoracic region and the cervical region, is not shown.

The lumbar region 12 of the vertebral column 10 includes five vertebrae V 1 , V 2 , V 3 , V 4 and V 5 separated by intervertebral discs D 1 , D 2 , D 3 , and D 4 , with the disc D 1 extending between the vertebrae V 1 and V 2 , the disc D 2 extending between the vertebrae V 2 and V 3 , the disc D 3 extending between the vertebrae V 3 and V 4 , and the disc D 4 extending between the vertebrae V 4 and VS.

The vertebrae V 6 includes five fused vertebrae, one of which is a superior vertebrae V 6 separated from the vertebrae VS by a disc D 5 . The other four fused vertebrae of the sacrum 14 are referred to collectively as V 7 . A disc D 6 separates the vertebrae V 6 from the coccyx 16 which includes four fused vertebrae (not referenced).

With reference to FIG. 3 , the vertebrae V 5 includes two laminae 20 a and 20 b extending to either side (as viewed in FIG. 2 ) of a spinous process 22 that extends posteriorly from the juncture of the two laminae. Two transverse processes 24 a and 24 b extend laterally from the laminae 20 a and 20 b , respectively. Two articular processes 26 a and 26 b extend superiorly from the laminae 20 a and 20 b , respectively, and two articular processes 28 a and 28 b extend inferiorly from the laminae 20 a and 20 b , respectively. The inferior articular processes 28 a and 28 b rest in the superior articular process of the vertebra V 2 to form a facet joint. Since the other vertebrae V 1 -V 4 are similar to the vertebrae V 5 , they will not be described in detail.

Referring again to FIG. 2 , the vertebrae V 6 of the sacrum 14 includes two laminae 30 a and 30 b extending to either side (as viewed in FIG. 2 ) of a median sacral crest, or spinous process, 32 a that extends inferiorly from a ridge 34 and posteriorly from the juncture of the two laminae. The vertebrae V 6 also includes a pair of sacral wings 36 a and 36 b that extend laterally from the laminae 30 a and 30 b , respectively. Four additional axially-spaced sacral crests, or spinous processes, 32 b - 32 d are associated with the fused vertebrae V 7 of the sacrum 14 and extend inferiorly from the spinous process 32 a.

Referring to FIG. 4 , it will be assumed that, for one or more of the reasons set forth above, the vertebrae V 5 and V 6 are not being adequately supported by the disc D 4 and that it is therefore necessary to provide supplemental support and stabilization of these vertebrae. To this end, an intervertebral disc prosthetic device 40 according to an embodiment of the invention is implanted between the spinous processes 22 of the vertebrae V 5 and the crest, or spinous process 32 a , of the vertebrae V 6 .

The device is shown in detail in FIGS. 5-7 and includes a solid body member 42 having a generally rectangular cross section in each plane with the exception of several notches and cuts to be described.

In particular, two curved grooves, or notches, 42 a and 42 b are formed in the upper portions of the respective end portions of the body member, as viewed in the drawings. A laterally extending angled cut, or groove 42 c , having a curved cross section, is formed in the underside of the body member 42 below the notch 42 a , as viewed in FIG. 5 and 7 . Similarly, a laterally extending cut, or groove 42 d , also having a curved cross section, is formed in the underside of the body member 42 below the notch 42 b . The shape of the cut 42 d is such that a tab, or hook, 42 e ( FIG. 7 ) is defined on the underside of the body member.

Two laterally extending, through openings 42 f are formed through the body member 42 for receiving cables, or the like, to tether the device to the vertebrae V 5 and V 6 when the device 40 is implanted between the vertebrae VS and V 6 in the position shown in FIG. 4 .

Referring to FIG. 4 , the device 40 is inserted between the vertebrae V 5 and the vertebrae V 6 with the spinous process 22 of the vertebrae V 5 extending in the notch 42 a of the body member 42 , and the crest, or spinous process, 32 a of the vertebrae V 6 extending in the notch 42 b of the body member. The groove 42 c ( FIGS. 5 and 7 ) thus extends superiorly and extends around the corresponding edges of the laminae 30 a and 30 b ( FIG. 2 ) of the vertebrae V 5 , and the groove 42 d extends inferiorly and fits around the ridge 34 ( FIG. 2 ) of the vertebrae V 6 , with the tab 42 e extending under the latter ridge.

It is understood that the body member 42 can be fabricated from any conventional material or combination of materials. For example, it could have an inner core of a relatively hard material, such as hard rubber or plastic, which is surrounded by a relatively soft material such as silicone, which can be molded around the core.

The device 40 is relatively easy to insert between the vertebrae V 5 and V 6 in the manner described above, and readily fits the vertebrae. The grooves 42 c and 42 d, as well as the tab 42 e, aid in retaining the device 40 in the implanted position, and the core 42 f adds strength to the device 40 , while the soft material surrounding the core minimizes damage to the processes 22 and 30 a of the vertebrae V 5 and V 6 , respectively.

Variations

It is understood that variations may be made in the foregoing without departing from the invention and examples of some variations are as follows:

Any conventional substance that promotes bone growth, such as HA coating, BMP, or the like, can be incorporated in the body member 42 ; The body member 42 may have through holes formed therein to improve integration of the bone growth; The body member 42 may vary in shape, size, composition, and physical properties; The number and location of the notches and grooves formed in the body member 42 can vary; The prosthetic device 40 can be placed between two vertebrae in the vertebral column 10 other than the ones described above; The body member 42 can be fabricated from materials other than those described above; Bilateral extrusions, or the like, can be provided on the body member 42 to enable a tethering device to be attached to the component; The prosthetic device 40 can be implanted between body portions other than vertebrae; The prosthetic device 40 can be inserted between two vertebrae following a discectemy in which a disc between the adjacent vertebrae is removed, or corpectomy in which at least one vertebrae is removed; The spatial references made above, such as “under”, “over”, “between”, “flexible, soft”, “lower”, “top”, “bottom”, etc. are for the purpose of illustration only and do not limit the specific orientation or location of the structure described above.

The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, therefore, that other expedients known to those skilled in the art, or disclosed herein, may be employed without departing from the invention or the scope of the appended claims, as detailed above. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts a nail and a screw are equivalent structures.