HYBRID MULTIFUNCTIONAL POSTERIOR INTERSPINOUS FUSION DEVICE
An interspinous stabilization device is provided that more evenly distributes loads throughout the adjacent vertebrae than known interspinous stabilization devices, and further can readily compensate for graft settling so as to maintain continued axial loading of the graft material.
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This application is a divisional application of U.S. Ser. No. 14/379,139 filed Aug. 15, 2014, now U.S. Pat. No. 10,188,434 issued Jan. 29, 2019, which is a national stage application filed under 35 USC § 371 of international application PCT/US2013/026665 filed Feb. 19, 2013, which claims the priority to United States provisional application Ser. No. 61/599,988 filed Feb. 17, 2012, the disclosure of which is incorporated herein by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot applicable.
BACKGROUND OF THE INVENTIONThis invention relates in general to an improved structure for a hybrid multifunctional posterior interspinous fusion device.
An interspinous stabilization device is a device that is adapted to be secured to two or more adjacent vertebrae of a spine in order to stabilize the relative positioning therebetween. An interspinous stabilization device can also be used to facilitate the placement of a bone-growth material, such as a bone graft material, between such adjacent vertebrae to enhance bone growth and promote fusion of the adjacent vertebrae.
Wolff s law of dynamic osteosynthesis states that every change in the function of a bone is followed by definitive changes in its internal architecture and secondary alterations in its external confirmation. This means that osseous tissues remodel in direct response to the stresses placed upon them. Although known interspinous stabilization devices have functioned satisfactorily for stabilizing the relative positioning of the adjacent vertebrae to which they are connected, they are not well suited for desirably maintaining axial compression on a bone graft material that is disposed between such adjacent vertebrae after graft settling occurs, such as described in Wolff s law. Thus, it would be desirable to provide an improved structure for an interspinous stabilization device that more evenly distributes loads throughout the adjacent vertebrae than known structures, and further readily compensates for graft settling so as to maintain continued axial loading of the graft.
SUMMARY OF THE INVENTIONThis invention relates to an improved structure for an interspinous stabilization device that more evenly distributes loads throughout the adjacent vertebrae than known interspinous stabilization devices, and further readily compensates for graft settling so as to maintain continued axial loading of the graft.
More specifically, this invention relates to a medical device that helps in performing a spinal fusion procedure by holding the bone graft in place and stabilizing the facet screw by a plate that is attached to it. The invention also performs a dynamic function that compensates for settling of the bone graft over time. This dynamic function may, if desired, be enhanced by a movement-limiting mechanism that allows extension but not flexion such that the bone graft fusion remains in contact and fusion takes place. Thus, the interspinous stabilization device of this invention is a multipurpose device that both more evenly distributes loads throughout the adjacent vertebrae than known interspinous stabilization devices, and further readily compensates for graft settling so as to maintain continued axial loading of the graft. A mounting plate of the interspinous fusion device may be secured to a body portion therein in either a fixed or poly-axial manner so as to provide better stability in lateral bending and rotation.
Some of the indications for use of the interspinous fusion device of this invention may include: (1) supplemental fixation for anterior lumbar interbody fusion (ALIF) procedures; (2) supplemental fixation for transforaminal lumbar interbody fusion TLIP) procedures; (3) supplemental fixation lateral interbody fusion procedures; (4) posterior interlaminar fusion; (5) posterolateral fusion; (6) fusion in pars defect with facet pedicular screw; (7) fusion in Grade I spondolystheis; and (8) revision option in failed fusion/hybrid constructs.
Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the various embodiments of the invention, when read in light of the accompanying drawings.
Referring now to the drawings, there is illustrated in
As best shown in
First and second mounting plates 16 and 17 are respectively secured to the rear wall 14 of the interspinous fusion device 10, extending upwardly therefrom above the side walls 12 and 13, respectively. The mounting plates 16 and 17 have respective inwardly facing serrated surfaces 16a and 17a provided thereon, the purpose of which will be explained below. First and second mounting plates 18 and 19 are respectively secured to the upper ends of the first and second mounting plates 16 and 17. In the illustrated embodiment, the mounting plates 18 and 19 extend laterally outwardly in opposite directions from the upper ends of the mounting plates 16 and 17, although such is not required. Each of the illustrated mounting plates 18 and 19 is shaped having a torsional twist as it extends laterally outwardly from the associated brackets 16 and 17. However, the mounting plates 18 and 19 may have any desired shape or combination of shapes. Additionally, the mounting plates 18 and 19 need not be fixed in position relative to the associated brackets 16 and 17, but rather may be movable relative thereto in a poly-axial manner, as described below. In either event, the mounting plates 18 and 19 have respective apertures 18a and 19a formed therethrough for a purpose that will be explained below.
First and second connecting plates 20 and 21 are respectively secured to the lower ends of the first and second side walls 12 and 13 of the central body portion of the interspinous fusion device 10. In the illustrated embodiment, the connecting plates 20 and 21 are each generally planar and extend parallel to one another. However, the connecting plates 20 and 21 may have any desired shape or combination of shapes. The connecting plates 20 and 21 have respective slot-shaped apertures 20a and 21a formed therethrough. The purposes for the connecting plates 20 and 21 and the slot-shaped apertures 20a and 21a will be explained below.
The interspinous fusion device 10 is adapted to be secured to pair of adjacent vertebrae (not shown) in a spine to stabilize the relative positioning therebetween and to facilitate the placement of a bone-growth material, such as a bone graft material, to enhance bone growth and fusion of the adjacent vertebrae. To accomplish this, the first and second mounting plates 18 and 19 are adapted to be secured to an upper one of the pair of adjacent vertebrae. To accomplish this, the interspinous fusion device 10 is initially positioned such that the first and second mounting plates 18 and 19 are disposed adjacent to respective facets or other portions of the upper vertebra. Then, one or more fasteners (not shown), such as conventional bone screws, can be inserted through each of the apertures 18a and 19a into engagement with the adjacent facets or other portions of the upper vertebra. In this manner, the first and second mounting plates 18 and 19 of the interspinous fusion device 10 can be secured to the upper one of the pair of adjacent vertebrae.
As shown in the drawings, either or both of the apertures 18a and 19a formed through the first and second mounting plates 18 and 19 can be shaped to permit the fasteners to extend therethrough at multiple locations. In the illustrated embodiment, both of the apertures 18a and 19a are irregularly shaped so as to define plural discrete positions on the mounting plates 18 and 19 through which the fasteners may extend into engagement with the adjacent facets or other portions of the upper vertebra. These plural discrete positions provide desirable flexibility during the installation process, inasmuch as the geometries of each of the upper pair of adjacent vertebrae can vary in accordance with the specific anatomy of the patient. The interspinous fusion device 10 of this invention can readily accommodate such variations in anatomy because the fasteners can be provided at any selected one of the plural discrete positions defined by the apertures 18a and 19a that is deemed to be most appropriate based upon such anatomy.
Additionally, as discussed above, the illustrated mounting plates 18 and 19 extend laterally outwardly in opposite directions from the upper ends of the side walls 12 and 13, and each is shaped having a torsional twist. The shapes of the first and second mounting plates 18 and 19 are such that relatively large surface areas thereof engage the respective facets or other portions of the upper vertebra. Such relatively large surface area engagement functions to distribute load forces imparted by the interspinous fusion device 10 more evenly across the surface areas of the respective facets or other portions of the upper vertebra. As a result, the generation of undesirable localized stresses on the facets or other portions of the upper vertebra is substantially reduced or avoided.
The first and second connecting plates 20 and 21 of the interspinous fusion device are adapted to be secured to a lower one of the pair of adjacent vertebrae. To accomplish this, the interspinous fusion device 10 is initially positioned such that the first and second connecting plates 20 and 21 are disposed about a spinous process or other portion of the lower vertebra. Then, one or more fasteners (not shown), such as conventional bone screws, can be inserted through each of the slot-shaped apertures 20a and 21a of the connecting plates 20 and 21 and through the spinous process or other portion of the lower vertebra. In this manner, the first and second connecting plates 20 and 21 of the interspinous fusion device 10 can be secured to the lower one of the pair of adjacent vertebrae.
As mentioned above, the bottom wall 11, the side walls 12 and 13, and the rear wall 14 cooperate to define a partially enclosed space within the interspinous fusion device 10. This partially enclosed space can be used to receive a quantity of a bone-growth material, such as a bone graft material, to enhance bone growth and fusion of the adjacent vertebrae. The partially enclosed space within the interspinous fusion device further functions to prevent the bone-growth material from undesirably flowing out of the region between the adjacent vertebrae. The inwardly facing serrated surfaces 12a and 13a and the apertures 12b and 13b on the side walls 12 and 13 provide irregularly shaped surfaces that are well adapted to be engaged by the bone-growth material, thereby functioning to positively retain such material within the central body portion of the interspinous fusion device 10. The mounting inwardly facing serrated surfaces 16a and 17a of the mounting plates 16 and 17 function in the same manner.
As also mentioned above, the interspinous stabilization device 10 of this invention not only more evenly distributes loads throughout the adjacent vertebrae than known interspinous stabilization devices, but also can readily compensate for graft settling so as to maintain continued axial loading of the graft material disposed between the adjacent vertebrae. In the interspinous stabilization device 10 of this invention, this is accomplished by the provision of the two slot-shaped apertures 20a and 21a formed through the connecting plates 20 and 21. During the above-described installation process, the first and second connecting plates 20 and 21 are disposed about a spinous process or other portion of the lower vertebra, and a fastener is inserted through the slot-shaped apertures 20a and 21a and through the spinous process of the lower vertebra. As settling of the bone graft material occurs, the fastener can slide through the slot-shaped apertures 20a and 21a, thereby allowing the distance between the two adjacent vertebrae to decrease as settling of the bone graft occurs. Consequently, the axial pressure exerted by such adjacent vertebrae on the bone graft material is effectively maintained as settling of the bone graft material occurs.
Additionally, as also described above, the slot 14 a formed between portions of the side walls 12 and 13 and the rear wall 14 defines a spring-like hinge between the bottom wall 11 and the rear wall 14 of the interspinous fusion device 10. This spring-like hinge allows a limited amount of pivoting movement of the rear wall 14 relative to the bottom wall 11. As a result, the axial pressure exerted by such adjacent vertebrae on the bone graft material is effectively maintained as settling of the bone graft material occurs.
Thus, the dynamic system of this invention is designed to take full advantage of Wolff s law of dynamic osteosynthesis. By avoiding stress shielding and allowing full load sharing, earlier and more substantial graft incorporation can occur. The unique slot-shaped apertures 20a and 21a and slot 14a are designed to compensate for graft setting (bone graft or special scaffold material, such as calcium phosphate, etc.) so as to maintain continued axial loading on the graft. Axial settling, which allows full load sharing capability, occurs because the fasteners are free to move through the slot-shaped apertures 20a and 21 formed through the first and second connecting plates 20 and 21 and because the spring-like hinge defined between the bottom wall 11 and the rear wall 14 of the interspinous fusion device 10 allows a limited amount of pivoting movement of the mounting plates 16 and 17 (which are connected to the upper vertebra) relative to the connecting plates 20 and 21 (which are connected to the lower vertebra). As a result, the amount of this settling distance is determined by the amount of graft resorption, not because of any physical restriction imposed by the interspinous stabilization device 10 of this invention. Also, compression of the bone graft material as explained above is facilitated.
Referring now to
Referring now to
In the illustrated embodiment, this is accomplished by providing each of mounting plates 116 and 117 with a mounting structure 116b and 117b, and further by providing each of the mounting plates 118 and 119 with a cooperating mounting structure 118a and 119a. As shown in
As shown in
In
In
Referring now to
Referring now to
Referring now to
As best shown in
First and second mounting plates 416 and 417 are respectively secured to the upper side walls 414 and 415. The mounting plates 416 and 417 have respective apertures 416a and 417a or other structures provided thereon to facilitate the securement of the interspinous fusion device 410 to an upper one of the pair of adjacent vertebrae, as described above. In the illustrated embodiment, the mounting plates 416 and 417 are each generally planar and extend parallel to one another. However, the mounting plates 416 and 417 may have any desired shape or combination of shapes. Similarly, first and second connecting plates 420 and 421 are respectively secured to the lower side walls 414 and 415. The connecting plates 420 and 421 have respective apertures 420a and 421a or other structures provided thereon to facilitate the securement of the interspinous fusion device 410 to a lower one of the pair of adjacent vertebrae, as also described above. In the illustrated embodiment, the connecting plates 420 and 421 are each generally planar and extend parallel to one another. However, the connecting plates 420 and 421 may have any desired shape or combination of shapes.
The relationship between the size and shape of the gap 415c in the interspinous fusion device 410 and the size and shape of the bone graft material 450 is advantageous. In particular, it is desirable that this relationship be such that a relatively high compression be placed upon the bone graft material 450 while imposing a relatively low stress on the interspinous fusion device 410. The relatively high compression placed upon the bone graft material 450 facilitates that the bone graft material 450 remain in a desired position relative to the interspinous fusion device 410 and, thus, to the vertebrae to which the interspinous fusion device 410 is to be secured. The relatively low stress imposed upon the interspinous fusion device 410 minimizes the likelihood that damage may occur during or after installation of the bone graft material 450. The interspinous fusion device 410 may be formed from any desired material including, but not limited to, polyether ether ketone (PEEK), titanium, nitinol (nickel titanium), cortical bone, and composites.
Referring now to
In use, the sixth embodiment of the interspinous fusion device 510 is installed by initially releasing the locking nut 513d so that the lower side walls 511 and 512 are free to pivot relative to the upper side walls 514 and 515. Then the interspinous fusion device 510 is installed by securing the mounting plates 416 and 417 to an upper one of the pair of adjacent vertebrae, and further by securing the connecting plates 420 and 421 to a lower one of the pair of adjacent vertebrae, as also described above. Thereafter, the locking nut 513d is tightened on the pivot pin 513c so as to maintain the lower side walls 511 and 512 in a predetermined position relative to the upper side walls 514 and 515. This structure allows the spacing between the first and second opposed lower side walls 511 and 512 and the first and second opposed upper side walls 514 and 515 to be customized to the specific anatomy of the patient.
Referring now to
The interspinous fusion device 610 is assembled by initially aligning the protrusion 613b provided on the first portion 610a with the recess 613a provided on the second portion 610b as shown in
The principle and mode of operation of this invention have been explained and illustrated in its various embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.
Claims
1. An interspinous stabilization device comprising:
- a body portion;
- a pair of mounting plates supported on the body portion and adapted to engage a first vertebra; and
- a pair of connecting plates supported on the body portion and adapted to engage a second vertebra,
- wherein the interspinous stabilization device is adapted to maintain continued axial loading of a graft disposed between the first and second vertebra as settling of the graft occurs.
2. The interspinous stabilization device defined in claim 1, wherein one or both of the mounting plates are shaped having a torsional twist.
3. The interspinous stabilization device defined in claim 1, wherein one or both of the mounting plates has an aperture formed therethrough that is shaped to permit a fastener to extend therethrough at multiple locations.
4. The interspinous stabilization device defined in claim 1, wherein one or both of the connecting plates has a slot-shaped aperture formed therethrough.
5. The interspinous stabilization device defined in claim 1, wherein the body portion is defined by a bottom wall, first and second opposed side walls, and a rear wall that cooperate to define a partially enclosed space for the receipt of a bone graft material.
6. The interspinous stabilization device defined in claim 1, wherein one or both of the mounting plates is fixed in position relative to the body portion.
7. The interspinous stabilization device defined in claim 1, wherein one or both of the mounting plates is movable relative to the body portion and lockable in a desired position relative thereto.
8. The interspinous stabilization device defined in claim 1, wherein the body portion is defined by a bottom wall, first and second opposed side walls, and a rear wall, and wherein a hinge is provided between the bottom wall and the rear wall to allow relative pivoting movement therebetween.
9. The interspinous stabilization device defined in claim 8, further including a movement-limiting mechanism to restrict the pivoting movement of the rear wall relative to the bottom wall to a single rotational direction.
10. The interspinous stabilization device defined in claim 1, wherein one or both of the mounting plates has a generally uniform thickness.
11. The interspinous stabilization device defined in claim 1, wherein one or both of the mounting plates varies in thickness from end to end.
12. The interspinous stabilization device defined in claim 1, wherein one or both of the mounting plates is linear from end to end.
13. The interspinous stabilization device defined in claim 1, wherein one or both of the mounting plates is curved from end to end.
14. The interspinous stabilization device defined in claim 1, wherein one or both of the mounting plates has a slot-shaped aperture formed therethrough.
15. The interspinous stabilization device defined in claim 5, wherein one or both of the side walls are pivotably connected to the rear wall.
16. The interspinous stabilization device defined in claim 5 wherein one or both of the mounting plates are pivotably connected to the rear wall.
17. The interspinous stabilization device defined in claim 1, wherein either or both of the pair of mounting plates is pivotably supported on the body portion.
18. The interspinous stabilization device defined in claim 1, wherein either or both of the pair of connecting plates is pivotably supported on the body portion.
19. The interspinous stabilization device defined in claim 1, wherein the body portion includes a spring-like hinge between the pair of mounting plates and the pair of connecting plates.
20. The interspinous stabilization device defined in claim 19, wherein the spring-like hinge is defined by a slot that extends between the pair of mounting plates and the pair of connecting plates.
21. The interspinous stabilization device defined in claim 19, wherein the slot has a length of about 12 mm.
22. The interspinous stabilization device defined in claim 19, wherein the slot expands at an angular relationship of about 2°.
23. The interspinous stabilization device defined in claim 1, wherein the body portion includes a hinge between the pair of mounting plates and the pair of connecting plates.
24. The interspinous stabilization device defined in claim 23, wherein the hinge includes a pivot pin that extends through portions of the pair of mounting plates and the pair of connecting plates.
25. The interspinous stabilization device defined in claim 24, further including a mechanism for maintaining the pair of mounting plates in a predetermined position relative to the pair of connecting plates.
26. The interspinous stabilization device defined in claim 25, wherein the mechanism for maintaining includes a locking nut provided on the pivot pin.
27. The interspinous stabilization device defined in claim 1, wherein the interspinous fusion device is split into two separate lateral portions that are supported on one another.
28. The interspinous stabilization device defined in claim 27, wherein a first lateral portion has a protrusion provided thereon, and wherein a second lateral portion has a recess provided therein that receives the protrusion.
29. The interspinous stabilization device defined in claim 28, wherein the recess and the protrusion are sized and shaped in a complementary manner.
30. The interspinous stabilization device defined in claim 28, wherein the recess and the protrusion are U-shaped.
31. An interspinous stabilization device that is connected to a plate so as to directly stabilize a spinous process with a facet joint in a vertebra in a spine.
Type: Application
Filed: Jan 28, 2019
Publication Date: May 23, 2019
Applicant: The University of Toledo (Toledo, OH)
Inventors: Anand K. Agarwal (Toledo, OH), Vijay K. Goel (Toledo, OH), Aakash Agarwal (Toledo, OH)
Application Number: 16/258,967