US20100087864A1 - Fastener assembly that fastens to polyaxial pedicle screw - Google Patents

Abstract

A fastener assembly including an existing polyaxial pedicle screw that has been previously installed in a spinal structure, the polyaxial pedicle screw including a polyaxial head to which a prosthetic member is secured, a fastening portion fastened to the polyaxial head over the prosthetic member, and a connector element that extends from the fastening portion, the connector element being connected to another spinal structure.

Description

FIELD OF THE INVENTION
• This invention relates generally to polyaxial fasteners, such as a polyaxial pedicle screw assembly, and particularly to a fastener assembly that fastens to polyaxial pedicle screws that have already been installed in spinal structure.
BACKGROUND OF THE INVENTION
• Polyaxial pedicle screw assemblies are well known in the art and may be used for connecting vertebrae or other spinal structure to rods in spinal surgery. For example, polyaxial pedicle screw assemblies are known that incorporate a ball joint at the connection to the rod to allow the surgeon some flexibility in placing the screws. Tightening a nut on the screw compresses the ball joint components to lock the angular position of the ball joint.
SUMMARY OF THE INVENTION
• The present invention seeks to provide a fastener assembly that fastens to polyaxial pedicle screws that have already been installed in spinal structure, as is described more in detail hereinbelow. The fastener assembly of the present invention may be used to fasten different elements to the pedicle screws, such as but not limited to, fusion rods between adjoining vertebrae or crossbars and other connections from the pedicle screws to any suitable portion of the spine in the patient.
• The present invention provides the possibility of connecting with cross connectors to fusion systems directly to the pedicle screw and not between the fusion rods as in current prior art systems.
• There is thus provided in accordance with an embodiment of the invention a fastener assembly including an existing polyaxial pedicle screw that has been previously installed in a spinal structure, the polyaxial pedicle screw including a polyaxial head to which a prosthetic member is secured, a fastening portion fastened to the polyaxial head over the prosthetic member, and a connector element that extends from the fastening portion, the connector element being connected to another spinal structure.
• In accordance with an embodiment of the invention the fastening portion includes a wedge ring and the connector element includes a conical ring into which the wedge ring fits, the connector element including a connecting member that extends from the conical ring, wherein the wedge ring is sized to fit over the polyaxial head and the conical ring wedges the wedge ring onto the polyaxial head.
• Further in accordance with an embodiment of the invention the wedge ring has a conical periphery with a top surface that has a larger outer diameter than a bottom surface thereof, and the conical ring has a top surface with a larger inner diameter than a bottom surface thereof, the larger outer diameter not being greater than the larger inner diameter. A plurality of grooves may be formed in the conical periphery of the wedge ring. One or more of the grooves may be open at the top surface and closed at the bottom surface and one or more other grooves may be closed at the top surface and open at the bottom surface.
• In accordance with another embodiment of the invention the fastening portion includes a closed ring and the connector element includes a connecting member that extends from the closed ring, and wherein the existing polyaxial pedicle screw includes a first mechanical fastener fastened to the polyaxial head, wherein the closed ring is placed over the first mechanical fastener such that the first mechanical fastener protrudes through the closed ring, and further including a second mechanical fastener that fastens to the first mechanical fastener and is tightened against the closed ring.
• In accordance with yet another embodiment of the invention the fastening portion includes an open ring that fits over the polyaxial head and a mechanical fastener that fastens end portions of the open ring towards each other so as to clamp the open ring onto the polyaxial head, and the connector element includes a connecting member that extends from the open ring. The end portions of the open ring can be angled at an acute angle with respect to a top surface of the open ring.
• There is also provided in accordance with an embodiment of the invention a method including fastening a fastening assembly to a polyaxial head of an existing polyaxial pedicle screw that has been previously installed in a spinal structure, a prosthetic member being secured to the polyaxial head, wherein the fastening assembly includes a fastening portion fastened to the polyaxial head over the prosthetic member and a connector element that extends from the fastening portion, and connecting the connector element to another spinal structure.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:
• FIG. 1 is a simplified pictorial illustration of a fastener assembly, constructed and operative in accordance with an embodiment of the present invention, showing two such fastener assemblies with wedge rings and connector elements secured to polyaxial pedicle screw heads that have previously been installed in the left and right sides of vertebra;
• FIGS. 2A and 2B are partially sectional illustrations of the wedge ring and connector element ofFIG. 1;
• FIG. 3A is an exploded illustration of the wedge ring, the connector element and a fastening tool used to secure the fastener assembly on an existing polyaxial pedicle screw, in accordance with an embodiment of the present invention;
• FIG. 3B is a pictorial illustration of the wedge ring and connector element mounted in the fastening tool;
• FIGS. 3C and 3D are pictorial illustrations of the fastening tool with the wedge ring and connector element placed over the existing polyaxial pedicle screw;
• FIGS. 3E and 3F are pictorial illustrations of using the fastening tool to secure the fastening assembly ofFIG. 1 on to the existing polyaxial pedicle screw;
• FIG. 4 is a simplified pictorial illustration of a fastener assembly, constructed and operative in accordance with another embodiment of the present invention, showing two such fastener assemblies with closed rings and connector elements secured to polyaxial pedicle screw heads that have previously been installed in the left and right sides of vertebra;
• FIG. 5 is a partially sectional illustration of the closed ring and connector element ofFIG. 4;
• FIG. 6A is a pictorial illustration of fastening a set screw of the fastener assembly ofFIG. 4 on an existing polyaxial pedicle screw, in accordance with an embodiment of the present invention;
• FIG. 6B is a pictorial illustration of placing the connector element of the fastener assembly ofFIG. 4 on the set screw;
• FIGS. 6C and 6D are pictorial illustrations of a nut of the fastener assembly ofFIG. 4 mounted in a fastening tool used to secure the fastener assembly on an existing polyaxial pedicle screw, in accordance with an embodiment of the present invention;
• FIG. 6E is a pictorial illustration of feeding a torque handle through a counter torque handle of the fastening tool;
• FIG. 6F is a pictorial illustration of using the fastening tool to secure the fastening assembly ofFIG. 4 on to the existing polyaxial pedicle screw;
• FIG. 7 is a simplified pictorial illustration of a fastener assembly, constructed and operative in accordance with yet another embodiment of the present invention, showing two such fastener assemblies with open rings and connector elements secured to polyaxial pedicle screw heads that have previously been installed in the left and right sides of vertebra;
• FIG. 8 is a more detailed illustration of the open ring and connector element ofFIG. 7;
• FIG. 9A is a pictorial illustration of fastening a set screw of the existing polyaxial pedicle screw while the fastener assembly ofFIG. 7 is mounted on the existing polyaxial pedicle screw, in accordance with an embodiment of the present invention;
• FIG. 9B is a pictorial illustration of a tool used to fasten the set screw of the existing polyaxial pedicle screw;
• FIG. 9C is a pictorial illustration of aligning the fastener assembly ofFIG. 7 on the existing polyaxial pedicle screw, in accordance with an embodiment of the present invention;
• FIG. 9D is a pictorial illustration of a tool used to align the fastener assembly ofFIG. 7 on the existing polyaxial pedicle screw; and
• FIG. 9E is a pictorial illustration of tightening a set screw of the fastener assembly ofFIG. 7 on the existing polyaxial pedicle screw.
DETAILED DESCRIPTION OF EMBODIMENTS
• Reference is now made toFIG. 1, which illustrates afastener assembly10, constructed and operative in accordance with a non-limiting embodiment of the present invention.
• Fastener assembly10 includes one or more existing polyaxial pedicle screws12 (in the illustrated embodiment left and right screws are shown) that have been previously installed in a spinal structure (e.g., pedicles, articular processes, etc.). Thepolyaxial pedicle screw12 includes apolyaxial head14 to which aprosthetic member16 is secured. In the non-limiting illustrated embodiment,prosthetic member16 are the prongs of a TOPS (total posterior spine implant) brand spinal prosthesis, commercially available from the present assignee and described in US Patent7011685, the disclosure of which is incorporated herein by reference.
• Reference is now made toFIGS. 2A and 2B. Aset screw22 is screwed in the female threads ofpolyaxial head14 and clamps down onprosthetic member16. A fastening portion18 (described more in detail below) is fastened to thepolyaxial head14 over theprosthetic member16. Aconnector element20 extends from fasteningportion18. As seen inFIG. 1,connector element20 is connected to another spinal structure (e.g., adjacent lumbar vertebra).
• In accordance with an embodiment of the invention,fastening portion18 includes awedge ring24 andconnector element20 includes aconical ring26 into whichwedge ring24 fits.Connector element20 includes a connectingmember28 that extends fromconical ring26, such as a rod, bar, plate and the like.Wedge ring24 is sized to fit overpolyaxial head14 andconical ring26wedges wedge ring24 ontopolyaxial head14.
• As seen inFIG. 2B,wedge ring24 has a conical periphery with a top surface that has a larger outer diameter than a bottom surface thereof, andconical ring26 has a top surface with a larger inner diameter than a bottom surface thereof, the larger outer diameter ofwedge ring24 not being greater than the larger inner diameter ofconical ring26. As seen inFIG. 3A, a plurality of grooves30 may be formed in the conical periphery ofwedge ring24. One or more of the grooves30 may be open at the top surface and closed at the bottom surface and one or more other grooves30 may be closed at the top surface and open at the bottom surface.
• The fastener assemblies of the present invention may be constructed of any suitable, rigid, medically safe material, such as but not limited to, stainless steel alloy (e.g., AISI 316L), titanium or titanium alloy or chrome cobalt alloy, PEEK, shape memory alloys or polymers, and any combination thereof.
• Reference is now made toFIGS. 3A-3F, which illustrate installingwedge ring24 andconnector element20 on thepedicle screw12.
• Afastening tool32 is used to secure the fastener assembly on the existing polyaxial pedicle screw.FIGS. 3A and 3B showwedge ring24 andconnector element20 inserted in jaws offastening tool32.FIGS. 3C and 3Dshow fastening tool32 withwedge ring24 andconnector element20 placed over the existing polyaxial pedicle screw14. Thefastening tool32 has analignment indicator34 that indicates the proper alignment ofconnector element20 with the existingprosthetic member16.
• FIGS. 3E and 3F show using thefastening tool32 to securefastening assembly10 on to the existing polyaxial pedicle screw10.Handles36 offastening tool32 may be squeezed so thatconical ring26wedges wedge ring24 ontopolyaxial head14 as described above with reference toFIGS. 2A-2B.
• The set screw of the existing pedicle screw may be left loose or loosened somewhat during installation of the fastener assembly on the existing polyaxial pedicle screw and afterwards tightened to the recommended torque.
• Reference is now made toFIGS. 4 and 5. In accordance with another embodiment of the invention the fastening portion of the fastening assembly includes aclosed ring40 and the connector element includes a connectingmember42 that extends from closedring40. The existing polyaxial pedicle screw12 includes a first mechanical fastener44 (such as but not limited to, an elongate set screw with a central through hole) fastened topolyaxial head14.Closed ring40 is placed over the firstmechanical fastener44 such that the firstmechanical fastener44 protrudes through closedring40. A second mechanical fastener46 (such as but not limited to, a nut) fastens to the firstmechanical fastener44 and is tightened against closedring40, thereby securing the fastening portion of the fastening assembly to the existing polyaxial pedicle screw12.
• Reference is now made toFIGS. 6A-6F. InFIG. 6A, atool45 is used to screw the firstmechanical fastener44 on thepolyaxial head14 against theprosthetic member16. InFIG. 6B, theclosed ring40 of the connector element is placed over first mechanical fastener44 (firstmechanical fastener44 goes through the hole of the closed ring40). The firstmechanical fastener44 may be further tightened a little at this time.
• FIGS. 6C and 6D illustrate secondmechanical fastener46 mounted in a fastening tool (torque handle tool)47 used to secure the fastener assembly on the existing polyaxial pedicle screw.FIG. 6E illustrates feeding thetorque handle tool47 through acounter torque handle48. As seen inFIG. 6F, the counter torque handle48 is used to hold the fastening assembly in proper alignment on the existing polyaxial pedicle screw12.Torque handle tool47 is used to tighten secondmechanical fastener46 against closedring40, thereby securing the fastening portion of the fastening assembly to the existing polyaxial pedicle screw12.
• Reference is now made toFIGS. 7 and 8. In accordance with yet another embodiment of the invention the fastening portion includes anopen ring50 that fits over thepolyaxial head14 and amechanical fastener52 that fastensend portions54 of theopen ring50 towards each other so as to clamp theopen ring50 onto thepolyaxial head14. The connector element includes a connectingmember56 that extends fromopen ring50. Theend portions54 of theopen ring50 can be angled at an acute angle with respect to a top surface of theopen ring50.
• Reference is now made toFIGS. 9A-9E. InFIG. 9A, a fastening tool58 (also shown inFIG. 9B) is used to fasten the set screw of the existing polyaxial pedicle screw while the fastener assembly ofFIG. 7 is mounted on the existing polyaxial pedicle screw.
• InFIG. 9C, a dedicated alignment tool60 (also shown inFIG. 9D) is used to align the fastener assembly ofFIG. 7 on the existing polyaxial pedicle screw12.
• InFIG. 9E, a tighteningtool62 is used to tighten the mechanical fastener of the fastener assembly ofFIG. 7 so as to clamp theopen ring50 onto thepolyaxial head14.
• It is appreciated that various features of the invention which are, for clarity, described in the contexts of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Claims (10)

1. A fastener assembly comprising:

an existing polyaxial pedicle screw that has been previously installed in a spinal structure, said polyaxial pedicle screw comprising a polyaxial head to which a prosthetic member is secured;

a fastening portion fastened to said polyaxial head over said prosthetic member; and

a connector element that extends from said fastening portion, said connector element being connected to another spinal structure.

2. The fastener assembly according toclaim 1, wherein said fastening portion comprises a wedge ring and said connector element comprises a conical ring into which said wedge ring fits, said connector element comprising a connecting member that extends from said conical ring, wherein said wedge ring is sized to fit over said polyaxial head and said conical ring wedges said wedge ring onto said polyaxial head.

3. The fastener assembly according toclaim 2, wherein said wedge ring has a conical periphery with a top surface that has a larger outer diameter than a bottom surface thereof, and said conical ring has a top surface with a larger inner diameter than a bottom surface thereof, said larger outer diameter not being greater than said larger inner diameter.

4. The fastener assembly according toclaim 3, wherein a plurality of grooves are formed in said conical periphery of said wedge ring.

5. The fastener assembly according toclaim 4, wherein at least one of said grooves is open at the top surface and closed at the bottom surface and at least another groove is closed at the top surface and open at the bottom surface.

6. The fastener assembly according toclaim 1, wherein said fastening portion comprises a closed ring and said connector element comprises a connecting member that extends from said closed ring, and wherein said existing polyaxial pedicle screw comprises a first mechanical fastener fastened to the polyaxial head, wherein said closed ring is placed over said first mechanical fastener such that said first mechanical fastener protrudes through said closed ring, and further comprising a second mechanical fastener that fastens to said first mechanical fastener and is tightened against said closed ring.

7. The fastener assembly according toclaim 6, wherein said closed ring is not flush with said connecting member.

8. The fastener assembly according toclaim 1, wherein said fastening portion comprises an open ring that fits over said polyaxial head and a mechanical fastener that fastens end portions of said open ring towards each other so as to clamp said open ring onto said polyaxial head, and said connector element comprises a connecting member that extends from said open ring.

9. The fastener assembly according toclaim 8, wherein said end portions of said open ring are angled at an acute angle with respect to a top surface of said open ring.

10. A method comprising:

fastening a fastening assembly to a polyaxial head of an existing polyaxial pedicle screw that has been previously installed in a spinal structure, a prosthetic member being secured to said polyaxial head, wherein said fastening assembly comprises a fastening portion fastened to said polyaxial head over said prosthetic member and a connector element that extends from said fastening portion; and

connecting said connector element to another spinal structure.

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