Box cage for intervertebral body fusion

• US 6,090,143 A
• Filed: 09/21/1998
• Issued: 07/18/2000
• Est. Priority Date: 09/21/1998
• Status: Expired due to Fees

• Current Assignee: Michael W. Meriwether, Richard L. Shockey
• Original Assignee: Michael W. Meriwether, Richard L. Shockey
• Inventors: Shockey, Richard L., Meriwether, Michael W.
• Primary Examiner(s): Isabella, David J.
• Application Number:
  US09/157,928
• Time in Patent Office: 666 Days
• Field of Search: 623/17, 606/61
• US Class Current: 623/17.11
• CPC Class Codes: A61B 17/8605 Heads, i.e. proximal ends projecting from bone
• CPC Class Codes: A61B 17/8645 Headless screws, e.g. ligament interference screws
• CPC Class Codes: A61B 17/8875 Screwdrivers, spanners or wrenches
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/446 having a circular or elliptical cross-section substantially parallel to the axis of the spine, e.g. cylinders or frustocones
• CPC Class Codes: A61F 2/447 substantially parallelepipedal, e.g. having a rectangular or trapezoidal cross-section
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2835 Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30156 triangular
• CPC Class Codes: A61F 2002/30158 trapezoidal
• CPC Class Codes: A61F 2002/30179 X-shaped
• CPC Class Codes: A61F 2002/30261 parallelepipedal
• CPC Class Codes: A61F 2002/30266 wedge-shaped parallelepipeds
• CPC Class Codes: A61F 2002/3028 polyhedral different from parallelepipedal and pyramidal
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30579 with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30593 hollow
• CPC Class Codes: A61F 2002/30777 Oblong apertures
• CPC Class Codes: A61F 2002/30785 parallel
• CPC Class Codes: A61F 2002/30789 : perpendicular with respect to each other
• CPC Class Codes: A61F 2002/30845 : with cutting edges
• CPC Class Codes: A61F 2002/3085 : with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• CPC Class Codes: A61F 2002/30868 : Square, rectangular or rhomboidal threads
• CPC Class Codes: A61F 2002/30873 : Threadings machined on non-cylindrical external surfaces
• CPC Class Codes: A61F 2002/30879 : Ribs
• CPC Class Codes: A61F 2002/30892 : parallel
• CPC Class Codes: A61F 2002/30975 : made of two halves
• CPC Class Codes: A61F 2002/30978 : using electrical discharge machining [EDM]
• CPC Class Codes: A61F 2002/4681 : by applying mechanical shocks, e.g. by hammering
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0023 : triangular
• CPC Class Codes: A61F 2230/0026 : trapezoidal
• CPC Class Codes: A61F 2230/0058 : X-shaped
• CPC Class Codes: A61F 2230/0063 : Three-dimensional shapes
• CPC Class Codes: A61F 2230/0082 : parallelepipedal
• CPC Class Codes: A61F 2310/00017 : Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00161 : Carbon; Graphite

Abstract

An interbody implant for enhancing fusion of adjacent vertebral bodies comprises a rectangular cage member of an open construction dimensioned to fit between adjacent vertebral bodies following surgical removal of the disk. The rectangular cage member includes a plurality of ribs for engaging the plateaus of adjacent vertebral bodies for preventing lateral shifting of the cage. It is held against anterior/posterior motion by a locking screw which threadedly engages the cage and adjacent bone tissue. The cage is adapted to be packed with bone graft material for enhancing solid bone fusion.

Claims

1. An interbody implant for enhancing fusion of adjacent vertebral bodies comprising:

(a) a cage member of generally rectangular cross-section having four mutually perpendicular sidewalls of predetermined height dimension, allowing insertion between adjacent vertebral bodies, and a plurality of parallel, spaced-apart rib members extending between an opposed pair of said four sidewalls, each of said opposed pair of sidewalls including an aperture therethrough of a predetermined diameter; and

(b) a locking screw with threads of a predetermined pitch and a length allowing threaded insertion into said apertures, the locking screw having a root diameter less than said predetermined diameter and a crest diameter greater than the predetermined height dimension of the opposed pair of sidewalls and adapted to threadingly engage the adjacent vertebral bodies when the cage member is inserted between the adjacent bodies and the locking screw is threaded into the apertures in the opposed pair of sidewalls.

2. The interbody implant of claim 1 wherein the plurality of spaced apart rib members project outwardly above and below the opposed pair of sidewalls and adapted to engage the adjacent vertebral bodies for inhibiting lateral displacement of the cage member following implant.

3. The interbody implant of claim 1 wherein the locking screw includes a longitudinal bore and openings of a predetermined size are formed through the locking screw at the roots of said threads for permitting bone growth therethrough.

4. The interbody implant of any one of claims 1-3 wherein the cage member is formed of a material selected from a class consisting of stainless steel, titanium carbon, alloy composites and combinations thereof.

5. The interbody implant of claim 1 wherein the cage member comprises:

(a) first and second cage halves, each having four mutually perpendicular sidewalls of a predetermined height dimension and a plurality of parallel, spaced-apart ribs extending between an opposed pair of sidewalls on each of the first and second halves and with the length and width dimension of the four mutually perpendicular side walls of each of the first and second cage halves being such that the first cage half will fit within the second cage half.

6. The interbody implant as in claim 5 wherein the threaded insertion of the locking screw into the apertures spreads the first and second cage halves apart from one another for altering the effective height dimension of the cage member.

7. The interbody implant of claim 5 wherein the plurality of spaced apart rib members project outwardly above and below the opposed pair of sidewalls and adapted to engage the adjacent vertebral bodies for inhibiting lateral displacement of the cage member following implant.

8. The interbody implant of claim 5 wherein the locking screw includes a longitudinal bore and openings of a predetermined size are formed through the locking screw at the roots of said threads for permitting bone growth therethrough.

9. The interbody implant of any one of claims 5-8 wherein the first and second cage halves are formed of a material selected from a class consisting of stainless steel, titanium carbon, alloy composites and combinations thereof.

10. The interbody implant of claim 1 wherein predetermined ones of the four mutually perpendicular sidewalls include openings formed through a thickness dimension thereof.

11. The interbody implant of claim 5 wherein predetermined ones of the four mutually perpendicular sidewalls include openings formed through a thickness dimension thereof.

12. The interbody implant of claim 1 wherein the cage member comprises:

(a) first and second cage halves, each having a pair of side walls held in parallel spaced relation by a pair of parallel, spaced-apart end walls with the end walls being of a different height dimension, the first cage half having length and width dimensions greater than corresponding dimensions of the second cage half allowing the second cage half to fit within the first cage half and providing a wedge shape to the cage.

13. The interbody implant as in claim 12 wherein the threaded insertion of the locking screw into the apertures spreads the first and second cage halves apart from one another for altering the effective height dimension of the cage member.

14. The interbody implant as in claim 13 wherein the locking screw is frusto-conical in shape.

15. An interbody implant for enhancing fusion of adjacent vertebral bodies comprising:

(a) a cage member having opposed parallel spaced apart front and rear faces and side faces, a generally rectangular cross-section and an open construction, the cage member dimensioned to fit between adjacent vertebral bodies upon surgical removal of an intermediate disk, the cage member including means adapted to engage bone tissue of plateaus of said adjacent vertebral bodies for preventing lateral displacement of the cage member;

(b) an aperture centrally disposed in the front and rear faces; and

(c) a locking screw adapted to be threadedly advanced through the aperture in the front face of the cage member and said bone tissue of said plateaus and into the aperture in the rear face for preventing anterior/posterior displacement of the cage member.

16. The interbody implant of claim 15 wherein the locking screw has a thread root diameter and a thread crest diameter where the thread root diameter is less than a diameter of the aperture and the crest diameter is greater than a height dimension of the cage member.

17. The interbody implant of claim 16 wherein the locking screw is tubular with a longitudinally extending lumen and includes a plurality of apertures extending from the root diameter to the lumen.