Interbody fusion device and method for restoration of normal spinal anatomy

• US 5,782,919 A
• Filed: 03/27/1995
• Issued: 07/21/1998
• Est. Priority Date: 03/27/1995
• Status: Expired due to Term

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: SDGI Holdings Incorporated (Medtronic Plc)
• Inventors: Boyd, Lawrence M., Zdeblick, Thomas, Ray, Eddie III
• Primary Examiner(s): ISABELLA, DAVID J
• Application Number:
  US08/411,017
• Time in Patent Office: 1,212 Days
• Field of Search: 623/16, 623/17, 623/18, 606/61
• US Class Current: 623/17.16
• CPC Class Codes: A61B 17/1671 for the spine
• CPC Class Codes: A61B 17/8883 the driver bit acting on the periphery of the screw head
• CPC Class Codes: A61B 17/8891 at its periphery
• CPC Class Codes: A61F 2/30744 End caps, e.g. for closing an endoprosthetic cavity
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• 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 2/4455 for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• 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 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2/4637 for connecting or disconnecting two parts of a prosthesis
• 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 2002/30136 undulated or wavy, e.g. serpentine-shaped or zigzag-shaped
• CPC Class Codes: A61F 2002/30143 hexagonal
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30158 trapezoidal
• CPC Class Codes: A61F 2002/3021 frustoconical
• CPC Class Codes: A61F 2002/30217 hollow cones, e.g. tubular-like cones
• CPC Class Codes: A61F 2002/305 Snap connection
• CPC Class Codes: A61F 2002/30593 hollow
• CPC Class Codes: A61F 2002/30774 internally-threaded
• CPC Class Codes: A61F 2002/30777 : Oblong apertures
• CPC Class Codes: A61F 2002/30785 : parallel
• CPC Class Codes: A61F 2002/3082 : Grooves
• CPC Class Codes: A61F 2002/3085 : with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• CPC Class Codes: A61F 2002/30858 : Threads interrupted by grooves or sidewalls, e.g. flat sidewalls
• CPC Class Codes: A61F 2002/30873 : Threadings machined on non-cylindrical external surfaces
• CPC Class Codes: A61F 2002/448 : comprising multiple adjacent spinal implants within the same intervertebral space or within the same vertebra, e.g. comprising two adjacent spinal implants
• CPC Class Codes: A61F 2002/4641 : for disconnecting
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0004 : Rounded shapes, e.g. with rounded corners
• CPC Class Codes: A61F 2230/0017 : Angular shapes
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0026 : trapezoidal
• CPC Class Codes: A61F 2230/0067 : conical
• 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 2310/00095 : Niobium or Nb-based alloys
• CPC Class Codes: A61F 2310/00131 : Tantalum or Ta-based alloys
• CPC Class Codes: A61F 2310/00161 : Carbon; Graphite
• CPC Class Codes: A61F 2310/00179 : Ceramics or ceramic-like structures
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite
• CPC Class Codes: A61L 2430/38 : for reconstruction of the spine, vertebrae or intervertebral discs
• CPC Class Codes: A61L 27/227 : Other specific proteins or polypeptides not covered by A61L27/222, A61L27/225 or A61L27/24
• CPC Class Codes: A61L 31/047 : Other specific proteins or polypeptides not covered by A61L31/044 - A61L31/046

Abstract

An interbody fusion device includes a tapered body defining a hollow interior for receiving bone graft or bone substitute material. The body defines exterior threads which are interrupted over portions of the outer surface of the device. The fusion device defines truncated side walls so that on end view the body takes on a cylindrical form. The side walls are provided with vascularization openings, and the body wall device includes opposite bone ingrowth slots extending through the interrupted thread portion of the body. An implant driver is provided which engages the truncated side walls to complete the cylindrical form of the implant at the root diameter of the interrupted threads. The driver facilitates threaded insertion of the implant to the intra-discal space between adjacent vertebrae. The implant is tapered at a predetermined angle generally corresponding to a desired lordotic angle of the spine. The implant is inserted to a determinant depth into the intra-discal space to restore the normal lordosis of the particular vertebral level. The lordotic angle is restored not only by way of the taper of the implant itself, but also as a function of the depth of insertion of the implant into the space. The implant is readily adapted for insertion from either an anterior or a posterior approach. In the anterior approach, the implant is screw threaded into position, while in the posterior approach the implant operates as a cam to spread the vertebral bodies apart to an appropriate lordotic angle.

Claims

1. A fusion device for facilitating arthrodesis in the disc space between adjacent vertebrae, comprising:

an elongated body having a length between a first end and a second end thereof, and a first diameter at said first end sized to be greater than the space between the adjacent vertebrae, said body further defining a hollow interior sized to receive bone growth promoting material therein;

said body having an outer surface with a pair of opposite cylindrical portions extending along substantially the entire length of said body and defining said first diameter, and a pair of substantially flat opposite side walls connected between said opposite cylindrical portions, said side walls extending along a substantial portion of said length of said body; and

external threads defined on said pair of opposite cylindrical portions of said outer surface and extending along substantially the entire length of said body.

2. The fusion device according to claim 1, wherein said cylindrical portions are tapered along a substantial portion of said length and define a second diameter at a second end thereof that is greater than said first diameter.

3. The fusion device of claim 1, further comprising a number of openings defined in said opposite side walls for communicating with said hollow interior.

4. The fusion device of claim 3, further comprising a pair of diametrically opposed slots defined through said threads in said cylindrical portion and communicating with said hollow interior, said opposed slots being elongated along said length of said body and each being larger than the combination of said number of openings.

5. The fusion device of claim 1, further comprising a pair of diametrically opposed slots defined through said threads in said cylindrical portion and communicating with said hollow interior, said opposed slots being elongated along said length of said body.

6. The fusion device of claim 5, wherein said opposed slots are rectangular in configuration and have a width dimension transverse to said length of said body;

and

said cylindrical portions define an effective width between said opposite side walls and said opposed slots,

wherein said width dimension of said opposed slots is greater than said effective width of said cylindrical portions.

7. The fusion device of claim 1, wherein:

said flat side walls terminate near said first end; and

said cylindrical portions and said threads are interrupted by said side walls and are circumferentially continuous thereafter from said side walls to said first end.

8. The fusion device of claim 1, wherein said body is closed at said first end and is open to said hollow interior at a second end opposite said first end.

9. The fusion device of claim 1, wherein said body includes a second end opposite said first end, said second end being open to said hollow interior.

10. The fusion device of claim 7, wherein:

said body includes a second end opposite said first end; and

said flat side walls terminate at said second end.

11. The fusion device of claim 10, wherein said opposite side walls each define a notch at said second end configured to receive a driving tool for implanting said device.

12. A fusion device for facilitating arthrodesis in the disc space between adjacent vertebrae, comprising:

an elongated body having a length, a first diameter at a first end and a larger second diameter at a second end opposite said first end, said first and second diameters sized to be greater than the space between the adjacent vertebrae, said body further defining a hollow interior sized to receive bone growth promoting material therein;

said body having an outer surface that is substantially continuously tapered from said first end to said second end with external threads defined on said outer surface and extending substantially entirely along said length of said body.

13. The fusion device of claim 12, further comprising a pair of diametrically opposed slots defined through said threads in said outer surface and communicating with said hollow interior, said opposed slots being elongated along said length of said body.

14. The fusion device of claim 12, wherein said body is closed at said first end and is open to said hollow interior at said second end.