Disc replacement prosthesis

• US 5,928,284 A
• Filed: 07/09/1998
• Issued: 07/27/1999
• Est. Priority Date: 07/09/1998
• Status: Expired due to Term

• Current Assignee: Hamid M. Mehdizadeh
• Original Assignee: Hamid M. Mehdizadeh
• Inventors: Mehdizadeh, Hamid M.
• Primary Examiner(s): Yu, Mickey
• Assistant Examiner(s): STEWART, ALVIN J
• Application Number:
  US09/112,865
• Time in Patent Office: 383 Days
• Field of Search: 623/17, 623/13, 623/18, 623/16, 606/61
• US Class Current: 623/17.13
• CPC Class Codes: A61F 2/441 made of inflatable pockets or chambers filled with fluid, e.g. with hydrogel
• 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 2/4425 made of articulated components
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/30568 Multiple spring systems including two or more helical springs
• CPC Class Codes: A61F 2002/30578 having apertures, e.g. for receiving fixation screws
• CPC Class Codes: A61F 2002/30784 Plurality of holes
• CPC Class Codes: A61F 2002/3085 with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• CPC Class Codes: A61F 2002/443 having two transversal endplates and at least one intermediate component
• 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 2310/00011 Metals or alloys
• CPC Class Codes: Y10S 606/907 Composed of particular material or coated

Abstract

A disc replacement prosthesis is described which is placed within the intradiscal space vacated by a removed deteriorated disc, and which affords mobility rather than fusion between adjacent vertebral bodies. The prosthesis also protects remaining discs from deterioration by providing a shock absorbing prosthesis portion. It adheres initially mechanically to the vertebral bodies and adheres through arthrodesis over a period of time.

Claims

1. A disc replacement prosthesis for positioning between adjacent superior and inferior vertebral bodies in the spine comprising

upper means for contacting and gripping the superior vertebral body lower surface,

lower means for contacting and gripping the inferior vertebral body upper surface,

resilient intermediate means affixed to and extending between said upper and lower means for contacting and gripping,

wherein said upper means comprises an upper cylindrical section, said lower means comprises a lower cylindrical section, and said resilient intermediate means comprises an intermediate cylindrical section, said upper cylindrical section, lower cylindrical section and intermediate cylindrical section forming a cylinder having an exterior surface when joined together, further comprising

screw threads on said exterior surface, the disc replacement prosthesis thereby being configured for positioning and retention between the adjacent superior and inferior vertebral bodies.

2. The disc replacement prosthesis of claim 1 comprising

spring means fixed to and extending between said upper and lower cylindrical sections.

3. The disc replacement prosthesis of claim 2 wherein said spring means comprises

a plurality of coil springs in parallel with said intermediate cylindrical section.

4. The disc replacement prosthesis of claim 1 wherein said intermediate cylindrical section has a channel extending axially therealong configured to receive a prosthesis insertion instrument.

5. The disc replacement prosthesis of claim 1 wherein said intermediate cylindrical section has a channel extending axially therealong, comprising

body compatible elastomeric substance within said channel.

6. The disc replacement prosthesis of claim 1 wherein said upper and lower means for contacting and gripping comprise hydroxy apatite treated metallic members.

7. The disc replacement prosthesis of claim 1 wherein said upper and lower means for contacting and gripping comprise

members having a surface porosity for promoting bone cell growth therewithin.

8. A method of providing a prosthetic replacement for a vertebral disc removed from an intradiscal space between adjacent superior and inferior vertebral bodies, wherein the superior and inferior vertabral bodies are tapped to form screw threads adjacent the intradiscal space, and a disc prosthesis has matching external screw threads thereon, comprising the steps of

fabricating an upper and a lower rigid member having surfaces thereon which are porous to living bone cells,

configuring the upper and lower rigid members for at least temporary retention by the adjacent superior and inferior vertebral bodies respectively,

attaching a resilient member to and between the upper and lower rigid members to produce a disc prosthesis,

engaging the disc prosthesis external screw threads with the vertebral body screw threads, and

turning the disc prosthesis until positioned within the intradiscal space.

9. A prosthesis for replacing a disc removed from an intradiscal space between adjacent superior and inferior vertebral bodies, comprising

an upper prosthesis member having a contact surface configured to engage and become fixed to a lower surface on the superior vertebral body,

a lower prosthesis member having a contact surface configured to engage and become fixed to an upper surface on the inferior vertebral body,

an intermediate elastomeric prosthesis member fixed to and extending between said upper and lower prosthesis members, and

means for securing said upper and lower prosthesis members in place in contact with the superior and inferior vertebral bodies respectively, said upper and lower prosthesis member contact surfaces having a porosity for admitting bone cell growth for enhancing arthrodesis, wherein said upper prosthesis member comprises an upper cylindrical section, said lower prosthesis member comprises a lower cylindrical section and said intermediate elastomeric prosthesis member comprises an intermediate cylindrical section, so that the prosthesis is a cylinder having a cylindrical surface, said means for securing comprising screw threads on said cylindrical surface.

10. The prosthesis of claim 9 wherein said intermediate elastomeric member has an internal chamber, comprising

resilient shock absorbing means within said internal chamber.