Intervertebral spacer device having a radially thinning slotted belleville spring

• US 6,740,117 B2
• Filed: 10/01/2001
• Issued: 05/25/2004
• Est. Priority Date: 02/15/2001
• Status: Expired due to Fees

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: Spinecore, Inc. (Stryker Corporation)
• Inventors: Ralph, James D., Tatar, Stephen
• Primary Examiner(s): Snow, Bruce
• Assistant Examiner(s): Pellegrino, Brian E
• Application Number:
  US09/968,045
• Publication Number:
  US 20020111681A1
• Time in Patent Office: 967 Days
• Field of Search: 623/17.11, 623/17.13, 623/17.14, 623/17.15, 623/17.16, 411/12, 411/155, 411/156, 411/261
• US Class Current: 623/17.14
• CPC Class Codes: A61F 2/30742 Bellows or hose-like seals; Sealing membranes A61B17/8808 takes precedence; sealing membranes for retaining bone substitute A61F2/2846
• 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 2/4425 made of articulated components
• CPC Class Codes: A61F 2002/30171 rosette- or star-shaped
• CPC Class Codes: A61F 2002/302 toroidal, e.g. rings
• CPC Class Codes: A61F 2002/30331 made by longitudinally pushing a protrusion into a complementarily-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2002/30433 using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30451 soldered or brazed or welded
• CPC Class Codes: A61F 2002/30492 using a locking pin
• CPC Class Codes: A61F 2002/305 Snap connection
• CPC Class Codes: A61F 2002/30507 using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/30518 with possibility of relative movement between the prosthetic parts
• CPC Class Codes: A61F 2002/30538 for adjusting angular orientation
• CPC Class Codes: A61F 2002/30563 having elastic means or damping means, different from springs, e.g. including an elastomeric core or shock absorbers
• CPC Class Codes: A61F 2002/30565 having spring elements
• CPC Class Codes: A61F 2002/30571 Leaf springs
• CPC Class Codes: A61F 2002/30594 slotted, e.g. radial or meridian slot ending in a polar aperture, non-polar slots, horizontal or arcuate slots
• CPC Class Codes: A61F 2002/30604 modular
• CPC Class Codes: A61F 2002/30649 Ball-and-socket joints
• CPC Class Codes: A61F 2002/30769 : madreporic
• CPC Class Codes: A61F 2002/30774 : internally-threaded
• CPC Class Codes: A61F 2002/30909 : Nets
• CPC Class Codes: A61F 2002/3092 : having an open-celled or open-pored structure
• CPC Class Codes: A61F 2002/30975 : made of two halves
• CPC Class Codes: A61F 2002/443 : having two transversal endplates and at least one intermediate component
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0033 : made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2220/0041 : using additional screws, bolts, dowels or rivets, e.g. connecting screws
• CPC Class Codes: A61F 2220/0058 : soldered or brazed or welded
• CPC Class Codes: A61F 2230/005 : Rosette-shaped, e.g. star-shaped
• CPC Class Codes: A61F 2230/0065 : toroidal, e.g. ring-shaped, doughnut-shaped
• CPC Class Codes: A61F 2250/0006 : for adjusting angular orientation
• 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 2310/00365 : Proteins; Polypeptides; Degradation products thereof

Abstract

An intervertebral spacer device having a pair of opposing plates for seating against opposing vertebral bone surfaces, separated by at least one spring mechanism. A first plate of this embodiment includes a post extending upwardly from the inner surface of the plate, the post including a ball-shaped head. The post is designed to flexibly support a slotted belleville washer, which can be selectively mounted to the head such that the wider portion of the washer seats against the second plate. Compression of the assembly causes a deflection of the slotted belleville washer. The slotted belleville washer of this invention has a radially varying thickness which permits the load deflection profile to mimic that of the natural cartilage which is being replaced.

Claims

1. An intervertebral spacer device comprising:

first and second plate members, each having an outwardly facing plate surface and an inwardly facing plate surfaces thereof, said plate members being disposed in a spaced apart relationship such that the inwardly facing ones of said plate surfaces oppose one another, and the outwardly facing ones of said plate surfaces face in opposite directions, the inwardly facing plate surface of the first plate member having a central post structure extending therefrom, the post structure having a ball-shaped head that is inwardly directed toward the second plate member; and

at least one convex housing element disposed between the inwardly facing plate surfaces of said first and second plate members such that a wide end of the convex housing element faces the inwardly facing plate surface of the second plate member, the convex housing element having a curvate volume at a narrow end of the convex housing element;

wherein

the ball-shaped head is captured in the curvate volume, with the curvate volume accommodating the ball-shaped head for rotation and angulation of the ball-shaped head in the curvate volume about a central portion of the ball-shaped head; and

wherein

the inwardly facing plate surface of the second plate member includes a wall for limiting movement of the wide end of the convex housing element along the inwardly facing plate surface of the second plate member, in that the wide end of the convex housing element is disposed with the wide end adjacent the wall and said movement along the inwardly facing plate surface of the second plate member is limited by interterence between the wide end and the wall, and wherein

the inwardly facing plate surface of the second plate member further includes a ring for limiting movement of the wide end of the convex housing element away from the inwardly facing plate surface of the second plate member, in that the wide end of the convex housing element is disposed adjacent the ring and said movement away from the inwardly facing plate surface of the second plate member is limited by interference between the wide end and the ring.

2. The device as set forth in claim 1, wherein the convex housing element comprises at least one slotted belleville washer having a radially varying thickness.

3. The device as set forth in claim 2, wherein the at least one slotted belleville washer having said radially varying thickness is thicker at the inner portion of the washer as compared with the outer portion.

4. The device as set forth in claim 2, wherein the at least one slotted belleville washer having said radially varying thickness is thicker at the outer portion of the washer as compared with the inner portion.

5. The device as set forth in claim 2, wherein said radially varying thickness of the at least one slotted belleville washer varies continuously.

6. The device as set forth in claim 2, wherein said slotted belleville washer comprises a plurality of spaced apart spiral slots, each of which extend from a locus on a peripheral edge of the at least one slotted bellevilie washer to a locus which is radially in from said peripheral edge.

7. The device as set forth in claim 2, wherein said post structure further includes a threaded bore which extends axially from said ball-shaped head toward said inwardly facing plate surface of said second plate member, and which bore receives therein a threaded set screw such that prior to insertion of the set screw therein, said bore permits the ball-shaped head to compress radially inwardly, and such that after the insertion of said set screw said ball-shaped head is not readily radially compressible.