KNEE OR ELBOW PROSTHESIS

• US 3,868,730 A
• Filed: 02/06/1974
• Issued: 03/04/1975
• Est. Priority Date: 09/24/1973
• Status: Expired due to Term

• Current Assignee: David A. Sonstegard, Herbert Kaufer, Ian P. Murray, Larry S. Matthews
• Original Assignee: David A. Sonstegard, Herbert Kaufer, Ian P. Murray, Larry S. Matthews
• Inventors: Kaufer, Herbert, Matthews, Larry S., Sonstegard, David A., Murray, Ian P.
• Primary Examiner(s): Gaudet, Richard A.
• Assistant Examiner(s): Frinks, Ronald L.
• Application Number:
  US05/440,190
• Time in Patent Office: 391 Days
• Field of Search: 3/1 128/92C,92CA,92R
• US Class Current: 623/20.22
• CPC Class Codes: A61F 2/3854 with ball and socket joint

Abstract

The femoral and tibial components of a knee joint prosthesis are rotatably coupled by a ball and socket connection in which a ball on a connecting rod extending upwardly from the tibial component is engaged up into a high density polyethylene socket insert in the bottom of the femoral component. A pair of spaced substantially parallel spheroidally curved condyle runners straddle the socket opening in the femoral component and have a compound curvature with a larger radius lower portion and a smaller radius upper portion. A slot in the ball retaining socket insert permits the required angular movement of the connecting rod through the angle of flexure, and the connecting rod engages the terminal end of the slot to limit the flexure. The upper edges of the condyle runners are thickened to cause the leading edges of the polyethylene plateau shoes on the tibial component to firmly wedge into them to smoothly arrest flexed tibial movement. The slot is larger than the connecting rod thereby enabling flexure movement, and non-interference with natural rotational and wobbling movement as in a natural knee joint. The concave plateaus substantially correspond with the lower larger radius condyle surfaces to intimately engage them with each other in the extended position for firm extended leg support. The clearance between the plateau and condyle surfaces during flexure is small enough to cause them to interfere after only a slight degree of twisting or wobbling is permitted. This clearance and the associated control of medial and lateral angulation and medial and lateral rotation is maintained by the precise controlled entrapment of the ball in the socket.

Claims

1. A joint prosthesis suitable for a knee or elbow comprising a femoral component, a tibial component, a ball and socket connection coupling said components, said femoral component having a pair of spaced substantially parallel spherodically curved condyle runners straddling a hollow central housing, said condyle runners having a front lower portion with a relatively larger radius of curvature joining a rear upper portion having a relatively smaller radius of curvature as compared to said front lower portion, a slot in the bottom of said housing disposed substantially parallel to said runners, a femoral attaching means in the top of said femoral component, said tibial component having a base, tibial connecting means on the bottom of said base, a pair of spherodially curved spaced parallel concave sliding shoes on said base having upper surfaces substantially corresponding with the front lower portions of said condyle runners for intimately nesting them together when said joint is in the extended position, said ball and socket connection including a connecting rod rigidly fixed to and extending upwardly from said base of said tibial component, the ball of said ball and socket connection being disposed on the upper end of said connecting rod, said hollow central housing enclosing the socket portion of said ball and socket connection disposed for entry through its bottom, said ball portion being rotatably engaged in said socket portion, the smaller radius of curvature of said rear upper portions of said runners providing clearance between said shoes and said rear upper portions in flexed positions of said components, said connecting rod being disposed in said slot which permits said connecting rod to pivot through the angle of flexure of said joint, said connecting rod being narrower than said slot, said clearance between said shoes and said rear upper portions being limited to restrain the twisting and wobbling between interfering portions of said shoes and said runners whereby a natural degree of controlled joint twisting and wobbling is provided.

2. A joint prosthesis as set forth in claim 1, wherein the upper ends of said rear upper portions of said runners slightly protrude radially outwardly for wedging against said shoes whereby the terminal flexure motion of said shoe is smoothly arrested.

3. A joint prosthesis as set forth in claim 1, wherein said ball and socket connection has an axis of rotation, said rear upper portions of said condyle runners having a center of curvature, and said axis of rotation and said center of curvature being coaxial with each other.

4. A joint prosthesis as set forth in claim 1, wherein said runners have a transverse radius of curvature substantially equal to said smaller radius of curvature of said rear upper portions of said condyle runners.

5. A joint prosthesis as set forth in claim 1, wherein said concave shoes have a radius of curvature substantially corresponding to said radius of curvature of said front lower portions of said condyle runners.

6. A joint prosthesis as set forth in claim 5, wherein said concave shoes have a transverse radius of curvature substantially corresponding to the tranSverse radius of curvature of said runners.

7. A joint prosthesis as set forth in claim 1, wherein said tibial connecting means comprises a tibial connecting stem disposed to extend downwardly from said base.

8. A joint prosthesis as set forth in claim 1, wherein said femoral attaching means comprises a femoral attaching stem.

9. A joint prosthesis as set forth in claim 1, wherein said socket portion of said ball and socket connection comprises a slotted insert.

10. A joint prosthesis as set forth in claim 9, wherein said slotted insert comprises high molecular weight polymer.

11. A joint prosthesis as set forth in claim 10, wherein said shoes also comprise high molecular weight polymer.

12. A joint prosthesis as set forth in claim 11, wherein said polymer comprises high density polyethylene.

13. A joint prosthesis as set forth in claim 1, wherein said base includes shoe-containing recesses, said shoes being securely mounted in said recesses.

14. A joint prosthesis as set forth in claim 1, wherein said socket portion of said ball and socket connection comprises a segmented insert, said hollow central housing having an inner cavity, said cavity having overhanging edges on portions of its mouth, said segmented insert being keyed with said overhanging edges whereby said insert may be inserted clear of said overhanging edges in one rotational orientation and interlocked with said edges in another rotational orientation.

15. A joint prosthesis as set forth in claim 14, wherein said keying is constructed and arranged to permit insertion of said insert in only one rotational orientation in said cavity and interlocked in said other rotational orientation of said insert in said cavity.