Elbow joint prostheses

Abstract

A radial head assembly is provided that includes a stem, a collar, a locking ring, and an articular member. The stem has a convex articular head on one end thereof. The locking ring has a ring wall, which has a ring opening. The ring wall has an angular outer surface and a slot configured to permit the ring wall to radially expand. The angular outer surface engages an angular portion of an interior surface of the collar. The articular member and the locking ring define an articular space within the collar. The articular space is configured to receive the convex articular head.

What is claimed is: 
     
         1 . A surgical method comprising:
 attaching a distal portion of a stem to a first bone, the stem comprising an articular head on a proximal end of the stem;   placing an opening of an articular assembly on the articular head, wherein the articular assembly comprising:
 a concave surface disposed on the articular assembly opposite the opening to face a second bone opposite the first bone, a collar defining the opening, a space extending from the opening into the interior of the articular assembly, and an interior trapping surface proximate to the opening; and 
 a trapping member disposed in the opening; 
   expanding the trapping member; and   advancing the articular head through the trapping member such that the articular head is disposed between the trapping member and the concave surface and the trapping member is disposed between the articular head and the interior trapping surface.   
     
     
         2 . The method of  claim 1 , wherein the trapping member comprises a ring extending between two free ends, the free ends having a gap therebetween, and expanding the trapping member comprises pressing the articular head against the trapping member to expand the gap disposed between the free ends of the ring. 
     
     
         3 . The method of  claim 1 , further comprising applying a distraction force between the stem and the articular assembly to press a mating surface of the trapping member against the interior trapping surface. 
     
     
         4 . The method of  claim 1 , further comprising applying a compressive force between the concave surface and the collar to press a mating surface of the trapping member against the interior trapping surface. 
     
     
         5 . The method of  claim 1 , wherein the first bone is a radius, the second bone is a humerus, and attaching the distal portion of the stem comprises attaching the distal portion of the stem to an end of the radius adjacent to the humerus, and further comprising attaching a humeral articular component to the humerus and articulating the concave surface of the articular assembly against the humeral articular component. 
     
     
         6 . The method of  claim 1 , further comprising disengaging the trapping member from the interior trapping surface, expanding the trapping member, and withdrawing the articular head the opening of the articular assembly. 
     
     
         7 . A kit comprising:
 a radial head assembly that comprises:
 a stem comprising a convex articular head on one end thereof; 
 a collar comprising a collar wall defining a first collar opening, a second collar opening, an internal space between the first collar opening and the second collar opening, and a passage therethrough, the collar wall having an interior collar surface comprising an angular portion proximate to the first collar opening; 
 a locking ring comprising a ring wall defining a ring opening, the ring wall having an angular outer surface and a slot configured to permit the ring wall to radially expand, the angular outer surface engaging the angular portion of the interior collar surface, wherein the locking ring further comprises a flange configured to engage the first collar opening and inhibit disengagement of the locking ring from the collar, the locking ring being positionable in the internal space in a first position in which the flange is spaced away from the first collar opening and in a second position in which the flange spans the opening to cause the locking ring to be securely retained in the first collar opening; 
 an articular member comprising:
 a base having an outer rim and a first concave surface; and 
 a projection extending from the base, the projection comprising a second concave surface disposed between the first concave surface and an end of the articular member opposite the first concave surface, the projection having a peripheral surface configured to engage the interior collar surface; 
 
   wherein the articular member and the locking ring define an articular space within the collar, the articular space configured to receive the convex articular head; and   a tool configured to enable the locking ring to move between the first position and the second position.   
     
     
         8 . The kit of  claim 7 , wherein the tool comprises a locking tool having a distal end configured to apply a compressive force between the collar and the locking ring to enable the locking ring to move from the first position to the second position. 
     
     
         9 . The kit of  claim 7 , wherein the tool comprises a removal tool having a distal end with a projection configured to be inserted through the aperture to compress the locking ring to enable the locking ring to move from the second position to the first position. 
     
     
         10 . An articular assembly comprising:
 an articular member comprising a concave surface to face a second bone opposite a first bone; and   an articular portion configured to couple with a stem coupled with a first bone, the articular portion comprising:
 a collar comprising a collar wall defining a collar opening adjacent to the concave surface and an interior trapping surface proximate to the collar opening; 
 a space extending from the collar opening into an interior of the collar; and 
 a trapping member comprising a trapping member opening and a mating surface configured to engage the interior trapping surface; 
   wherein the articular assembly has a configuration in which the interior trapping surface engages the mating surface to prevent the trapping member from expanding such that a head member coupled with the concave surface and disposed in the articular space can be retained in the articular space.   
     
     
         11 . The articular assembly of  claim 10 , wherein the opening in the collar wall is a first opening, the collar wall further defining a second opening opposite the first opening, the second opening configured to receive a head portion of a stem. 
     
     
         12 . The articular assembly of  claim 10 , further comprising a stem configured to be engaged with a radius forming part of an elbow joint. 
     
     
         13 . The articular assembly of  claim 12 , wherein the articular portion includes a projection having a peripheral wall configured to engage an interior of the wall of the collar to secure the projection to the collar, the projection having a second concave surface on an end portion facing the second bone. 
     
     
         14 . The articular assembly of  claim 13 , wherein the head member comprises a convex surface configured to articulate on the second concave surface of the projection. 
     
     
         15 . The articular assembly of  claim 13 , wherein the projection and the collar are configured to provide a press-fit engagement when the peripheral wall is engaged with the interior wall. 
     
     
         16 . The articular assembly of any one of  claim 10 , wherein the collar further comprises an aperture configured to facilitate disengagement of the trapping member from the collar.