Silicone rubber replacement of the severely fractured radial head.

Ten patients, at an average of 3.4 years after Swanson silicone rubber radial head replacement following acute trauma, were evaluated for pain, motion, and grip strength. Three had excellent results, one had a fair result, and two had poor results. Three patients had arthritis at the distal radioulnar joint. The arthritis was correlated with a positive ulnar variance in the uninjured wrist. Degenerative arthritis at the elbow was present in 56% (five out of nine). Ulnar variance was increased significantly in the wrists on the injured side, compared with the opposite wrist and to a control group. A 20-kg grip stress radiograph analysis showed the silicone rubber prostheses to deform and wrist subluxation to occur. A biomechanical study of six human cadaver upper extremities indicated that the flexible implants transferred minimal forces across the radiocapitellar joint. A radial head replacement with a modulus of elasticity similar to bone showed a more physiologic loading at the elbow. Both the clinical and biomechanical studies indicated that the silicone rubber prostheses is unable to transmit physiologic forces from the proximal radius to the capitellum. A less flexible radial head prosthesis should provide more normal physiologic stresses and may lead to improved clinical results.