Poor experience with a hinged endoprosthesis (WEKO) for the metacarpophalangeal joints: all 28 prostheses removed within 2 years in 8 patients having rheumatoid arthritis

We prospectively assessed the outcome of implanting a hinged prosthesis in destroyed metacarpophalangeal (MCP) joints (Larsen stage III-V). We implanted 28 cementless, axis-coupled total endoprostheses with hinging (WEKO prosthesis, Implant-Service GmbH, Hamburg, Germany) in 8 women (mean age 62 (47-80) years) suffering from rheumatoid arthritis. The mean follow-up period was 15 (12-18) months, and the evaluation was based on objective criteria, including joint motion, ulnar deviation of the long fingers, grip strength, radiographic migration and torsion of the prostheses, as well as the patients' subjective satisfaction. 12 months postoperatively, the mean arc of flexion was 30 (22-35) degrees, and the mean extension lag was 43 (40-48) degrees. Although no ulnar deviation was seen in 2 fingers, it was < 10 degrees in 3, between 10 degrees and 20 degrees in 7 of the fingers, and more than 20 degrees in 16. None of the patients could clench their fist firmly. We found prosthesis migration in 20 and torsion in 19 fingers. 2 years postoperatively, we had to remove all of the prostheses due to functional failure.