Instability of the prosthesis and silicone-induced synovitis have led most surgeons to abandon use of the Swanson trapezium implant for the treatment of primary osteoarthritis. However, the literature contains little information on the results of long-term follow-up. The present study was conducted to establish the long-term results and to highlight the problems associated with the implant.
Thirty-five patients (forty-five implants) of our initial forty-five patients (fifty-seven implants) were available for clinical review. The mean duration of follow-up was 13.8 years. The objective result was assessed with a 40-point clinical scoring system. The subjective result was measured with a visual analog scale. A clinical score of 30 to 40 points and a subjective score of 8, 9, or 10 points were considered a good-to-excellent result. Radiographs were evaluated to determine the position and deformation of the prosthesis and to check for osteolytic changes of the bone, indicating silicone-induced synovitis.
The overall clinical and subjective results were good for twenty-seven thumbs (60%). Eighteen thumbs (40%) had a dislocation, and nine of them had a revision. Three more revisions were carried out because of silicone-induced synovitis, persistent pain after reflex sympathetic dystrophy, and deep infection in one thumb each. Revision surgery consisted of resection of the implant, with or without tendon interposition, or implantation of a new prosthesis. Of the thirty-two prostheses (thirty that had not been revised and two that had been revised) for which follow-up radiographs were available, six (19%) showed wear and deformation and five (16%) also were associated with osteolytic changes.
The main problem associated with the prosthesis was dislocation. Surgical measures to improve stability did not prevent this complication. The results after revision because of dislocation were no better than those associated with unrevised dislocated implants. In addition to dislocation, radiographic signs of silicone-induced synovitis were frequently noted, although they did not necessarily lead to a poor result. We concluded that the results after long-term follow-up of the Swanson silicone trapezium implant for the treatment of primary osteoarthritis were poor and that our decision to stop using this implant in 1991 was correct.