Metacarpal-phalangeal joint arthroplasty of the rheumatoid thumb.

Overview

Fifty patients with rheumatoid arthritis had 59 Swanson implants of the metacarpal-phalangeal joint of the thumb. Eleven patients (15 implants) have since died and only 1 patient (1 implant) has been lost to follow-up leaving 43 implants available for study. The most common preoperative deformity was a boutonniere deformity with a flexible interphalangeal joint. All thumbs had less pain after operation. The average range of active motion is 25 degrees, with a flexion arc from 15 to 40 degrees. There is an average key pinch strength of 4 pounds (range, 0.5 to 10). Improvement in activities of daily living were noted in 40 hands. One thumb required reoperation for instability; the implant was removed and a metacarpal-phalangeal arthrodesis was done. Radiographic progression of disease was noted in only one thumb at the interphalangeal joint and in two other thumbs at the carpometacarpal joint. None of these have required further operations. The maintenance of motion appears to help in activities of daily living as stability and pinch strength are often adequate.