Metacarpophalangeal joint arthroplasty in rheumatoid arthritis: results ofSwanson implants and digital joint operative arthroplasty

We discuss 69 metacarpophalangeal (MP) implant arthroplasties performed in 30 patients with rheumatoid arthritis. The follow-up averaged 5 years. We s tudied 19 finger joint prostheses by Condamine, digital joint operative art hroplasty (stabilized version; DJOA) and 50 flexible silicone Swanson impla nts. We used a new comprehensive scoring system to evaluate the MP alloarth roplasties. Such a scoring system incorporates clinical and radiological da ta. The outcome following MP joint replacement with DJOA was never evaluate d as 'good'; in 11 joints the result was 'fair', and in 8 joints, 'poor'. A s regards MP arthroplasty with Swanson implants, the results were evaluated as 'good' in 40 joints, as 'fair' in 10 joints, and in none as 'poor'. In our series, DJOA did not provide stability in arthritic MP joints. In all j oints replaced with DJOA, dislocation of the articulating surfaces and sign s of loosening were present. We regard three factors as being the main caus es contributing to the poor outcome of DJOA when used as MP replacements. F irstly, the proximal prosthetic component is poorly matched to the anatomic al shape of the metacarpal bone (conisation of the bone). Secondly, adequat e coaptation cannot be achieved with this prosthetic design, even in the pr esence of extensive soft-tissue reconstruction. Thirdly, the use of polyeth ylene in MP joint replacements is questionable. In contrast, the silicone S wanson implants in our series provided superior results when used as MP imp lants in the rheumatoid hand.