The authors propose a scaphotrapeziotrapezoidal (STT) arthroplasty using a discoid pyrocarbon implant. The aim of this prosthesis is to restore the scapho-trapezial mobility without destabilising the carpal bones (unlike with a simple resection of the distal scaphoid pole).
This technique was used in 15 cases from 1994 to 2002. 12 patients (10 females and 2 males), mean age 65 years) have been reviewed with a mean follow-up of 4 years (1 to 8). Surgical indication was pain refractory to medical treatment (average 8.5 on V.A.S.). Pre-operative mobility showed a loss of radial deviation and dorsal flexion. The severity of the pain did not allow evaluation of the pre-operative strength. Post-operative results were assessed with the EVAL computerised system, static and dynamic X rays were performed in all cases.
Pain decreased to an average of 2. The mobility compared to the healthy side showed a slight loss of radial deviation (less than 10 degrees) and in wrist extension (less than 15 degrees). Grip strength was similar to the normal side, even during rapid exchanges. Pinch grip evaluation showed a slight decrease (0.8 kg) which did not compromise normal function of the first ray. No implant luxation was observed in the radiological study. Angular measurements did not show any modification in DISI and other static angles remained unchanged. Dynamic sagital and frontal views confirmed the good mobility of the prosthesis which adjusts its position to the scaphoid movements.
The good results, the simple surgical procedure, the absence of complications, the lack of a need for any fixation or ligamentoplasty all confirm the advantages of this pyrocarbon implant in the treatment of STT arthrosis. Furthermore, in cases of failure, it is possible to use any other revision procedure.