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[Results of the ARPE trapezometacarpal prosthesis: a retrospective study of 37 cases].

We report the outcome of the ARPE trapezometacarpal prosthesis in the treatment of primary osteoarthritis of the thumb. The prosthesis based on a ball and socket system and is uncemented. This study presents the results of 37 consecutive implantations in 29 patients; 28 women, one man, eight bilateral (21 right, 16 left). The mean age at operation was 67 years at a mean of 36 months follow-up (maximum 7 years). Four patients were excluded (1 died, 3 lost to follow up). Preoperative radiological grading according to Comtet was 1 or 2. Patients all had low functional demand. Most of the patients were satisfied and pain free. Mobility was increased, including dorsal extension of the first metacarpal. Radiographic analysis and measurement of the scaphometacarpal index demonstrated a postoperative increased length of the thumb column, with a slight decrease at follow up. This phenomenon is due to sinkage of the prothesis into the cancellous bone. Mechanical complications occurred in four patients within the first four years. Removal of the prosthesis, trapeziectomy and tendon strip plasty were performed in three cases with good final results. This prothesis is a good surgical treatment of primary, isolated TM osteoarthritis in patients with minimal osteoporosis and low functional demands.