Replacement of the os trapezium by polyurethane implants.

Twenty-five patients with arthrosis of the first carpometacarpal joint had the os trapezium replaced by a polyurethane implant (Tecoflex), and the results were evaluated after three years (range 28-47 months). There were three failures in which the implants had been removed because of dislocation with pain. The clinical results in the remaining 22 cases in terms of relief of pain and thumb function were comparable with previous series of silicone implants. Radiographic examination showed no signs of bone resorption or other unfavourable tissue reactions around the implants, but subluxation of the implants was seen in half of the cases. Implant subluxation might be caused by poor design of the implant or the limited amount of fibrous foreign-body reaction around the polyurethane material that resulted in less firm encapsulation than occurred around silicone implants.