Silastic interposition arthroplasty for osteoarthrosis of the carpometacarpal joint of the thumb.

We performed Ashworth's (1977) silastic interposition arthroplasty for painful osteoarthrosis of the carpometacarpal (CM) joint of the thumb. Recently, however, some unsuccessful cases treated by this method have been reported. We therefore reviewed the results of patients treated by Ashworth's method. We reviewed 16 patients operated on according to the original Ashworth method for osteoarthrosis of the first CM joint. The cases consisted of 8 males and 8 females, ranging in age from 32 to 76 years (average, 59.6 years). The patients were grouped according to Eaton's classification as follows: 1 patient was stage II, 6 were stage III, and 9 were stage IV. All patients were followed postoperatively for 1 to 12.5 years (average, 4.5 years). Twelve patients did not complain of any pain but 3 patients felt slight pain when moving their thumb. However, the degree of pain was much less than that experienced preoperatively. Only one patient complained of severe pain 2 years after the first operation. Her implant ruptured and required additional surgery. All except one showed either an increase or no change in grip strength. The range of motion (ROM) was full in all patients. Implants showed sinking in 3 patients, a partial rupture of the implant edge in 5 patients and a whole body failure in only 1 implant, roentogenographically. In spite of these troubles, only 3 patients complained of an unpleasant feeling and 2 reported slight pain. Implant trouble did not always cause the symptoms. The clinical results of this method were mostly satisfactory.