Silastic ball spacer arthroplasty in the management of hallux valgus and hallux rigidus.

Sixty-two feet in 39 patients who were treated by insertion of a silastic ball spacer prosthesis into the first metatarsophalangeal joint for hallux valgus or hallux rigidus have been reviewed with a follow-up time of between 2 and 6 years. Twenty-one results (34%) were excellent, 27 (43%) were fair, 13 (21%) were poor, and one was revised. Seventeen feet (27%) had some metatarsalgia at followup. Results were disappointing in the young patients; in 19 cases of hallux valgus under the age of 45, 8 were either poor or had been revised. The original concept of the silastic ball spacer was to maintain great toe length and prevent proximal migration of the sesamoids. However 60% of these feet showed settling of the prosthesis or new bone formation around the prosthesis and 54% had more than 2 mm proximal migration of the sesamoid bones. The symptomatic results in these patients were similar to those in whom great toe length had been successfully maintained. The silastic ball spacer infrequently achieves its aims, however maintenance of hallux length does not seem to be important in the symptomatic result.