Non-operative treatment of displaced avulsion fractures of the ulnar base of the proximal phalanx of the thumb.

Treatment of displaced or rotated avulsion fractures of the ulnar base of the proximal phalanx of the thumb remains controversial. There is limited information on the outcome of management of these injuries by non-surgical means. We undertook a retrospective follow-up study of the non-operative treatment of these fractures. The study included 28 thumbs that were stable to lateral stress testing at the time of initial investigation. The patients were treated by immobilisation of the thumb in a spica cast. The mean follow-up interval was 2.5 years (range 1-4). None of the patients changed their permanent employment or was unable to participate in their usual sporting activities. Twenty-six patients (93%) reported no pain on movement of the thumb. At follow-up, grip and pinch strengths did not differ significantly on the injured and non-injured sides. No thumbs showed instability on stress testing. The fractures had a 40% rate of bony union and 60% rate of fibrous non-union. All the patients were satisfied with their outcome. None of the patients was operated on after treatment. Non-operative treatment is recommended in cases of displaced or rotated avulsion fractures provided that there is no lateral instability of the metacarpophalangeal joint. Patients with unstable thumbs should always be treated surgically.