Abstract

Carpal boss syndrome, or os styloideum, is characterized by localized tenderness and sharp pain over the junction of the second and third carpometacarpal joints. The pain of carpal boss syndrome results from exostosis of the second and third carpometacarpal joints or, more uncommonly, a loose body involving the intraarticular space. Patients often report that the pain is worse after rigorous physical activity involving the hand rather than during the activity itself. The pain of carpal boss syndrome may also radiate locally, thus confusing the clinical presentation. The disease typically affects the dominant hand, although carpal bossing is present approximately 15% of the time in patients suffering from carpal boss syndrome. Carpal boss syndrome has a slight male predominance and a peak incidence in the middle of the third decade of life. Trauma is often the common denominator in the development of carpal boss syndrome.

On physical examination, the carpal boss appears as a bony protuberance that can be seen more easily by having the patient flex his or her wrist. The pain associated with this action can be reproduced by applying pressure to the soft tissue overlying the carpal boss. Patients with carpal boss syndrome demonstrate a positive hunchback sign; that is, the examiner can appreciate a bony prominence when he or she palpates the carpal boss ( Fig. 59.3 ). Occasionally an inflamed bursa may overlie the bony excrudecence. With acute trauma to the dorsum of the hand, ecchymosis over the carpal boss of the affected joint or joints may be present.