The authors reporte a case of delayed, static, palmar mid-carpal instability in a healthy 39 year-old woman who fell and landed heavily on the dorsum of her flexed wrist. Initial radiographs showed normal carpal bone alignment. A thumb-spica cast was applied for treatment of a suspected scaphoid fracture: a volar lip avulsion fracture of the lunate was eventually diagnosed. Radiographs 6 weeks post-injury demonstrated VISI, and radiographs 6 months later showed volar dislocation of the lunate with degenerative changes. Surgery was eventually undertaken, involving a scaphoid excision and four-corner arthrodesis.
Palmar midcarpal instability has been associated with injury to the following wrist ligaments: radioscaphocapitate, triquetrohamate, triquetrocapitate, and dorsal radiocarpal. The lunate fracture in this case was assumed to represent a destabilizing soft-tissue injury. Other instability patterns may be recognized in a delayed fashion following wrist sprains and fractures (Doig et al, Injury 1991; Forward et al, JBJS Am 2007). These instability patterns are not always obvious, the incidence rates are not known, and proposed treatments are varied.
Wrist, Instability, Midcarpal, Dislocation