Spontaneous ruptures of flexor tendons secondary to extreme DISI deformity of the lunate in a rheumatoid wrist. A case report.

Spontaneous flexor tendon ruptures in rheumatoid arthritis are associated with flexor tenosynovitis and/or with attrition due to bony prominences in the carpal tunnel. The commonest bony prominence observed is the distal pole of a rotated scaphoid. We are reporting the case of an eighty-year-old woman with long-standing rheumatoid arthritis who presented with the inability to actively flex both the interphalangeal and the metacarpophalangeal joints of the right index finger, with preservation of passive motion. There was also loss of active flexion of the interphalangeal joint of the right thumb. Roentgenograms revealed a marked dorsal intercalated segment instability (DISI) pattern in both wrists associated with advanced joint destruction and collapse. Surgical exploration revealed total rupture of the FDS and FDP of the index finger and of the FPL, as well as partial rupture of the flexor tendons of the long finger. Rupture of the FPL was found to be due to attrition on the relatively common finding of a prominent and malrotated scaphoid. Ruptures of the flexor tendons of the index and long fingers appeared to be caused by a markedly prominent palmar protrusion of the lunate. Surgical repair was undertaken, including correction of the DISI deformity and reconstruction of carpal height by radiolunate fusion from a palmar approach. In addition the tubercle of the scaphoid was resected, and the FDS tendon of the ring finger was transferred to the distal stump of the FDP of the index finger; the FPL tendon was not reconstructed as arthrodesis of the interphalangeal joint of the thumb was planned at a later date.(ABSTRACT TRUNCATED AT 250 WORDS)