Radial Midcarpal Instability Treated with Radioscaphocapitate Ligament Recession: A Case Report.

 Midcarpal instability is an uncommon entity characterized by pain and clunking as the wrist moves from radial deviation to ulnar deviation. Management is primarily nonoperative. In patients with persistent symptoms, operative treatments are divided into soft tissue reconstruction and limited midcarpal arthrodesis.  We present a rare case of radial midcarpal instability associated with radioscaphocapitate (RSC) ligament injury. A 20-year-old man presented with radial-sided wrist pain and clunking with radial deviation after a fall. Wrist arthroscopy confirmed the pathology of an RSC ligament injury resulting in an extended posture of the scaphoid and a catch-up clunk from sudden flexion of the scaphoid in radial deviation. His RSC ligament was recessed and he had excellent outcome at 1 year follow-up.  Midcarpal instability was reported by Lichtman et al as a painful wrist click in ulnar deviation and classified according to the direction of the subluxation. Radial midcarpal instability was later described by Caputo et al in patients with rotatory subluxation of the scaphoid. We present a previously unreported form of radial midcarpal instability as it does not quite fit into the type III midcarpal instability with ligament laxity of the scaphotrapeziotrapezoid joint and type IV with scapholunate ligament disruption. The painful wrist click occurs in radial deviation as the result of an RSC ligament injury.  We performed arthroscopic thermal capsulorrhaphy of the ulnar arcuate ligaments and dorsal capsule and an open proximal recession of the RSC ligament. The elimination of pain and clunking accompanied by the restoration of scaphoid flexion and return to load-bearing activities validates the pathology and suggests the potential of this soft tissue procedure in the treatment of radial midcarpal instability.