Midcarpal Instability


Palmar midcarpal instability is characterized by kinematic dysfunction of the proximal carpal row, and is often associated with a painful ulnar catch-up "clunk" as the wrist moves from radial to ulnar deviation. Clinical and laboratory findings suggest that palmar midcarpal instability is caused by a functional loss of midcarpal constraints, primarily the dorsal radiotriquetral (dorsal radiocarpal) ligament and the ulnar arm of the palmar arcuate ligament, which permits hypermobility of the proximal carpal row. The midcarpal shift test is diagnostic when the test recreates the painful clunk. When nonsurgical management fails, surgical options include extensor carpi ulnaris reconstruction, dorsal capsular reefing, arthroscopic thermal capsulorrhaphy, and limited midcarpal arthrodesis. Although much has been learned about the kinematics of wrist instability, there remains much opportunity for future clinical and biomechanical research, with the goal of developing better surgical and nonsurgical techniques that produce more successful patient outcomes.

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