ACUTE DISLOCATION OF THE CARPOMETACARPAL JOINT OF THE THUMB - AN ANATOMIC AND CADAVER STUDY

An anatomic study was undertaken to provide an understanding of the li gamentous disruption that occurs during acute dislocation of the thumb carpometacarpal joint. Thirty-eight cadaver thumbs were dissected fre e of soft tissue, with the ligaments preserved. The dorsoradial, poste rior oblique, anterior oblique, and intermetacarpal ligaments were ide ntified in all specimens. A dorsal dislocating force was applied to th e base of the thumb metacarpal to recreate the mechanism of clinical d islocation. Serial sectioning of the ligaments was performed with the metacarpal in neutral, flexion, and extension. The primary restraint t o dorsal dislocation was found to be the dorsoradial ligament, with th e anterior oblique ligament allowing dislocation by subperiosteal stri pping from the base of the first metacarpal. After reduction, the join t was most stable in pronation and extension, which tightened the ante rior oblique ligament. We conclude that the dorsoradial ligament is th e primary restraining force with respect to acute dorsal dislocation o f the thumb carpometacarpal joint.