summary Thumb CMC Dislocations are rare injuries that occur due to axial force on a flexed thumb. Diagnosis is clinical and can be confirmed by orthogonal radiographs. Treatment is closed reduction and immobilization with unstable injuries requiring surgical stabilization. Epidemiology Incidence makes up <1% of hand injuries Anatomic location Mostly dorsal dislocations login to view 1 more bullet Etiology Pathophysiology mechanism login to view 2 more bullets pathoanatomy login to view 2 more bullets Anatomy Dorsal side ligaments are the primary stabilizers to dorsal/dorsoradial forces 16 total ligaments that stabilize the TMC joint superficial anterior oblique login to view 4 more bullets deep anterior oblique (beak) ligament login to view 1 more bullet dorsoradial ligament login to view 4 more bullets posterior oblique ligament ulnar collateral ligament intermetacarpal ligament dorsal intermetacarpal dorsal trapeziotrapeziod volar trapeziotrapeziod dorso trapezio-II metacarpal volar trapezio-II metacarpal trapezio-III metacarpal transverse carpal ligament trapeziocapitate volar scaphotrapezial radial scaphotrapezial 7 main stabilizers of TMCJ – SAOL, dAOL, DRL, POL, UCL, IML and DIML 9 stabilizers of trapezium – DTT, VTT, DT-II MC, VT-II MC, T-III MC, VST, RST, trapeziocapitate and transverse carpal 4 key ligamentous restraints of the thumb anterior oblique ligament login to view 1 more bullet posterior oblique ligament intermetacarpal ligament dorsoradial ligament login to view 1 more bullet Presentation History collide onto fixed object/axial force on a flexed thumb dorsal force applied to 1st web space login to view 1 more bullet Symptoms pain over thenar eminence Physical exam swelling, bruising over thenar eminence unable to form a fist Imaging Radiographs recommended views login to view 2 more bullets optional views login to view 2 more bullets findings login to view 2 more bullets MRI indications login to view 2 more bullets Diagnosis Radiographic diagnosis confirmed by history, physical exam, and radiographs Treatment Nonoperative closed reduction and immobilization in extension and pronation login to view 2 more bullets Operative closed reduction and temporary pinning reconstruction of the dorsal capsuloligamentous complex with tendon autograft + temporary pinning login to view 5 more bullets Complications Anterior osteophyte often visible Low incidence of recurrent dislocation