Abnormal thumb morphology Thumb carpometacarpal subluxation 2025-05-04T15:27:15Z A partial (subluxation) loss of alignment at the base of the thumb, where the first metacarpal bone meets the trapezium bone of the wrist. Thumb radiographs showing carpometacarpal (CMC) joint space widening and/or incongruity of the joint space between thumb metacarpal bone and the trapezium bone. Thumb carpometacarpal dislocation Thumb CMC subluxation