Effect of Carpometacarpal Joint Osteoarthritis, Sex, and Handedness on Thumb In Vivo Kinematics

Purpose To investigate the influence of trapeziometacarpal (TMC) osteoarthritis (OA) on the 3-dimensional motion capability of the TMC and thumb metacarpophalangeal (MCP) joints. In order to examine other factors affecting the thumb’s motion kinematics, we further aimed to address the influence of sex and handedness on the motion capability of normal TMC and MCP joints. Methods We included 18 healthy subjects (9 women, 9 men; 8 dominant hands, 10 nondominant hands) and 18 women with stage II/III TMC OA. A motion analysis system using surface markers was used to quantify the thumb’s 3-dimensional opposition–reposition kinematics. The range of motion of the thumb’s TMC and MCP joints in flexion–extension, abduction–adduction, and pronation–supination were determined. Results TMC OA led to a loss in abduction–adduction in the TMC joint (38° in controls, 26° in TMC OA subjects), although neither flexion–extension nor pronation–supination were affected. At the MCP joint, the TMC OA subjects showed a 48% reduction in abduction–adduction (32° controls, 16° TMC OA subjects) and 42% reduction in pronation–supination (34° in controls, 20° in TMC OA subjects) than the healthy controls. Ranges of motion of the healthy TMC and MCP joints were similar in dominant and nondominant hands as well as in women and men. Discussion The study demonstrated that stage II/III TMC OA restricts the motion of the TMC joint in abduction–adduction and of the MCP joint in abduction–adduction and pronation–supination. Thumb motion capability was unaffected by sex and handedness. Clinical relevance Osteoarthritis-induced loss of TMC motion did not reflect a generalizable clinical parameter, rather, it seemed to distinctly affect the TMC and the MCP joints and their motion planes and directions. As neither sex nor handedness influenced the motion capabilities of the healthy thumb, kinematic factors contributing to TMC OA may develop at a later age.