Motion deficit of the thumb in CMC joint arthritis

Purpose: Idiopathic osteoarthritis (OA) of the thumb carpometacarpal (CMC) joint is a common disabling disease that often causes pain and motion loss. The aims of this study were to characterize the multidimensional motion capability of the thumb CMC joint in a group with severe CMC OA and to compare it with a control group. Methods: We included 15 subjects with stage III/IV CMC OA according to the Eaton/Littler classification, and 15 control subjects. A motion analysis system using surface markers was employed to quantify the maximum boundary of the thumb circumduction envelope during repetitive thumb movements. We measured the area enclosed by the angular circumduction envelope and the ranges of motion (ROM) in multiple directions for the thumb CMC joint. Results: Thumb osteoarthritis of the CMC joint stage III/IV resulted in a significantly smaller ROM in flexion/extension (45° ± 11° for the CMC OA group, 59° ± 10° for the controls), abduction-adduction (37° ± 6° for the CMC OA group, 63° ± 13° for the controls), and pronation-supination (49° ± 10° for the CMC OA group, 62° ± 11° for the controls) (p < .01). When analyzing the motion directions in flexion-extension and abduction-adduction separately, there was only a loss of extension and adduction (p < .01). Conclusions: Severe stages of thumb CMC OA cause an asymmetrical motion deficit with decreased ROM in extension and adduction, leading to decreased capability of counteropposition.