Operational and maximal workspace of the thumb.

The purposes were to examine the workspace of the thumb during its operational (submaximal and random) movement and to compare the operational workspace with its maximal workspace. Fifteen female subjects with asymptomatic hands performed the thumb circumduction and operational motion. Linear and angular measurements of the thumb were obtained by a marker-based motion analysis system. During the circumduction, the linear ranges of motion of the thumb tip were 102.8 +/- 9.9 mm and 130.7 +/- 14.1 mm in abduction/adduction and flexion/extension directions, respectively, and the corresponding values for the operational motion were 67.3 +/- 16.1 mm and 73.1 +/- 18.0 mm, respectively. The angular ranges of motion of the carpometacarpal (CMC) and metacarpophalangeal joints during the operational motion were less than 65% of their maximal motion ranges. In addition, the CMC joint tended to move in directions oblique to its anatomical defined axes. The results of operational motion may provide guidelines for ergonomic design of thumb-operated tools and hand-held electronics devices.