This study aimed to explore the use of a contemporary motion capture system for measuring in vivo maximum thumb circumduction, and through biomechanical modeling and statistical analysis, to establish a normative database of three-dimensional functional thumb range of motion (ROM) and examine the effects of anthropometry and gender. Twenty-eight (14 males and 14 females) anthropometrically diversified subjects performed maximum voluntary thumb circumductions, as the trajectories of surface markers placed on their thumb landmarks were measured by an opto-electronic motion capture system. Aglobographic representation method determined the best fitting spheres, the center of rotation (COR) expressed in a local coordinate system, and reference axes of thumb circumduction. Thumb ROM was quantified using (1) the cone volume circumscribed by the thumb, and (2) the time-varying included angle with respect to a reference axis, expressed as the joint sinus. Statistical analyses suggest that gender is the most important factor ( p < 0.05) in determining the COR while anthropometry has the most significant effect on the cone volume ( p < 0.0001), but neither affects the joint sinus measures. The results provide valuable data as well as insights for biomechanical modeling of hand movement, ergonomic design of hand-operated controls or devices, and evaluation of thumb impairments or disorders.
Modeling and evaluating beat gestures for social robots
