Three-dimensional functional workspace of thumb prehension.

ABSTRACT

BACKGROUND: Clinical assessment of thumb motion is challenging, due to the complex anatomy and motion of the thumb. It is especially difficult to measure hand movement during activity, and to measure the effects of surgery that changes the morphology of the thumb. A three-dimensional model of the hand may enable clinicians to better assess prehension and thumb motion at baseline, and following surgical intervention. METHODS: A kinematic model of the hand was developed to measure thumb and finger position during functional tasks, enabling the calculation of the volume of space in which prehension could occur. This method was validated by application to a mechanical model of the hand, and then applied to ten adult participants, using three-dimensional motion analysis with a marker array developed for the purpose of this study. FINDINGS: This method can be used to accurately measure three-dimensional thumb joint range of motion (RoM) and predicted functional workspace during functional activities. The thumb carpometacarpal joint was predominantly responsible for thumb position during functional tasks. Predicted functional workspace is proportional to hand morphometric measurements. INTERPRETATION: A kinematic model of the hand measures thumb RoM and predicts functional workspace during functional activities.