Trapeziometacarpal joint movement during pinching measured by ultrasonography

Functional hand activity induces complex motion of the trapeziometacarpal (TMC) joint. Analyzing the TMC joint motion in vivo can aid in understanding joint behavior and lead to advancements in joint health evaluation. The purpose of this study was to quantify TMC joint motion during pinching using ultrasonography. Healthy participants ( n = 10) held a pinch meter in key pinch configuration and pinched to three prescribed force levels. Ultrasonography was used to record the motion of the TMC joint. The position and rotation of the first metacarpal were calculated. Repeated measures one-way ANOVAs were used for comparisons (α = 0.05). When the pinch force was increased from 0 to 10, 20 and 30 N, the first metacarpal translated in the dorsal(+)/volar(-) direction -0.3 mm [95 % CI: (-0.5 mm, -0.1 mm); p = 0.0151], -0.5 mm [95 % CI: (-0.8 mm, -0.1 mm); p = 0.0113] and -0.8 mm [95 % CI: (-1.4 mm, -0.2 mm); p = 0.0146]. Significance was not observed for proximal(+)/distal(-) translation ( p = 0.224). The metacarpal rotated in the abduction(+)/adduction(-) direction 0.7° [95 % CI: (-0.8°, 2.1°); p = 0.3239], 2.6° [95 % CI: (0.1°, 5.1°); p = 0.0416] and 3.3° [95 % CI: (0.2°, 6.3°); p = 0.0393], at pinch forces of 10, 20 and 30 N, respectively. The TMC joint undergoes volar translation and abduction rotation during pinch tasks. Ultrasonography can be used to quantify this motion and aid in the advancement of joint behavioral study.