In vivo analysis of trapeziometacarpal joint arthrokinematics during multi-directional thumb motions

• To evaluate the arthrokinematics of the TMC joint during thumb postures in vivo
• TMC abduction-adduction caused greater joint gliding in RU direction
• TMC flexion-extension caused greater joint gliding in the DV and DP directions

BackgroundThe investigation of the joint arthrokinematics of the trapeziometacarpal joint is critical to comprehend the causative mechanism underlying this common form of osteoarthritis. Therefore, the purpose of this study is to evaluate the arthrokinematics of the trapeziometacarpal joint during thumb postures in vivo.MethodsFifteen healthy participants were enrolled in this study. Static computed tomography images of the 1st metacarpal bone and trapezium were taken at specific thumb postures during thumb flexion–extension, abduction–adduction, and circumduction motions. Images were analyzed to examine the joint gliding, expressed as displacement of the centroid of the articular surface of the 1st metacarpal bone, relative to the trapezium. The gliding ratio, defined as joint gliding in each direction normalized to the dimension of the trapezium joint surface in the given direction, was computed and compared between different thumb motions.FindingsThe results indicate that thumb motions influenced joint gliding. The centroids of the articular surface of the 1st metacarpal bone were primarily located at the central and dorsal–radial regions while executing these motions. The maximum joint gliding of the 1st metacarpal bone occurred in the radial–ulnar direction when performing abduction–adduction, and in the dorsal–volar direction while performing flexion–extension and circumduction, with the gliding ratio values of 42.35%, 51.65%, and 51.85%, respectively.InterpretationActivities that involved abduction–adduction in the trapeziometacarpal joint caused greater joint gliding in the ulnar–radial direction, while flexion–extension resulted in greater joint gliding in the dorsal–volar and distal–proximal directions. Understanding normal joint kinematics in vivo may provide insights into the possible mechanism leading to osteoarthritis of the trapeziometacarpal joint, and help to improve the design of implants.