Abstract
The carpometacarpal joint (CMC joint) is a joint constituted of distal carpal row and metacarpal base. The second and third CMC joints have complicated joints and can hardly exercise due to the jagged articulation surface. The fourth and fifth CMC joints are slightly motile at the saddle joint. This mobility makes it possible to deepen the concavity of the palm. The metacarpophalangeal joint (MCP joint) is a joint that enables flexion and extension, abduction and inversion and rotation of the proximal phalangeal base on the metacarpal head. In order to understand the contact area of the joint, it is necessary to investigate the relative contact area of the joint with the movement to the object. In this study, we used magnetic resonance imaging (MRI) to investigate the variation in the three-dimensional contact area and contact distribution of the in vivo CMC joint and MCP joint associated with flexion angle in the state of grasping four kinds of sphere. They displayed mean fifth CMC joint of the little finger contact areas of 78.8±18.4, 87.2±3.3, 84.6±6.3 and 80.0±7.8 mm2 in a neutral position, a soft ball grasping position, a tennis ball grasping position, and a ping-pong ball grasping position, respectively. They displayed mean second MCP joint contact areas of 61.6±4.1, 48.9±15.6, 55.8±3.1 and 74.3±3.7 mm2 in a neutral position, a soft ball grasping position, when grasping a tennis ball, and when grasping a ping-pong ball, respectively.
