Biometrical study of flexion of the long fingers joints in prehension.

The angles of flexion of the three digital joints were measured in 112 hands while grasping test cylinders the diameter of which ranged from 8 to 90 mm. Based on the average of several measurements, the angles of overall and joint-by-joint flexion were determined for each cylinder size. Studied finger by finger, it was shown the each digit has its individual pattern of flexion, the angles of flexion of each joint being different for each finger. Flexion is prevalent in the proximal interphalangeal joint of the index while it is prevalent in the metacarpophalangeal joint of the little finger. When the standard deviation values were calculated, they showed that the individual variations were relatively small in cylindrical grasps. This is the opposite of what was observed in two of the pinches between the thumb and the other fingers. In these cases, the values of the angles of flexion were remarkably dispersed according to the individuals, especially in the proximal interphalangeal joint.