2013 年 8 巻 3 号 p. 278-292
The objective of this study was to simulate the movements of the bones involved in human forearm rotation. We developed a biomechanical arm model comprising bone, muscle, and ligament components. Computed tomography (CT) scans of a human arm were used to determine the morphology of the humerus, ulna, radius, and hand bones. Magnetic resonance (MR) images were used to create muscle spring models simulating the pronator teres, pronator quadratus, and supinator muscles. Twenty-seven ligaments connecting the bone components were approximated by wire models. We also created several ligament rupture models by eliminating some of the 27 ligaments. Ligaments were removed according to the following four stages: Stage a-I, only dorsal triangular fibrocartilage complex (TFCC); Stage b-I, only palmar TFCC; Stage II, both dorsal and palmar TFCC; Stage III, both dorsal and palmar TFCC plus distal interosseous membrane. In the complete 27-ligament model and in the ligament rupture models, the forearm was rotated to 90° supination and 85° pronation for comparison. In supination, the rupture of the palmar TFCC (Stage b-I) caused a larger difference between the two types of models than the rupture of the dorsal TFCC (Stage a-I). The distal radioulnar joint instability and radial laxity occurred for Stage III rather than Stage II. The distal radioulnar joint was more stable and radial laxity was less pronounced during pronation in the presence of the pronator quadratus muscle than during supination in the absence of this muscle. These findings were in good accord with previous study results.