Effects of torsions in the wrist joint on carpal-bone behaviour and the radiotriquetral ligaments: an experimental study

The orientations of the radiotriquetral ligaments in the wrist joint suggest the role of counteracting torsions in the radiocarpal joint. This is tested in a series of kinematic experiments with three specimens, the joints being forced to rotate about the longitudinal axis of the third metacarpal. The reorientations of the marked insertion sites of the dorsal and palmar radiotriquetral ligaments are assessed and related to the individual carpal-bone movements. The three specimens react similarly to the imposed torsions: a hyperpronation is related to a dorsal flexion and a hypersupination to a palmar flexion. The dorsal radiotriquetral ligaments are highly addressed during hypersupination, but the palmar ligaments show no significant elongations during hyperpronations. The mechanism of wrist joint injuries due to trauma like a fall on the outstretched hand is poorly documented. The torsions occurring during these trauma are simulated in cadaver experiments. Large effects upon the dorsal ligaments are found in comparison to the palmar ligaments. This indicates that the palmar radiotriquetral ligaments protect the joint against hyperpronations. Planning of the restoration of hand function in the injured hand should include the different roles of these two ligaments.