Transverse stability of the carpus. An analytical study.

The stabilizing structures of the transverse carpal arch were studied utilizing an analytical model based on a rigid body spring model theory. This method was used to calculate the relative motion between carpal bones, the distribution of compressive forces in the intercarpal joints, and the tensions in the ligaments under simulated dorsopalmar compression. The contribution of each ligament against the effect of compression was determined by removing ligaments from the model. A multivariate analysis of variance disclosed that sectioning the flexor retinaculum alone does not significantly modify the distribution of forces in ligaments and joints (p = 0.33), and decreases dorsopalmar carpal stiffness by only 7.8%. In contrast, isolated removal of the palmar hamate-capitate ligament causes a pronounced weakening of the carpal structure, from an average of 232 to 131 N/mm (p less than 0.01). If the flexor retinaculum is removed in addition to releasing one palmar intercarpal ligament, a gross instability of the carpal arch is created.