A new method for measuring wrist-joint ligament length changes during sagittal and frontal motion

Objective. The present study addresses elongation patterns of selected capsular wrist ligaments during two types of planar wrist motion. Design. In vitro continuous measurement of capsular ligament elongation using miniature cisplacement transducers. Background. The function of the capsular wrist ligaments in carpal kinematics is still to be determined unambiguously. Most previous studies on carpal ligament behaviour were realised using X-ray stereophotogrammetric methods. Methods. Elongation of the palmar radiolunate, radiocapitate and ulnocapitate ligaments, as well as of the dorsal radiotriquetral ligament during frontal and sagittal wrist motion were analysed in 10 anatomical specimens using miniature differential variable reluctance transducers. Wrist motion was tracked using a six-degree-of-freedom electrogoniometer. Results and conclusions. In most instances, the elongation of these ligaments was similar for two motion modalities tested (guided by a rail or free) with, however, a trend to larger individual variations and smaller elongation during free motion for several ligaments. The capsular ligaments considered in this study displayed length changes inferior to 15% of the initial length. The individual elongation patterns and ranges were highly variable, contrasting with excellent intra-individual reproducibility. Relevance This study presents a method for continuous tracking of in vitro ligament elongation patterns liable to provide new features if applied after simulation of wrist disorders. Besides morphologic and kinematic variations shown previously, the wrist seems to display variations in ligament length changes, which could partially explain the variability of carpal bone motion, although further studies are needed to determine the influence of their variations on carpal kinematics.