In vivo analysis of carpal kinematics and comparative review of the literature.

PURPOSE: Techniques have been developed very recently with which it is possible to quantify accurately in vivo 3-dimensional (3-D) carpal kinematics. The aim of this study was to evaluate the feasibility of our novel 3-D registration technique by comparing our data with data found in the literature. METHOD: The right wrists of 11 healthy volunteers were imaged by spiral computed tomography (CT) during radial-ulnar deviation and 5 of those wrists were imaged also during flexion-extension motion. With a matching technique relative translations and rotations of the carpal bones were traced. We compared our in vivo results with data presented in the literature. RESULTS: We found our in vivo data largely to concur with in vitro data presented in the literature. In vivo studies revealed only larger out-of-plane motions within the proximal carpal row than described in most in vitro studies. In vivo studies also showed larger interindividual variations. CONCLUSIONS: A single functional model of carpal kinematics could not be determined. We expect that in vivo 3-D CT studies on carpal kinematics, especially when applied to dynamic wrist motion, will have future diagnostic applications and provide information on long-term results of surgical interventions.

Scaphoid kinematics in vivo.

The purpose of this study was to quantify 3-dimensional (3-D) in vivo scaphoid kinematics during flexion-extension motion (FEM) and radial-ulnar deviation (RUD) of the hand. The right wrists of 11 healthy volunteers were imaged by spiral computed tomography during RUD and 5 of those wrists also during FEM. With a matching technique, relative translations and rotations of the scaphoids were traced. Our results showed a broad spectrum of kinematic patterns of the scaphoid during RUD, with small intercarpal motions within the proximal carpal row. Some scaphoids rotated basically around the flexion-extension axis only whereas others rotated almost entirely around the deviation axis during RUD. During FEM we found highly uniform scaphoid motion patterns with large intercarpal motions within the proximal carpal row. These findings suggest that current theories cannot sufficiently explain wrist kinematics and stress the need for more in vivo studies on 3-D carpal kinematics.

Impact load on the triangular fibrocartilage of the wrist: a cadaver study.

OBJECTIVE: The aim of this study was to study the role of the triangular fibrocartilage of the wrist in attenuating and transmitting axial force on the ulnar side of the wrist. DESIGN: Ten biopsies from the triangular fibrocartilage of fresh cadaver wrists were subjected to repetitive axial load during 4 h under reproducible conditions. Another five biopsies were subjected to a higher load and for a longer compression time. Finally, five biopsies were compressed at a (three times) higher compression rate. The amount of force transmitted and attenuated as well as the loaded deformation was measured. RESULTS: From the first experiment we concluded that 53% of the axial force was attenuated. More force was attenuated (61%) if the axial load was increased but still kept within the physiological boundaries. However, increasing the compression rate beyond the physiological boundaries showed that only very little force is attenuated (11.2%). CONCLUSION: The triangular fibrocartilage of the wrist has an important force attenuating function and should not be easily resected.