Arthrokinematics of the Distal Radioulnar Joint Measured Using Intercartilage Distance in an In Vitro Model.

Purpose: Current techniques used to measure joint contact rely on invasive procedures and are limited to statically loaded positions. We sought to examine native distal radioulnar joint (DRUJ) contact mechanics using nondestructive imaging methods during simulated active and passive forearm rotation.

Methods: Testing was performed using 8 fresh-frozen cadaveric specimens that were surgically prepared by isolating muscles involved in forearm rotation. A wrist simulator allowed for the evaluation of differences between active and passive forearm rotation. Three-dimensional cartilage surface reconstructions were created using volumetric data acquired from computed tomography. Using optically tracked motion data, the relative position of the cartilage models was rendered and used to measure DRUJ cartilage contact mechanics. The effects of forearm movement method and rotation angle on centroid coordinate data and DRUJ contact area were examined.

Results: The DRUJ contact area was maximal at 10° supination. There was more contact area in supination than pronation for both active and passive forearm rotation. The contact centroid moved volarly with supination, with magnitudes of 10.5 ± 2.6 mm volar for simulated active motion and 8.5 ± 2.6 mm volar for passive motion. Along the proximal-distal axis, the contact centroid moved 5.7 ± 2.4 mm proximal during simulated active motion. These findings were statistically significant. The contact centroid moved 0.2 ± 3.1 mm distal during passive motion (not significant).

Conclusions: It is possible to examine cartilage contact mechanics of the DRUJ nondestructively while undergoing simulated, continuous active and passive forearm rotation. The contact centroid moved volarly and proximally with supination. There were higher contact area values in supination compared with pronation, with a peak value at 10° supination.

Clinical Relevance: This study documented normal DRUJ arthrokinematics using a nondestructive in vitro approach. It further reinforced the established biomechanical and clinical literature on contact patterns at the native DRUJ during forearm rotation.