Biomechanical Analysis of the Stress Force on Midcarpal Joint in Kienböck's Disease

Abstract

Two types of lunate were recognized in the midcarpal joint. Type I lunate has no facet articulation with the hamate, and Type II lunate has a facet articulation with the hamate. The purposes of this study are to estimate the biomechanical contribution of Type II lunate for Kienböck's disease, and to elucidate the change of the contact surface between the lunate and hamate during radial and ulnar deviation for both Type I and Type II. Twenty-four contralateral unaffected wrists with Kienböck's disease were used for the first purpose. The radiographic force analysis was performed with a modified two-dimensional rigid-body spring model computer-simulation technique. Six wrists of volunteers (3 of Type I and 3 of Type II lunates) were used for the second purpose. Dynamic examination on lunohamate joint was carried out using magnetic resonance imaging. The force distribution between the radius and Type II lunate was greater than that between the radius and Type I lunate statistically. Furthermore, the impingement of articular cartilages between Type II lunate and hamate was observed in ulnar deviation on dynamic study. These results suggest that Type II lunate was one of the anatomical risk factors for Kienböck's disease.