Accessory Movement of the Lunate during Active Flexion and Extension Motion of the Wrist

Abstract

Abstract. This study investigated the accessory movement of the lunate in the volar-dorsal direction during active flexion-extension motion of the wrist. The right wrist of a healthy 50-year-old (right-handed) male was studied using an ultrasound diagnostic instrument to measure the wrist's continuous motion from (neutral to) flexion to extension (back to neutral). An ultrasound system was applied on the dorsal aspect of the subject's wrist over the radiocarpal joint. The distance between the dorsal plane of the radius and that of the lunate was measured in each image. The distance data were depicted on a graph using the method of least squares. The lunate moved 0.5 mm dorsally during flexion, and it moved 1.5 mm in the palmar direction during extension. The variance value of the 5th degree polynomial expression of the curve was 0.147. It is hoped that our polynomial expression in this study will serve as a frame of reference in the evaluation of a given mode of physical therapy prescribed for subjects with joint dysfunction.