Segmental motion of the proximal carpal row: their global effect on the wrist motion.

The contribution of the scapho-lunate and luno-triquetral joints to global wrist motion was studied in 11 fresh-frozen cadaver specimens. The carpus were labeled with metallic markers and the joints were selectively transfixed with wires. The wrist was allowed to follow its natural radial and ulnar deviation during flexion and extension, extension and flexion during radial and ulnar deviation, respectively. The data was collected by means of radiography, goniometric measurement, and computer analysis. The proximal carpal row (the intercalated segment) although anatomically represented as a row, presented through its two intersegmental joints, a definite segmental behavior. Each intersegmental joint of the proximal carpal row influenced global wrist motion in all directions but to a different degree for each plane of motion. The segmental joints within the intercalated segment collectively govern 40% of the wrist flexion, 33% of extension, and 10% of ulnar deviation. The scaphoid through its scapho-lunate link exerts a governing effect on total intersegmental proximal carpal row contribution to the global wrist motion.