The In Vivo Study Of Three-dimentional Kinematics Of Carpal Bones

Objective To accurately quantify three-dimentional in vivo kinematics of all carpal bones in wrist flexion and extent ion and radial and ulnar deviation.Methods The right wrists of 10 healthy adult volunteers were imaged by spiral CT at the neutral posture and at 30°, 60° posture during wrist flexion-extension motion and at 10°, 20° posture during wrist ulnar-radial deviation. One regular-dose scan(130mA) was used at the neutral posture and the subsequent scans during wrist motion were performed with one-tenth of the regular dose(15mA). The bones 3D analysis, the centroid and moments of inertia and finite helical axis of distal radius and carpal, the 3D coordinate system and the 3D measurement all can be performed in our computer-operated simulation system. The 3D carpal bones kinematics which is refered to distal radius can be gained. Then comparing our data with data found in the literature. Results The carpal bones of the distal row and the proximal row not only have the flexion-extension and rotation motion but also have the ulnar-radial deviation during wrist ulnar-radial deviation. And at wrist flexion-extension motion, the carpal bones flex and extend and rotation with ulnar-radial deviation. The motion of distal row of carpal bones are similar as a rigid body, but the proximal one are significantly different from each other. The scaphoid motion is the largest,the carpal bones within the proximal row move synergistically. In our studies revealed larger out-of-plane motions within the proximal carpal row than described in most in vitro studies. The lunate contribute less to wrist flexion and contribute more to wrist extension. At 20° ulnar deviation of the wrist, the mean extension of the scaphoid, the lunate, the triquetrum are larger than others. At 20° radial deviation of the wrist,the scaphoid flexes more than others. The degree of intercarpal motionbetween the scaphoid and the lunate shows more during wrist flexion than wrist extension. Our results are most in concordance with previously published in vivo data except some idiographic data. Conclusions All the carpal bones kinematics are three-dimensional direction during wrist flexion-extention motion and ulnar-radial deviation. A single functional mode of carpal kinematics such as the fixed-row and the columns concept could not be determined. The motion of the distal row of carpal bones are similar as a rigid body,the proximal row exhibit more complex patterns that depend on the direction of wrist motion. Most of our results are in concordance with previously published in vitro and in vivo data. The study sufficiently provide some theoretic and technical reference and stress the need for more in vivo studies on 3-D carpal kinematics.