Kinematic analysis of the scaphoid using gated four-dimensional CT

Abstract

To investigate the kinematics of the scaphoid while the wrist was in radioulnar motion using gated four-dimensional computed tomography (4DCT) imaging. Six cadaveric wrist specimens were scanned in the following order of capsulotomy and ligament sectioning: (1) ligaments intact, (2) capsulotomy, (3) scapholunate ligament division, and lastly, (4) lunotriquetral ligament division. A three-dimensional model was then reconstructed to analyse the translation and angular displacements of the scaphoid. The magnitude of displacement was found to increase with each consecutive ligament sectioning. Translation along the y-axis was statistically significant, with the scaphoid shifting up to 1.39mm from its original position after complete sectioning of the ligaments while the wrist was deviating radially. Angular displacement about all three axes was statistically significant, with the highest occurring in the flexion-extension plane when the scaphoid flexed by 9.1° from its original position after total sectioning of the ligaments. The present study showed that changes in the kinematics of the scaphoid can be detected using 4DCT, thus demonstrating its feasibility in the diagnosis of dynamic carpal instability, which only presents during motion.