In Vivo Length Changes of the Proximal Interphalangeal Joint Proper and Accessory Collateral Ligaments During Flexion

Abstract

To investigate the length changes in proper collateral ligament (PCL) and accessory collateral ligament (ACL) during flexion of the proximal interphalangeal (PIP) joint invivo and how portions of the PCL and ACL stabilize the PIP joint. We obtained computed tomography scans of the index, middle, and ring fingers of one hand from 6 volunteers at 0°, 30°, 60°, 90°, and full flexion of the PIP joint. Radial and ulnar PCL and ACL were measured and analyzed with computer modeling. The data showed that during flexion the average length of the dorsal portion of the radial and ulnar PCL increased significantly and reached a maximum at 90°. The volar portion of the radial and ulnar PCL and the distal portion of the radial and ulnar ACL shortened continuously from extension to full flexion. The proximal and middle portions of each ACL are nearly isometric, the dorsal portion of each PCL becomes taut only in flexion, and the volar portion of PCL and the distal portion ofACL become taut only in extension. The current findings indicate that the dorsal portion of PCLis the most stabilizing structure during flexion of the PIP joint, and that the volar portion of PCL and the distal portion of ACL provide the crucial lateral stability to the joint at extension. The results may provide information relevant to the ligaments of PIP joint reconstruction and rehabilitation.