Anatomy of the oblique retinacular ligament of the index finger.

The available literature includes conflicting descriptions of the anatomy and function of the oblique retinacular ligament. We have studied this ligament in the index finger to better define its presence, configuration, points of attachment, length, and relationship to the proximal interphalangeal joint axis. Twenty fresh frozen index fingers were dissected. Five additional specimens were decalcified, mounted, sectioned transversely at 1 mm intervals and studied under the microscope. An oblique retinacular ligament was identified on the radial side of the index finger in 95% and on the ulnar side in 90% of the specimens. The radial oblique retinacular ligament was usually longer and more developed than the ulnar oblique retinacular ligament. Proximally, the ligament arose from the middle third of the proximal phalanx and the A-2 pulley whereas, distally, it inserted into the lateral extensor band with a fan-shaped expansion centered 4 to 6 mm distal to the proximal interphalangeal joint line. In 70% of the specimens, the oblique retinacular ligament was supplemented by a contribution from the proximal cruciform pulley (C-1). Histologic cross sections also confirmed the presence of the oblique retinacular ligament but not the supplemental contribution arising from the C-1 pulley. The relationship of the oblique retinacular ligament to the proximal interphalangeal joint axis is dependent on the proximal interphalangeal joint position; the ligament lies palmar to the proximal interphalangeal joint axis only when the proximal interphalangeal joint is flexed.