An anatomical study of the palmar ligamentous structures of the carpal canal.

To determine which structures should be divided for complete release of the carpal canal, we studied the palmar structures in 12 embalmed and eight fresh cadaveric hands. In all hands, fibres run transversely between the thenar and hypothenar fascia, distal to the flexor retinaculum in a layer separate from it. In fresh cadaveric hands, we first released only the flexor retinaculum as in endoscopic management of carpal tunnel syndrome and then these distal fibres. When the flexor retinaculum was released, the mean distance between the sectioned ends of the flexor retinaculum was 1.3 mm. When the distal fibres were also divided, the mean distance was 6.6 mm. We conclude that release of both the flexor retinaculum and the distal transversely running fibres is essential for complete release of the carpal canal in endoscopic surgery.