A Cadaveric Study of the Carpal Tunnel and Anatomical Variations of the Median Nerve in Vietnamese Adults: Implications for Single Portal Endoscopic Carpal Tunnel Release

INTRODUCTION: Single-portal endoscopic carpal tunnel release using modified Agee technique is widely used in Vietnam. Yet information on the anatomy of the target space of Vietnamese people regarding this technique is scarce. We aimed to characterise the anatomical landmarks and variations of the carpal tunnel to propose a safer surgery. MATERIALS AND METHODS: All twenty hands of ten fresh frozen, unembalmed cadavers of Vietnamese adults were included. Dissection was performed after the vertical line, Kaplan’s cardinal line and the distal wrist crease were drawn. The transverse carpal ligament (TCL), ulnar neurovascular bundle and superficial palmar arch were exposed. Measurements were made using Mitutoyo calliper. The variants of the median nerve and in the course of the thenar motor branch were recorded. RESULTS: The median distances from the TCL distal margin to the distal wrist crease and superficial palmar arch were 31.2mm and 12.7mm, respectively. The ulnar neurovascular bundle was located 5.7mm and 4.4mm ulnar to the vertical line at the level of the TCL proximal margin and at the level of the TCL distal margin, respectively. The thenar motor branch of the median nerve was extra-ligamentous in 19 hands and preligamentous in 1 hand. CONCLUSION: If endoscopic portal is made along the distal wrist crease, blade assembly should not be inserted beyond the 35mm mark on its scale. Instruments should be aimed toward the radial border of the patient’s ring finger. Surgeons should be aware of the preligamentous course of the thenar motor branch although this variant type is rare.