A Cadaveric Morphometric Study of the Median Nerve and its Thenar Branch: Surgical Implications for Carpal Tunnel Release

Abstract

Introduction: The median nerve's anatomy within the carpal tunnel is notoriously variable. A comprehensive understanding of these variations, particularly of the recurrent thenar branch, is crucial to avoid iatrogenic injury during surgical procedures like carpal tunnel release.

Objectives: This study aimed to document the anatomical variations of the median nerve in the carpal tunnel and hand.

Methods: This descriptive cadaveric study was conducted on 56 embalmed adult hands. Dissections were performed to expose the median nerve from the distal forearm to its terminal branches in the palm. The branching pattern, number, origin, and course of the thenar motor branch were observed, photographed, and classified according to Lanz and Poisel.

Results: Standard anatomy was observed in 44.64% (25/56) of hands. Variations were present in 55.36% (31/56). A single thenar branch was found in 76.79% of hands, while 23.21% had multiple branches. The thenar branch was extra ligamentous (Lanz '0') in 60.47% and subligamentous (Lanz '1A') in 39.53% of hands with a single branch; no transligamentous branches were observed. The branching pattern was bifurcating in 67.86% and trifurcating in 32.14%. A communicating branch to the ulnar nerve was found in 25% of specimens.

Conclusions: Anatomical variations of the median nerve are highly prevalent. The significant occurrence of multiple thenar branches and subligamentous courses poses a substantial risk of iatrogenic injury during carpal tunnel surgery. Preoperative awareness and meticulous surgical technique are imperative for preventing complications.