Topographic anatomy of the recurrent branch of the median nerve using bony landmarks: a clinical-surgical study.

Background: The recurrent branch of the median nerve (RBMN) is a critical structure in carpal tunnel surgeries, where inadvertent injury can lead to significant functional impairment. While soft tissue landmarks are commonly used for RBMN localization, they often vary between individuals and are susceptible to intraoperative shifts. This study aims to establish fixed bony landmarks for the reliable localization of the RBMN, potentially reducing the risk of iatrogenic nerve injury.

Materials and methods: This clinical-surgical study included 58 patients (59 hands) undergoing open carpal tunnel release between January 2020 and September 2022. Intraoperative measurements were taken from the origin of the RBMN to three fixed bony landmarks: the apex of the first metacarpal head, the apex of the third metacarpal head, and the tip of the radial styloid process. Distances were recorded using a sterile, millimeter-calibrated ruler by two independent observers. Statistical analysis included inter- and intra-observer reliability assessments.

Results: The mean distance from the RBMN origin to the first metacarpal head was 39.7 ± 5.2 mm, to the third metacarpal head 50.2 ± 4.7 mm, and to the radial styloid process 59.4 ± 4.9 mm. There were no statistically significant differences in these measurements between male and female patients (p > 0.05). The majority of RBMN branches (67%) were extraligamentous, followed by subligamentous (25%) and transligamentous (8%), as classified by the Lanz classification. Postoperative clinical evaluations using the Boston Carpal Tunnel Questionnaire (BCTQ) showed significant improvements in both symptom severity and functional status (p < 0.001).

Conclusions: Fixed bony landmarks provide a reliable and reproducible method for localizing the RBMN during carpal tunnel release, potentially reducing the risk of nerve injury. These findings support the use of bony reference points as consistent intraoperative guides for safer surgical outcomes.