Effects of Forearm Rotational Movements on Median Nerve and Carpal Tunnel Morphology: A Magnetic Resonance Imaging Study

Abstract

Purpose: This study used magnetic resonance imaging (MRI) to investigate the effects of forearm pronation and supination on the morphology of the median nerve and carpal tunnel. Materials and Methods: The MRI images of 177 patients were analyzed. Median nerve cross-sectional area (CSA) and carpal tunnel dimensions (height and width) were measured at four levels in pronation and supination. Statistical analyses evaluated positional differences. Results: Median nerve CSA was significantly smaller, carpal tunnel height decreased, and width increased in supination compared with pronation. Pronation caused dorsoradial displacement of the median nerve, whereas supination led to ulnopalmar displacement and superficial positioning relative to flexor tendons. Conclusions: The median nerve and carpal tunnel undergo morphological changes during forearm pronation and supination, with supination causing positional shifts, reduced CSA, and increased ovality of the carpal tunnel. Clinical relevance: Forearm supination significantly affects carpal tunnel anatomy and morphology, as demonstrated by MRI findings. These findings may serve as a reference for ultrasound-based evaluations and support future efforts to optimize diagnostic and interventional approaches in carpal tunnel syndrome. © 2025 Elsevier B.V., All rights reserved.