Morphometric and topographic analysis of the flexor carpi radialis tendon, its tunnel, and the median nerve: an MRI-based anatomical guide for wrist interventions.

PURPOSE: This study aimed to evaluate the morphometric features of the flexor carpi radialis(FCR) tendon and its tunnel, and their topographical relationships, using wrist magnetic resonance(MR) images. METHODS: Axial MR images of 190 individuals aged 18–45 years (95 women and 95 men) were retrospectively analysed. Measurements included distances of the FCR tendon to the radial artery (RA), ulnar artery (UA), median nerve (MN), and scaphoid; trapezium tubercle dimensions; FCR tunnel angle, area, and retinacular thicknesses; retinaculum bending ratio; FCR tendon–to–MN area ratio; and FCR tunnel–to–carpal tunnel ratios. The topographic relationship between the FCR tendon and MN was assessed at the levels of the FCR tunnel and pisiform. Positions of the MN and other tendons in the carpal tunnel were also recorded. RESULTS: The mean FCR tunnel area was 8990 ± 2238 mm2 in males and 7979 ± 1792 mm2 in females. Significant sex-related differences were identified in the distances of the FCR to the RA, UA, and MN, as well as in tunnel areas (p < 0.05). Right–left comparisons revealed significant differences in the distances of the FCR to the scaphoid, UA, and MN, in the FCR tunnel area, and in retinacular thickness above and below the tunnel (p < 0.05). Variations were observed in the structures between the FCR tendon and MN, and in MN positioning relative to other tendons. CONCLUSION: The findings may provide an anatomical guide to how FCR-region variations influence invasive procedures, particularly in conditions such as carpal tunnel syndrome and FCR tendinopathy, considering sex and laterality.