Anthropometric and clinical analysis of the distal ulna and extensor carpi ulnaris tendon using MRI

To investigate the ulnar groove (UG), extensor carpi ulnaris (ECU) tendon, and ulnar styloid process (USP) parameters in asymptomatic individuals without ulnar-sided wrist abnormalities, to determine whether these values can be anthropometric markers of age and gender and identify their correlations for use in clinical decision-making.

The MRI T1W axial, T2W sagittal, coronal PW and DESS sequences were evaluated in 100 cases (62 women). The UG width, depth and groove opening angle (GOA), ECU tendon width and thickness, and USP base width and length were measured.

For gender, the cut-off, sensitivity, specificity and accuracy values were 8.58 mm, 67, 68 and 66%, respectively, for UG width; 5.3 mm, 53, 68 and 62%, respectively, for ECU width; and 6.4 mm, 55, 74, and 67%, respectively, for USP length. There was no difference concerning age. The tendon width was 63% of the UG width and depth was approximately 51% out of the UG. UG depth was correlated with GOA and tendon thickness (p < 0.001 and 0.03, respectively); UG width with GOA, tendon thickness, and USP base width and length (p = 0.005, 0.01, 0.016, and 0.02, respectively); tendon width-thickness with USP base width and length (p = 0.05); and US base width with US length (p < 0.001).

The gender differences in distal ulnar measurements can be beneficial for surgery and forensic science. UG is wider than ECU tendon, and this is the cause of normal subluxation. Therefore, rather than deepening UG, surgeons should focus on tendon sheath abnormalities as a physiological solution.