Ultrasound Assessment of the Tibial Nerve at the Retromalleolar Level: Influence of Anthropometric Characteristics and Clinical Implications

<b>Background:</b> Clinical procedures involving the tibial nerve (TN) are complex procedures due to its deep anatomical position and the variability of its course in the retromalleolar region. Few studies have described the ultrasound characteristics of the TN in vivo. This study aims to describe the ultrasound position of the TN and its relationship with the posterior tibial artery (PTA) at the retromalleolar level, evaluating the influence of sex, weight, height, and body mass index (BMI). <b>Methods:</b> A cross-sectional ultrasound study was performed on 100 volunteers. Anthropometric variables were recorded. Ultrasound measurements included the TN perimeter, distance from the medial malleolus to the TN center, depth, and spatial relationship with the PTA. Statistical analyses included Student's <i>t</i>-test, ANOVA, Chi-square test, and Pearson's correlation coefficient, with a significance level of <i>p</i> < 0.05. <b>Results:</b> The mean distance from the TN to the medial malleolus was 2.17 cm, and its mean depth was 0.91 cm. The most common anatomical pattern was Type I (TN posterior to the PTA) (60%). Sex influenced TN position, with men showing greater distances from the medial malleolus to the TN center (2.42 vs. 1.99 cm) and women showing greater depth from the skin surface to the upper edge of the tibial nerve perimeter (0.94 vs. 0.86 cm). Weight (<i>p</i> = 0.004), height (<i>p</i> < 0.001), and ankle circumference (<i>p</i> = 0.006) correlated significantly with TN location, whereas BMI did not (<i>p</i> = 0.253). <b>Conclusion:</b> These findings provide clinically relevant reference data that may improve the precision and safety of different tibial nerve procedures.