Ultrasound Evaluation of Tibial Vasculonervous Structures for Tibial Nerve Neuromodulation: A Cross-Sectional Study

Percutaneous tibial nerve neuromodulation is an effective approach for treating genitourinary and anorectal dysfunctions. However, the variability in electrode and needle placement raises concerns about standardization and safety. This study aimed to determine the anatomical distribution of the tibial vasculonervous structures using ultrasound and to analyze the variability of their distribution on the basis of sex and anthropometric factors. A cross-sectional observational study was conducted at Ramón y Cajal University Hospital (Madrid, Spain) between January 2024 and August 2024. A total of 105 healthy adult participants were examined using high-frequency ultrasound. The tibial nerve, artery, and vein were identified at seven predefined points (2-12 cm proximal to the right medial malleolus). The tibial distance, horizontal tibial distance, nerve depth, cross-sectional area, and structural overlap were analyzed. Significant anatomical variability was found in the position (p < 0.001, h2 = 0.287) and depth (p < 0.001, h2 = 0.794) of the tibial nerve along its course. The tibial nerve was more superficial at 2 cm (0.66 [0.24] cm depth) and progressively deepened cranially. Structural overlap increased between 4 and 6 cm, where the tibial artery and vein frequently overlapped the nerve. Sex and body mass index (BMI) significantly influenced nerve depth and its distance from the tibia, whereas sex, BMI, and age were positively correlated with nerve size. The variability in tibial nerve positioning and its relationship with adjacent structures may affect the effectiveness and safety of neuromodulation techniques. Ultrasound guidance could optimize percutaneous procedures. Transcutaneous neuromodulation may be preferable at 2 cm from the malleolus, where the nerve is more superficial and less frequently overlapped. Further studies are needed to confirm clinical implications. The Clinicaltrials.gov registration number for the study is NCT06196112.