Ultrasonographic evaluation of needle electromyography insertion into the tibialis posterior using a posterior approach

Objective: To estimate the safety window for needle insertion in the posterior approach to the tibialis posterior by ultrasonography, particularly in a clinical setting. Design: Cross-sectional study. Setting: University hospital. Participants: Healthy volunteers (108 legs, from 22 men and 32 women). Interventions: Not applicable. Main Outcome Measures: Distance between the tibia and neurovascular bundles in the posterior aspect of the tibia on a transverse ultrasonographic scan. Results: The safety window at the midpoint was significantly larger than the upper third (0.622.16cm, average 1.47±0.38cm vs 0.511.62cm, average 1.16±0.31cm). The depth at the midpoint was significantly more shallow than the upper third (1.573.16cm, average 2.31±0.34cm vs 1.763.66cm, average 2.52±0.38cm). Body weight, height, tibial length, and leg circumference showed positive correlation with the safety window at both points. Conclusions: The midpoint may be more favorable than the upper third for needle insertion to the tibialis posterior with a posterior approach.