Ultrasound detection of sciatic nerve movements with ankle dorsiflexion/plantar flexion: Prospective comparative study of a novel method to locate the sciatic nerve.

ABSTRACT

OBJECTIVES: It is possible to observe the in-vivo movements of nerves using real-time ultrasound. In this study, we aimed to visualize the movements of the sciatic nerve as a guide to identify the sciatic nerve to distinguish from surrounding tissue. METHODS: This trial was a prospective, cross-over comparative study. We included 25 healthy volunteers in this study. The movements of the sciatic nerve were visualized in the transverse view at popliteal and midthigh levels using ultrasonography. Anterior-posterior movements were assessed by measuring skin-to-nerve distance. The distances were measured during maximum ankle dorsiflexion, maximum plantar flexion and neutral position and compared with each other. We also evaluated the quality of dynamic (real-time) rotation/lateral movements of the sciatic nerve by assigning a subjective observer score. RESULTS: The movement of sciatic nerve was significant at popliteal region with active and passive ankle dorsiflexion which was 0.32 cm and 0.23 cm respectively (p=0.003). The movement of sciatic nerve was significant at midthigh region with active and passive ankle plantar flexion which was 0.11 cm and 0.01 cm respectively (p<0.001). Excellent rotation/lateral movement was observed in subjects at popliteal region and good rotation/lateral movement was observed at midthigh level. CONCLUSION: Sciatic nerve movement can be observed with ankle dorsiflexion and plantar flexion in the transverse plane at popliteal and midthigh locations under real time ultrasound. This preliminary study suggest that observing the movements of sciatic nerve is potentially valuable in clinical sciatic nerve blocks for facilitating the localization of the sciatic nerve.