Tibial nerve excursion during lumbar spine and hip flexion measured with diagnostic ultrasound

Ultrasound imaging provides a method for non-invasive in vivo measurement of nerve motion resulting from joint movement. This study measured the proximal excursion of the tibial branch of the sciatic nerve at the popliteal fossa during forward bending in healthy subjects. Long-axis image sequences of the nerve were analysed using frame-by-frame cross-correlation software that calculated the longitudinal and axial movement of the nerve. Proximal excursion was calculated from the hypotenuse of these values. The mean proximal excursion recorded was 12.2 mm (SD 2.2 mm, n = 24). The reliability of three repeat measurements was found to be excellent (ICC 0.97, 95% CI 0.93-0.99; SEM 0.7 mm, n = 21). The protocol described provides a reliable method for analysing tibial nerve movement that could prove useful in future clinical studies.