Sciatic nerve excursion during a modified passive straight leg raise test in asymptomatic participants and participants with spinally referred leg pain

Background: Minimal data exists on in-vivo sciatic nerve motion during straight leg raise (SLR), particularly in symptomatic participants. Such data could help clinicians to better understand nerve mechanic changes following nerve dysfunction. Design: Cross-sectional, controlled laboratory study. Objectives: To investigate whether individuals with spinally referred leg pain have different nerve excursion patterns compared to healthy participants. Method: The sciatic nerve was scanned using ultrasound imaging in the posterior thigh in asymptomatic participants, and individuals with spinally referred leg pain sub-grouped into somatic pain, radicular pain or radiculopathy. Nerve excursion was measured in transverse and longitudinal planes during a side-lying modified SLR. The ultrasound data was analysed off-line using cross correlation software. Longitudinal plane data was collected from 16 asymptomatic and 60 symptomatic participants and transverse plane data from 16 asymptomatic and 56 symptomatic participants. Results: There was no significant difference in longitudinal nerve excursion between the 4 groups. The direction of transverse plane motion altered between groups. These varied movements may be related to protective muscle activation between the groups, although this is speculative at present. Conclusion: Longitudinal sciatic nerve excursion at the posterior thigh during a modified SLR is not different between asymptomatic participants and those with spinally referred leg pain. Transverse plane movement appears to be more varied. This may suggest that in individuals with nerve root pain, there is no restriction in nerve excursion. However, as it was not possible to measure excursion at the nerve root, more research is needed to confirm these findings.