Measurement of tibial nerve excursion during ankle joint dorsiflexion in a weight-bearing position with ultrasound imaging

The tibial nerve was imaged over two separate sessions in sixteen asymptomatic participants in a weight-bearing position. Longitudinal nerve excursion was calculated from a three-second video loop captured by ultrasound imaging using frame-by-frame cross-correlation analysis. Intraclass correlation coefficients (ICC) with 95% confidence intervals (CI) were used to assess the intra-rater reliability. Standard error of the measurement (SEM) and smallest real difference (SRD) were calculated to assess measurement error.Mean nerve excursion was 2.99 mm SEM ± 0.22 mm. The SRD was 0.84 mm for session 1 and 0.66 mm for session 2. Intra-rater reliability was excellent with an ICC = 0.93.Assessment of real-time ultrasound images of the tibial nerve via frame-by-frame cross-correlation analysis is a reliable non-invasive technique to assess longitudinal nerve excursion. The relationship between foot posture and nerve excursion can be further investigated.During the gait cycle lower extremity motions such as ankle joint dorsiflexion and pronation of the foot will require the tibial nerve to adapt to positional change imposed by joint motions. To accommodate for positional joint change the tibial nerve possesses mechanical properties which enable it to withstand compression, adapt to repetitive force and stretch and slide in relation to the surrounding tissues [1]. The ability of peripheral nerves to stretch and slide is thought to be of paramount importance to maintain ideal neural function [1-3].Peripheral nerve compression may disrupt the ability of the nerve to stretch and slide [4]. Prolonged compression creates a sequelae of intraneural events that may ultimately lead to impaired nerve sliding [4]. Although compression may affect the mechanical functioning of the tibial nerve, no studies have quantified the degree of in-vivo longitudinal tibial nerve excursion that can be considered normal in a non-pathological state. In-vitro methodologies have demonstrated that 5% - 10%