title: Measurement of tibial nerve excursion during ankle joint dorsiflexion in a weight-bearing position with ultrasound imaging.
abstract: BACKGROUND
  The ability of peripheral nerves to stretch and slide is thought to be of paramount importance to maintain ideal neural function. Excursion in peripheral nerves such as the tibial can be measured by analysis of ultrasound images. The aim of this study was to assess the degree of longitudinal tibial nerve excursion as the ankle moved from plantar flexion to dorsiflexion in a standardised weight-bearing position. The reliability of ultrasound imaging to measure tibial nerve excursion was also quantified.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: School of Rehabilitation & Occupation Studies, Health & Rehabilitation Research Institute, Department of Podiatry, AUT University, Private Bag 92006, Auckland 1142, New Zealand. matthew.carroll@aut.ac.nz.
authors.forename: Matthew
authors.initials: M
authors.lastname: Carroll
authors.forename: Janet
authors.initials: J
authors.lastname: Yau
authors.forename: Keith
authors.initials: K
authors.lastname: Rome
authors.forename: Wayne
authors.initials: W
authors.lastname: Hing