The reliability of measuring medial gastrocnemius muscle-tendon unit lengths during gait.

Francesco Cenni,Lynn Bar-On,Kaat Desloovere,Simon-Henri Schless,Heleen Adams

doi:10.1016/j.gaitpost.2021.09.198

Abstract

Ultrasound imaging combined with 3D motion analysis allows for in-vivo assessment of muscle-tendon unit lengths during gait. The clinical relevance of analysing the medial gastrocnemius (MG) and Achilles muscle-tendon junction (MTJ), MG mid-muscle belly fascicles (FAS) and muscle thickness was shown. However, their reliability error estimations over the gait cycle is unknown. What are the intra- and inter-session errors associated with extracting MG belly, thickness, FAS and tendon lengths using ultrasound during gait in healthy participants? 3D gait analysis was carried out in ten healthy adults as they walked on an instrumented treadmill at a comfortable walking speed. An ultrasound probe was secured on the leg and tracked by 3D motion analysis. Images were collected during two walking trials with the probe on the MG muscle-belly to estimate FAS lengths and muscle thickness, and during two trials with the probe on the MTJ to estimate muscle-belly and tendon lengths. A second session was performed after 5 ± 4 days where a different operator placed the ultrasound probe. The standard deviation (SD) of absolute and relative lengths changes during the gait cycle over different trials were calculated per participant. SD values averaged over participants represented intra- and inter-session errors. For all assessed variables, the intra-session errors were <2.2 mm, except for the FAS lengths (3.1 mm). The inter-session errors were larger than the intra-session, with the highest values found for the absolute muscle-tendon unit lengths (5.6 mm). Relative length errors were smaller than absolute length errors. Intra-session errors, which may reflect natural variability and data processing errors, seem more critical when extracting absolute FAS than muscle-tendon lengths. Standardized probe positioning on the MTJ between sessions may improve the inter-session reliability. Expressing the lengths relative to their lengths as the beginning of the gait cycle reduces the inter-session errors.

Highlights

Conventional clinical 3D gait analysis (3DGA) can be enhanced by the addition of muscle-specific outcomes [1]
The intra- and inter-session kinematic errors (Table 1) were similar to those already reported [14], albeit in the present study a probe was attached to the leg and the participants were walking on a treadmill [15]
Assuming that the natural gait cycle variability and integration with 3DGA are comparable between these muscle features, this highlights higher processing variability for medial gastrocnemius (MG)-FAS than MG-muscle-tendon junction (MTJ) US images, despite experienced operators performing a manual process to limit errors

Summary

Introduction

Conventional clinical 3D gait analysis (3DGA) can be enhanced by the addition of muscle-specific outcomes [1]. Studies have already shown the clinical relevance of adding US imaging to 3DGA, measuring muscle-belly, fascicle (FAS) and tendon length changes during gait in children with cerebral palsy [4,5]. The clinical relevance of analysing the medial gastrocnemius (MG) and Achil les muscle-tendon junction (MTJ), MG mid-muscle belly fascicles (FAS) and muscle thickness was shown. Their reliability error estimations over the gait cycle is unknown. Research question: What are the intra- and inter-session errors associated with extracting MG belly, thickness, FAS and tendon lengths using ultrasound during gait in healthy participants? Expressing the lengths relative to their lengths as the beginning of the gait cycle reduces the inter-session errors

Methods

Results

Conclusion