Intra-assessor reliability and measurement error of ultrasound measures for foot muscle morphology in older adults using a tablet-based ultrasound machine

Lydia Willemse,Benedicte Vanwanseele,Martijn F Pisters,Eveline J M Wouters

doi:10.1186/s13047-022-00510-1

Abstract

BackgroundTo gain insight into the role of plantar intrinsic foot muscles in fall-related gait parameters in older adults, it is fundamental to assess foot muscles separately. Ultrasonography is considered a promising instrument to quantify the strength capacity of individual muscles by assessing their morphology. The main goal of this study was to investigate the intra-assessor reliability and measurement error for ultrasound measures for the morphology of selected foot muscles and the plantar fascia in older adults using a tablet-based device. The secondary aim was to compare the measurement error between older and younger adults and between two different ultrasound machines.MethodsUltrasound images of selected foot muscles and the plantar fascia were collected in younger and older adults by a single operator, intensively trained in scanning the foot muscles, on two occasions, 1–8 days apart, using a tablet-based and a mainframe system. The intra-assessor reliability and standard error of measurement for the cross-sectional area and/or thickness were assessed by analysis of variance. The error variance was statistically compared across age groups and machines.ResultsEighteen physically active older adults (mean age 73.8 (SD: 4.9) years) and ten younger adults (mean age 21.9 (SD: 1.8) years) participated in the study. In older adults, the standard error of measurement ranged from 2.8 to 11.9%. The ICC ranged from 0.57 to 0.97, but was excellent in most cases. The error variance for six morphology measures was statistically smaller in younger adults, but was small in older adults as well. When different error variances were observed across machines, overall, the tablet-based device showed superior repeatability.ConclusionsThis intra-assessor reliability study showed that a tablet-based ultrasound machine can be reliably used to assess the morphology of selected foot muscles in older adults, with the exception of plantar fascia thickness. Although the measurement errors were sometimes smaller in younger adults, they seem adequate in older adults to detect group mean hypertrophy as a response to training. A tablet-based ultrasound device seems to be a reliable alternative to a mainframe system. This advocates its use when foot muscle morphology in older adults is of interest.

Highlights

To gain insight into the role of plantar intrinsic foot muscles in fall-related gait parameters in older adults, it is fundamental to assess foot muscles separately
Eighteen older adults with a mean age of 73.8 (SD: 4.9) years, and ten younger adults with a mean age of 21.9 (SD: 1.8) years participated in the study
The learning curves (Additional file 2), revealed that the standard error of measurement (SEM) of the second set of older adults (n = 6) was less than half the SEM of the first set of older adults (n = 6) for the cross-sectional area (CSA) of FDB, thickness of quadratus plantae muscle (QP), abductor digiti minimi muscle (AbDM), PFprox, PFdist, and FHLlong, whereas the SEM was stable between the second and the third set of participants. For these morphology measures, the data of the first set of older adults was omitted from the reliability analysis

Summary

Introduction

To gain insight into the role of plantar intrinsic foot muscles in fall-related gait parameters in older adults, it is fundamental to assess foot muscles separately. Concurrent with the PIFMs’ related mobility decline, a decreased capacity of the PIFMs to produce force has been observed in older adults [10] In this population, toe flexor weakness is associated with a higher probability of falling [11]. It is important to distinguish the PIFMs as a separate group of foot muscles, as well as to distinguish individual PIFMs, in order to gain more insight in the unique role of PIFMs in fall-related mobility parameters. These insights may lead to the enhancement of related treatment

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