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Medial Gastrocnemius Muscle Architecture in Children with Idiopathic Toe Walking and the Effect of Serial Casting

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Date

2023

Authors

Supervisor

McNair, Peter
Wilson, Nichola

Item type

Thesis

Degree name

Master of Philosophy

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Auckland University of Technology

Abstract

Background Idiopathic toe walking (ITW) is persistent toe walking after the age of two years, following the exclusion of any neurological or orthopaedic abnormalities or neuropsychiatric diagnoses. It is not currently known whether the triceps-surae muscle structure of children with ITW is different to that of typically developing children (TDC). Current treatment is aimed at maintaining or increasing ankle dorsiflexion (DF) range and retraining the walking pattern. A period of serial casting is commonly used to achieve this goal. There is little evidence on the effect the casting has on triceps-surae muscle structure and how this relates to any change in ankle DF range of motion (ROM), achieved with serial casting. Objective The objective was firstly to examine differences in ankle ROM and medial gastrocnemius muscle architecture between children with a diagnosis of ITW and TDC. Secondly, to investigate changes in medial gastrocnemius muscle architecture and ankle ROM following serial casting for the treatment of ITW, and finally to assess the relationship between changes that occurred in these elements. Study Design A two group, pre- and post-intervention study, with comparisons within and across limbs of ITW and TDC groups was undertaken. Sixteen participants with a diagnosis of ITW underwent assessment pre and one-week post a six-week intervention of serial casting. Seventeen age and gender matched TDC control participants underwent the same assessment protocol on two occasions, seven weeks apart. Method Resting ankle position and maximal ankle DF ROM were measured by goniometry at each assessment point. Medial gastrocnemius muscle-tendon length, tendon length, fascicle length, pennation angle, and muscle thickness were measured with 2D B-mode ultrasound at three joint angles (40° plantarflexion or resting, neutral, maximal DF), at each assessment point. MATLAB and ImageJ software were utilised for post-scanning analysis. Statistical analysis involved a two-factor ANOVA and Pearson correlation coefficients (alpha level 0.05). Results Prior to casting, ankle ROM was significantly decreased (p < 0.05) at rest (mean 13.1° difference, Cohen’s d = -2.4) and at maximal DF (mean 14.7° difference, Cohen’s d = -3.3) in the ITW group, compared to the control group. Between group differences in medial gastrocnemius muscle-tendon length, fascicle length and pennation angle were not clinically significant. The muscle belly to tendon ratio was not significantly different between groups. Muscle thickness was significantly increased (p < 0.05) in the ITW group compared to the control group at all joint angles (mean difference: 0.13cm at 40° plantarflexion, 0.21cm at neutral, 0.18cm at maximal DF). Following serial casting in the ITW group, ankle ROM significantly increased (p < 0.05, mean difference 13.9° at rest, 14.6° at maximal DF). Increases in muscle-tendon length were not clinically significant. Muscle thickness significantly decreased (p < 0.05, mean difference: 0.10cm at 40° plantarflexion, 0.19cm at neutral, 0.12cm at maximal DF). There was no significant difference in ankle ROM or muscle architecture variables between ITW and TDC at follow-up. There was no significant correlation between changes in ankle ROM and changes in medial gastrocnemius muscle architecture in the ITW group following serial casting. Conclusion The findings of this study demonstrate that although children with ITW have significantly decreased ankle DF ROM, overall, their medial gastrocnemius muscle architecture is not wholly different to that of TDC. The exception to this was a finding of increased muscle thickness, which is suggestive of a change in triceps-surae function, with the plantarflexor muscles being active for a greater portion of the gait cycle with toe-walking. The findings following serial casting are reassuring for clinicians who are utilising this treatment modality for ITW, as they suggest that muscle architecture and ankle ROM are improved to a normal range. The lack of correlation between ROM and muscle architecture changes may reflect the relatively small changes which occurred in muscle architecture and the contribution of other tissues to ROM.

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http://hdl.handle.net/10292/16801

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