Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Habersack, A.
Biomechanical properties of Gastrocnemius muscle and Achilles tendon
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Medizinische Universität Graz; 2024. pp. 99
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Kraus Tanja
- Svehlik Martin
- Altmetrics:
- Abstract:
- Spastic cerebral palsy, which can be divided into unilateral and bilateral subtypes, is a common neurodevelopmental disorder in childhood. However, the majority of studies that have examined the muscle-tendon properties of the lower limb muscles in individuals with spastic cerebral palsy have not distinguished between the two subtypes. One of the most significant factors influencing the functionality of spastic muscles is their morphological characteristics. Therefore, different muscle-tendon pathologies may require different treatment strategies. Accordingly, one aim of this thesis was to conduct a comparative analysis of the muscle and tendon characteristics of children with unilateral or bilateral spastic cerebral palsy. The use of valid and reliable measurement methods is critical in assessing potential differences at the musculotendinous level. Therefore, in a study performed beforehand, a 3D ultrasound approach was developed for the assessment of the gastrocnemius medialis muscle belly, muscle-tendon unit, and Achilles tendon lengths. This approach was evaluated with regard to two key aspects: firstly, its validity in comparison to magnetic resonance imaging, and secondly, its reliability for static and dynamic length measurements. In order to evaluate the reliability and validity of the 3D ultrasound approach, two ultrasound assessment sessions and one magnetic resonance imaging examination were conducted. The tissue lengths were assessed at a fixed ankle joint position by combining 3D motion capture techniques, 2D ultrasound and vector algebra. Subsequently, the aforementioned measurements were then compared to those obtained from magnetic resonance imaging. The intra- and inter-rater reliability of the static and dynamic length assessment was evaluated using various statistical parameters including standard errors of measurement, coefficients of variation, intraclass correlation coefficients, and minimal detectable changes. A total of 33 ambulatory children were included to assess the muscle-tendon properties of the spastic cerebral palsy subtypes. Of these, 15 had unilateral and 18 had bilateral spastic cerebral palsy. Isometric muscle strength, ankle joint range of motion, and muscle-tendon properties of the gastrocnemius medialis muscle-tendon unit (e.g., muscle volume, tissue lengths and lengthening behaviour) were assessed using isokinetic dynamometry, 3D motion capture, and ultrasound, respectively. Independent t-tests or Mann-Whitney-U-tests were used to test for group differences with a level of significance set at α = 0.05. A comparison of the 3D ultrasound approach with magnetic resonance imaging revealed a slight underestimation of tissue lengths, with a difference of approximately 1.1%. Moreover, the approach demonstrated excellent intra- as well as inter-rater reliability, as indicated by high intraclass correlation coefficients (≥ 0.94), small standard errors of measurement (≤ 1.3 mm), and good values for minimal detectable change (≤ 3.6 mm). No significant differences were observed in any of the assessed parameters between children with unilateral or bilateral spastic cerebral palsy (p > 0.05, d < 0.57). The proposed 3D ultrasound approach was found to be reliable and valid for the assessment of the gastrocnemius medialis muscle belly, muscle-tendon unit, and Achilles tendon lengths, as well as the lengthening behaviour of these tissues. It has been demonstrated that the approach can serve as a valuable measurement technique for examining both static and dynamic muscle-tendon characteristics. The functional and morphological properties of the gastrocnemius medialis muscle-tendon unit seem to be similarly developed in children with unilateral or bilateral spastic cerebral palsy. Therefore, the findings do not indicate a need for modification of study designs in the future to differentiate between individuals with unilateral or bilateral spastic cerebral palsy. Furthermore, the results of this study i