Abstract
We used ultrasound-derived echo intensity and hand-held dynamometry to characterize plantar flexor muscle contractures in adults with cerebral palsy (CP). Eleven adults with CP (aged 41 ± 12 y, Gross Motor Function Classification System I-II) and 11 neurologically intact adults (aged 35 ± 10 y) participated in the study. Echo intensity was measured from the medial gastrocnemius muscle using brightness mode ultrasound. Hand-held dynamometry was used to quantify plantar flexor passive muscle stiffness and ankle joint passive range of motion (pROM). Echo intensity correlated with both passive muscle stiffness (r=0.57, p=0.006) and pROM (r=-0.56, p=0.006). Ultrasound echo intensity (p=0.02, standardized mean difference [SMD]=1.13) and passive muscle stiffness (p < 0.001, SMD=1.99) were higher and ankle joint pROM (p < 0.001, SMD=2.69) was lower in adults with CP than in neurologically intact adults. We conclude that combined ultrasound-derived echo intensity and hand-held dynamometry may be used to provide an objective characterization of muscle contractures.
Highlights
As a result of rapid increases in the availability and affordability of ultrasound devices, muscle ultrasound is routinely used in the evaluation of individuals with neurological disorders
We found a significant correlation between echo intensity (EI) and both passive muscle stiffness (Fig. 5: r = 0.57; 95% confidence interval [CI]: 0.18, 0.79; p = 0.006) and passive range of motion (pROM) (Fig. 6: r = À0.56; 95% CI: À0.79, À0.17); p = 0.006)
We found that EI is significantly related to established biomechanical measures of muscle contractures and, that EI seems to be related to the intramuscular infiltration of fibrous tissue associated with muscle contractures (Smith et al 2011; Mathewson and Lieber 2015)
Summary
As a result of rapid increases in the availability and affordability of ultrasound devices, muscle ultrasound is routinely used in the evaluation of individuals with neurological disorders. In addition to more established uses (e.g., quantification of muscle size and architecture), ultrasound is being introduced as a tool to quantify general muscle composition (Stock and Thompson 2021). Ultrasound EI is widely used to quantify muscle composition in both neurologically intact (NI) individuals and individuals with neurological disorders, it is relatively unknown to what extent different body tissues affect the EI (Stock and Thompson 2021). In populations in which the accumulation of fibrous tissue is relatively homogenous (e.g., the NI population), it might be reasonable to assume that ultrasound EI is largely explained by the accumulation of intramuscular fat. In populations with larger variability in the accumulation of fibrous tissue, (e.g., the cerebral palsy [CP] population), this might not be the case
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