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Published on: May 1, 2018
Shear modulus of lower limb muscles in school-aged children with mild hypotonia
Miran Goo1, Leanne M Johnston2, Kylie Tucker1
1The University of Queensland, School of Biomedical Sciences, Brisbane, Australia.
Insights
Children with mild hypotonia exhibit lower muscle shear modulus compared to those with cerebral palsy or Duchenne muscular dystrophy. Muscle stiffness increases with longer muscle length in hypotonic children.
Area of Science:
- Biomedical Engineering
- Musculoskeletal Physiology
- Pediatric Rehabilitation
Background:
- Hypotonia in children is associated with altered muscle properties.
- Understanding muscle shear modulus is crucial for assessing muscle function in pediatric populations.
- Previous research has not fully characterized shear modulus in hypotonic children across different muscle lengths.
Purpose of the Study:
- To compare lower limb muscle shear modulus in children with mild hypotonia against typically developing (TD) children and those with other developmental disorders.
- To investigate the relationship between muscle shear modulus and muscle length (Net-Longitudinal Tension Angle - Net-LTA) in hypotonic children.
- To examine correlations between shear modulus and age, sex, and body mass index (BMI) in this cohort.
Main Methods:
- Shear wave elastography was used to measure resting shear modulus in the rectus femoris, biceps femoris (BF), tibialis anterior (TA), and gastrocnemius lateralis (GL) of 19 children with mild hypotonia.
- Muscle shear modulus was assessed at short and long muscle lengths, defined by Net-LTA.
- Data were compared with existing data from TD children and a scoping review of children with developmental disorders.
Main Results:
- Shear modulus was significantly higher at longer muscle lengths compared to shorter lengths across all four measured muscles in hypotonic children (p < 0.01).
- Shear modulus showed correlations with age (BF-short, GL-short) and BMI (BF-short).
- Children with mild hypotonia had lower shear modulus values than children with Duchenne Muscular Dystrophy and Cerebral Palsy, but not TD children.
Conclusions:
- Muscle shear modulus in children with mild hypotonia increases with greater muscle length (higher Net-LTA).
- Mild hypotonia is characterized by lower muscle shear modulus compared to more severe conditions like Cerebral Palsy and Duchenne Muscular Dystrophy.
- These findings contribute to understanding the biomechanical differences in hypotonic pediatric populations.
Abstract:
The objective of this study is to compare shear modulus of lower limb muscles between children with hypotonia versus typical development (TD) or developmental disorders associated with altered tone. Nineteen children with mild hypotonia (mean age 9.4 ± 2.3y, 13 male) completed assessment of resting shear modulus of rectus femoris, biceps femoris (BF), tibialis anterior (TA) and gastrocnemius lateralis (GL) at short and long lengths using shear wave elastography. Data was compared with previous data from TD children and a scoping review for children with developmental disorders. Data were collated according to Net-Longitudinal Tension Angle (Net-LTA), which is the muscle length expressed as the net proximal and distal joint angles. Effects of Net-LTA (e.g., short, neutral, long) were examined according to sex, age and body mass index (BMI). In children with hypotonia, shear modulus was: higher at longer versus shorter lengths for four muscles (p < 0.01); correlated with age for BF-short (r = 0.60, p < 0.03) and GL-short (r = -0.54, p < 0.03), with BMI for BF-short (r = 0.71, p < 0.05); and not different between sexes (p > 0.05). The shear modulus values for lower limb muscles for children with mild hypotonia were lower than those for children with Duchenne Muscular Dystrophy (TA-neutral), or Cerebral Palsy (GL-neutral), but not TD children (all four muscles). In conclusion, shear modulus increases with longer muscle length (i.e. higher Net-LTA) in mildly hypotonic children. Children with mild hypotonia have lower shear modulus than children with cerebral palsy and Duchenne muscular dystrophy.
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