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Muscle hypoextensibility in children with cerebral palsy: I. Clinical and experimental observations
Insights
Children with cerebral palsy (CP) exhibit reduced triceps surae muscle extensibility, indicating altered muscle properties. This hypoextensibility affects passive muscle stretch and force generation during movement.
Area of Science:
- Biomechanics
- Pediatric Orthopedics
- Neuromuscular Disorders
Background:
- Cerebral palsy (CP) is often associated with altered muscle properties.
- Hypoextensibility in noncontracting muscle suggests changes in physical muscle characteristics.
Purpose of the Study:
- To compare triceps surae muscle extensibility between normal children and those with cerebral palsy.
- To investigate the relationship between muscle hypoextensibility and physical properties in children with CP.
Main Methods:
- Instrumental measurement of torque-angle curves for noncontracting triceps surae muscle.
- Comparison of specific angles related to slight and standardized torque between groups.
- Clinical assessment of muscle and tendon length in relation to force generation.
Main Results:
- Children with CP and muscle hypoextensibility showed abnormally high angles at slight and standardized torque.
- The difference between these angles was significantly smaller in children with CP, indicating reduced passive muscle stretch range.
- Some children with CP demonstrated impaired force generation in full plantar flexion due to shortened muscle and elongated tendon.
Conclusions:
- Muscle hypoextensibility in children with CP is characterized by an insufficient range of passive muscle stretch.
- Abnormal torque-angle curve steepness reflects altered muscle-tendon unit properties.
- Clinical techniques can accurately assess these biomechanical changes, aiding in diagnosis and management.
Abstract:
Extensibility of the triceps surae was compared in 12 normal children and in 21 children with cerebral palsy (CP). The latter group represented selected subjects who showed hypoextensibility in ischemia-tested noncontracting muscle, which is considered an indication of change in the physical properties of muscle. The difference between the 2 groups is illustrated by curves plotting torque of the noncontracting muscle against tibiocalcanean angles. Two measurements were found to be especially representative: 1) the angle related to a very slight torque and 2) the angle corresponding to a strong, standardized torque. In children with CP and with muscle hypoextensibility, both angles had abnormally high values and the difference between the 2 measurements was abnormally small. These findings indicate an insufficient range of passive muscle stretch, reflected by excessive steepness of the torque-angle curve. In normal children, maximal muscle contraction produces full plantar flexion; in some children with CP, contraction fails to produce any force in full plantar flexion. Instead, force is generated only at a smaller tibiocalcanean angle when the muscle reaches a sufficient length. These cases represent hypoextensibility with abnormally short muscle and abnormally long tendon. Data obtained by instrumental measurements can be reproduced with sufficient accuracy by appropriate clinical technique as described in this paper, and applied clinically, as described subsequently.