Related Experiment Videos
Determinants of muscle function in the spastic lower extremity
1Rancho Los Amigos Medical Center, Downey, CA 90242.
Clinical Orthopaedics and Related Research
|March 1, 1993
Summary
Upper motor neuron lesions in hemiplegia reveal primitive muscle activation patterns affecting gait. Dynamic electromyography identified these mechanisms, crucial for understanding gait inconsistencies in patients.
Area of Science:
- Neuroscience
- Biomechanics
- Clinical Medicine
Background:
- Upper motor neuron lesions causing hemiplegia disrupt selective motor control.
- This disruption leads to the emergence of primitive muscle activation patterns.
- A discrepancy often exists between clinical assessments and observed patient gait.
Purpose of the Study:
- To investigate the primitive neuromuscular mechanisms underlying gait inconsistencies in hemiplegia.
- To evaluate the reliability of clinical tests in differentiating spasticity and contracture.
- To understand how changes in body position affect muscle tone and spasticity.
Main Methods:
- Dynamic electromyography (EMG) was employed to analyze muscle activation during gait.
- Stretch reflexes were assessed using varying rates of stretch (quick vs. slow).
- Muscle responses were evaluated across different body positions (supine, sitting, standing) and during specific movements like knee flexion.
Main Results:
- The rate of muscle stretch did not reliably differentiate spasticity from contracture.
- Knee flexion proved unreliable for distinguishing gastrocnemius and soleus spasticity.
- Increased spasticity was observed with changes in body position, particularly from supine to sitting and standing.
- Primitive mass extension and flexion synergies, along with simultaneous muscle activation patterns, interfere with normal walking progression.
- Specific synergies were identified, such as premature ankle plantar flexion during stance and inhibited knee extension during swing phase.
Conclusions:
- Dynamic EMG is essential for understanding gait deviations in hemiplegia.
- Clinical assessments for spasticity and contracture require careful interpretation due to unreliable responses to stretch and position changes.
- Primitive synergistic patterns significantly impact gait mechanics, leading to functional limitations.
- Gait analysis, whether observational or instrumented, is critical for effective surgical planning in hemiparetic limb treatment.