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Dynamic EMG of peroneus longus in hemiplegic children with equinovarus
C Boulay1, M Jacquemier2, V Pomero2
1Laboratoire de la marche, service de chirurgie orthopédique pédiatrique, CHU La Timone-Enfants, 264, rue Saint-Pierre, 13385 Marseille cedex 05, France; Service de neurologie pédiatrique, CHU La Timone-Enfants, 13385 Marseille, France; Institut des sciences du mouvement, Aix-Marseille université, UMR CNRS 6233, 13385 Marseille, France.
Insights
In hemiplegic children with equinovarus, premature electromyography (EMG) activity in the gastrocnemius medialis (GM) and peroneus longus (PL) muscles during the swing phase suggests a motor command dysfunction, not secondary imbalance.
Area of Science:
- Neurology
- Biomechanics
- Pediatrics
Background:
- Equinovarus in hemiplegic children is linked to premature gastrocnemius medialis (GM) electromyography (EMG) activity before initial foot contact.
- Understanding the timing of muscle activation is crucial for addressing gait abnormalities.
Purpose of the Study:
- To investigate the onset of EMG activation in the GM and peroneus longus (PL) muscles during gait in hemiplegic children with equinovarus.
- To determine if PL muscle activity is also prematurely activated, similar to GM.
Main Methods:
- Electromyography (EMG) of the PL and GM muscles was recorded in 15 hemiplegic children with equinovarus during walking.
- EMG data was normalized to the gait cycle percentage, with activation defined by a 20μV threshold.
- A paired t-test compared the activation onset between the PL and GM muscles.
Main Results:
- In healthy limbs, GM and PL muscle activity initiated during the stance phase (ST).
- In hemiplegic limbs with equinovarus, both GM and PL muscles showed premature activation during the swing phase (SW).
- The difference in activation timing between healthy and hemiplegic sides was statistically significant (P<0.001).
Conclusions:
- Premature EMG activity in PL and GM muscles preceding initial contact likely stems from motor command dysfunction, not secondary imbalance.
- The PL muscle's premature activation contributes to the equinus deformity, but its role in varus genesis requires further investigation.
- Future EMG studies should incorporate assessments of PL and tibialis posterior muscle strength, alongside foot bone morphology.
Objective:
In hemiplegic children the appearance of equinovarus is correlated with premature electromyography (EMG) activity of the gastrocnemius medialis (GM) prior to initial contact. The goal was to analyze the onset of EMG activation in the GM and, more particularly, the peroneus longus (PL) in cases of equinovarus: is PL activity likewise premature?
Material And Methods:
As 15 hemiplegic children (age 5 years±1.5) with equinovarus walked, their PL and GM EMG activity was being recorded. The latter was normalized in terms of gait cycle percentage (0-100%) and detected through semi-automatic selection with activation threshold set at 20μV. A paired t-test compared activation onset of the PL versus the GM muscles.
Results:
As regards the healthy limb, activity onset of the GM (+14.55%) and the PL (+19.2%) muscles occurred only during the ST. In cases of equinovarus, activation of the GM (-5.2%) and the PL (-6.1%) occurred during the SW and was premature. For each muscle, comparison between the healthy and the hemiplegic side was highly significant (P<0.001).
Conclusion:
Premature PL and GM EMG activity preceding initial contact corresponds not to a disorder secondary to imbalance but rather, more probably, to motor command dysfunction. While the PL consequently contributes to equinus deformity, its possible role in varus genesis is less evident. EMG study needs to be completed by comparing PL and tibialis posterior strength while taking foot bone morphology into full account.
