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Step-length asymmetry drivers in unilateral cerebral palsy: Exploring the interplay between neuromotor constraints
Ragab K Elnaggar1, Mahmoud S Elfakharany2
1Department of Health and Rehabilitation Sciences, College of Applied Medical Sciences, Prince Sattam Bin Abdulaziz University, Al-Kharj, Saudi Arabia.
Insights
Step-length asymmetry in children with unilateral cerebral palsy (CP) is driven by neuromotor issues and energy efficiency. Integrated rehabilitation targeting strength, spasticity, and gait efficiency is crucial for improving symmetry.
Area of Science:
- Neurology
- Biomechanical Engineering
- Pediatric Rehabilitation
Background:
- Step-length asymmetry is a common gait deviation in children with unilateral cerebral palsy (CP), impacting energy efficiency.
- The combined influence of neuromotor impairments and energy efficiency on this asymmetry is not well understood.
Purpose of the Study:
- To determine the independent and combined predictive power of neuromotor and energy efficiency factors on step-length asymmetry in children with unilateral CP.
Main Methods:
- Fifty-two children (8-18 years, GMFCS I-II) with unilateral CP were assessed.
- Neuromotor function (dorsiflexor strength, spasticity, range of motion, proprioception) and energetic efficiency (metabolic cost, walking speed) were measured.
- Step-length asymmetry was calculated as the percentage difference between limbs.
Main Results:
- A comprehensive model explained 70% of the variance in step-length asymmetry.
- Neuromotor impairments were the primary predictors (58.8% variance).
- Energy efficiency factors uniquely contributed 11.2% to the variance, with dorsiflexor weakness, spasticity, metabolic cost, and walking speed being key predictors.
Conclusions:
- Step-length asymmetry in unilateral CP is multifactorial, influenced by both neuromotor and energetic factors.
- While dorsiflexor strength is a key predictor, plantarflexor function remains important.
- Integrated rehabilitation addressing strength, spasticity, and gait efficiency is recommended for optimizing gait symmetry.
Introduction:
Step-length asymmetry is a prevalent, energy-inefficient gait deviation in children with unilateral cerebral palsy (CP). While neuromotor impairments and energy efficiency factors are implicated in gait deviations, their combined predictive power on step-length asymmetry remains poorly understood.
Objective:
This study aimed to quantify the independent and synergistic predictive roles of specific neuromotor constraints and energetic efficiency variables in explaining step-length asymmetry in this population.
Methods:
Fifty-two children with unilateral CP (aged 8-18 years; Gross Motor Function Classification System levels I - II) participated. Step-length asymmetry was defined as the absolute percentage difference between affected and less-affected limb step lengths, normalized to their mean. Neuromotor function was assessed through dorsiflexor strength, plantarflexor dynamic spasticity slope, passive dorsiflexion range, and ankle proprioceptive acuity. Energetic efficiency was evaluated using the metabolic cost of walking and self-selected walking speed.
Results:
Hierarchical multiple linear regression demonstrated that the final model, incorporating neuromotor impairments and energy efficiency factors, accounted for 70% of the total variance in step-length asymmetry (R2 = 0.70, p < .001). Neuromotor impairments were primary drivers, explaining 58.8% of the variance (R2 = 0.588, p < .001), but adding energy efficiency factors provided a unique, statistically significant predictive contribution of 11.2% (ΔR2 = 0.112, p = .0008). The strongest individual predictors of step-length asymmetry were dorsiflexor weakness, dynamic spasticity slope, metabolic cost of walking, and self-selected walking speed.
Conclusion:
Step-length asymmetry in unilateral CP is a multifactorial phenomenon significantly predicted by specific neuromotor and energy efficiency factors. Importantly, the statistical dominance of dorsiflexor strength in our specific model should not be misconstrued as a clinical directive to deprioritize plantarflexor strengthening, given the undeniable biomechanical role of the plantarflexors in forward propulsion and contralateral step length. Nonetheless, these findings underscore the need for integrated rehabilitation strategies that simultaneously target dorsiflexor strength, dynamic spasticity, and gait efficiency (including walking speed and metabolic economy) to optimize gait symmetry and function in this population.
