Bilateral symmetry in leg and joint stiffness in children with spastic hemiplegic cerebral palsy during gait

Using bilateral data in controls and patients with bilateral and unilateral pathology requires increased scrutiny

In many aspects of human research, capturing multiple measures from the same participant is common due to the symmetric nature of the human body (e.g., two eyes, ten fingers, two legs, etc.). This has established a concerning paradox in biomedical and clinical research. When the same condition exist bilaterally (controls or bilateral pathology), researchers often blindly include both (or multiple) measures into the statistical analysis. This assumes that measures between the two sides are statistically independent (uncorrelated). However, there are certain inherent factors within an individual (e.g., age, sex, physical activity, gait pattern, tissue characteristics, hormonal status, pain thresholds, etc.) that would point to a statistical dependence between bilateral measures. Conversely, in unilateral pathology, it is common practice to use the contralateral side as the comparator. This assumes the exact opposite, that sans pathology, bilateral measures are perfectly correlated without bias. Both of these assumptions can lead to errors in the study conclusions. Few studies have explored the statistical dependence between multiple measures from the same participant. Thus, the purpose of this perspective is to explore the statistical considerations associated with analyzing multiple measures from the same participant and provide recommendations for navigating the use of multiple, non-temporal, data points from the same participant. To give context for these recommendations, an example dataset involving patellofemoral kinematics is provided. Due to the prevalent use of bilateral data in the current literature and the resulting potential for invalid study conclusions, we recommend that future research use caution when using multiple measures from the same participant and apply proper statistical analysis (e.g., generalized estimating equations) when these measures are not independent. If the contralateral limb is used as a comparator in unilateral pathology, strong evidence must exist that the underlying pathology has not altered the measures of interest in this contralateral limb.

Asymmetry in sensory-motor function between the lower limbs in children with hemiplegic cerebral palsy: An observational study

The objective of this study was to examine the difference in sensory-motor impairments (i.e., balance, contracture, coordination, strength, spasticity, and sensation) between legs in children with hemiplegic cerebral palsy. An observational study measured both lower limbs of children with hemiplegic cerebral palsy over one session. Six sensory-motor impairments (balance, coordination, strength, spasticity, contracture, and proprioception) were measured. The between-leg differences were analyzed using the paired t-tests and presented as the mean differences (95% confidence interval (CI)). Twenty-four participants aged 10.3 years (standard deviation: 1.3) participated. The affected leg was less than the less-affected leg in terms of the strength of dorsiflexors (mean difference (MD) -2.8 Nm, 95% CI -4.2 to -1.4), plantarflexors (MD -2.6 Nm, 95% CI -4.1 to -1.0), knee extensors (MD -5.3 Nm, 95% CI -10.2 to -0.5) as well as range of ankle dorsiflexion (MD -8 deg, 95% CI -13 to -3), and balance (median difference -11.1, 95% CI -11.6 to -10.6). There was a trend toward a difference in terms of the strength of hip abductors (MD -2.6 Nm, 95% CI -5.3 to 0.1) and coordination (MD -0.20 taps/s, 95% CI -0.42 to 0.01). The legs were similar in terms of the strength of hip extensors (MD 0.3 Nm, 95% CI -4.7 to 5.3), proprioception (MD 1 deg, 95% CI 0 to 2), and spasticity (median difference 0, 95% CI 0 to 0). Examination of the difference in sensory-motor impairments between legs in children with hemiplegic cerebral palsy has given us some insights into the deficits in both legs. Not only was balance, strength, and coordination decreased compared with the less-affected leg but also the less-affected leg was markedly decreased compared with typically developing children. Therefore, an intervention aimed at increasing muscle strength and coordination in both legs might have a positive effect, particularly on more challenging physical activities. This may, in turn, lead to successful participation in mainstream sport and recreation.

Impacts of Motor Developmental Delay on the Inter-Joint Coordination Using Kinematic Synergies of Joint Angles During Infant Crawling

Motor developmental delay (MDD) usually affects the inter-joint coordination for limb movement. However, the mechanism between the abnormal inter-joint coordination and MDD is still unclear, which poses a challenge for clinical diagnosis and motor rehabilitation of MDD in infant's early life. This study aimed to explore whether the joint activities of limbs during infant crawling are represented with kinematic synergies of joint angles, and evaluate the impacts of MDD on the inter-joint coordination using those synergies. 20 typically developing infants, 16 infants at risk of developmental delay, 11 infants at high risk of developmental delay and 13 infants with confirmed developmental delay were recruited for self-paced crawling on hands and knees. A motion capture system was employed to trace infants' limbs in space, and angles of shoulder, elbow, hip and knee over time were computed. Kinematic synergies were derived from joint angles using principal component analysis. Sample entropy and Spearman's rank correlation coefficients were calculated among those synergies to evaluate the crawling complexity and the symmetry of bilateral limbs, respectively. We found that the first two synergies with different contributions to the crawling movements sufficiently represented the joint angular profiles of limbs. MDD further delayed the development of motor function for lower limbs and mainly increased the crawling complexity of joint flexion/extension to some extent, but did not obviously change the symmetry of bilateral limbs. These results suggest that the time-varying kinematic synergy of joint angles is a potential index for objectively evaluating the abnormal inter-joint coordination affected by MDD.