Fig 1.
Causal model (portrayed as a directed acyclic graph) of the potential contributors to high metabolic power during walking in children with cerebral palsy (CP).
The initial brain injury is colored white to represent an unmeasured factor. Despite being unmeasured, including the initial brain injury helps to simplify the complex relationship between neurological impairments in CP. Blue nodes are factors often treated and measured in the clinic (neurological and physical impairments), so understanding their effects offers a better understanding of their importance in treating metabolic power. Metabolic power, colored in black, is the outcome of interest. Gray variables are potential confounders.
Table 1.
Participant characteristics.
Table 2.
Adjustment sets necessary to minimize confounding bias.
Fig 2.
Accumulated local effects plot of the total causal effects of gait deviation index, selective motor control, dynamic motor control, spasticity, and strength on metabolic power with 95% bootstrapped confidence intervals.
These plots represent the average change in metabolic power that can be expected with a change in the x-axis variable. X-axis variables are normalized as z-scores, where more positive scores indicate a lesser severity of impairment (i.e., more typical gait, more coordinated, less spastic, stronger). Rug plots along the x-axis display the distribution of scores for each impairment. The bottom left scale indicates how large a single standard deviation is with respect to original units.
Fig 3.
The range of the causal effect for each factor for the middle 95th percentile.
The dotted and dashed lines show the 25th percentile and median metabolic power of children included in this study. The total effect of GDI is approximately twice that of SMC and DMC, and more than thrice that of spasticity or strength.