A model for understanding the causes and consequences of walking impairments

Abstract

Walking is an important skill with positive impacts on health, function, and well-being. Many disorders impair walking and its positive impacts through a variety of complex and interrelated mechanisms. Any attempt to understand walking impairments, or the effects of interventions intended to treat these impairments, must respect this complexity. Therefore, our main objectives in conducting this study were to (1) propose a comprehensive model for quantifying the causes and consequences of walking impairments and (2) demonstrate the potential utility of the model for supporting clinical care and addressing basic scientific questions related to walking. To achieve these goals, we introduced a model, described by a directed acyclic graph, consisting of 10 nodes and 23 primary causal paths. We gave detailed descriptions of each node and path based on domain knowledge. We then demonstrated the model’s utility using a large sample of gait data (N = 9504) acquired as part of routine care at a regional referral center. We analyzed five relevant examples that involved many of the model’s nodes and paths. We computed causal effect magnitudes as Shapley values and displayed the overall importance of variables (mean absolute Shapley value), the variation of Shapley values with respect to underlying variables, and Shapley values for individual observations (case studies). We showed that the model was plausible, captured some well-known cause-effect relationships, provided new insights into others, and generated novel hypotheses requiring further testing through simulation or experiment. To aid in transparency, reproducibility, and future enhancements we have included an extensively commented Rmarkdown file and a deidentified data set.

Demonstrating the Utility of Instrumented Gait Analysis in the Treatment of Children with Cerebral Palsy

“…Note that the change in foot progression does not necessarily equal the summed derotation magnitudes. The impact of derotations on transverse plane kinematics is known to not be one-to-one [18,26].…”

“…The surgeries we highlight are femoral and tibial derotation osteotomies (FDO and TDO) and the outcome is mean stance-phase foot progression. We choose these two treatments and this outcome for the following reasons: Excessive in- and out-toeing are common in CP and impact both gait biomechanics and patient well-being (body image and self-esteem) [18]. Both FDO and TDO are commonly administered at our center (see Figure 3 below). Both FDO and TDO have large effects at the structural level [3].…”

“…• Excessive in-and out-toeing are common in CP and impact both gait biomechanics and patient well-being (body image and self-esteem) [18]. • Both FDO and TDO are commonly administered at our center (see Figure 3 below).…”

“…• Excessive in-and out-toeing are common in CP and impact both gait biomechanics and patient well-being (body image and self-esteem) [18].…”

Effects of interval treadmill training on spatiotemporal parameters in children with cerebral palsy: a machine learning approach

“…BART is a "sum of trees" regression method capable of modeling relationships between input and response variables with low levels of bias and variance [12]. Prior research has leveraged both DAGs and BART to understand complex factors influencing biomechanics and treatment response in CP [9,[13][14][15]. However, BART modeling informed by DAGs has not been used to model individual treatment responses over time.…”