Combined effects of leg length discrepancy and the addition of distal mass on gait asymmetry.

Asymmetries in gait often arise due to some form of physical impairment. For example, a leg length discrepancy (LLD) or the change of limb mass can result in asymmetric gait patterns. Although adding mass and LLD have been studied separately, this research studies how gait patterns change as a result of asymmetrically altering both leg length and mass at a leg's distal end. Spatio-temporal and kinetic gait measures are used to study the combined asymmetric effects of placing LLD and mass on the opposite and same side. There were statistically significant differences for the amount of mass and leg length added for all five parameters. Contrary to our hypothesis, there was no significant interaction between the amount of mass and leg length added. There were cases in all perturbations where a combination of mass and LLD make a gait parameter more symmetric than a single effect. These cases exhibit the potential for configurations with lower overall asymmetries even though each parameter has a slight asymmetry as opposed to driving one parameter to symmetry and other parameters to a larger asymmetry.

Combined gait asymmetry metric.

People with physical impairments often have asymmetric gait. To evaluate if their overall symmetry is improving during intervention, there needs to be a simple metric that can help classify gait patterns that includes multiple measures of gait asymmetry. The Combined Gait Asymmetry Metric presented here is based on the Mahalanobis distance of multiple step parameters. We tested able-bodied subjects with perturbations that involve a change in leg length, the addition of ankle weights, and a combination of both perturbations. The Mahalanobis distances are calculated from perfect symmetry to all points in the data to analyze the effects of the different perturbations. The metric demonstrates how an overall view of symmetry can give a better perspective of asymmetry than only looking at a few individual parameters. This metric is straightforward and can be extended to include large numbers of spatiotemporal, kinematic, and kinetic parameters that more completely evaluate a change in gait symmetry.