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Hip Moment Prediction with a Subset of Inverse Dynamics Components: 2609 Board #129 June 2 9

PURPOSE: Joint moments, calculated via inverse dynamic (ID) analyses, represent the net effect of all forces spanning a joint, and are used as a surrogate to represent joint demand and are used to describe movement patterns. However, because excessive instrumentation is required, ID analyses are rarely used outside of a laboratory setting. Insight into joint moments using simply collected quantitative measures has the potential to impact a variety of settings (e.g. movement retraining, sports performance, etc.). Therefore, the objective of this study was to determine if hip moment could be predicted using a subset of ID analysis components. METHODS: Kinematic and force platform data were captured for 12 healthy subjects (9M/3F, age: 59.8 ± 7.8 yrs, BMI: 25.1 ± 2.9) walking at 1m/s. Sagittal-plane hip moment during stance period was calculated using ID analysis. Pearson correlations (r) were calculated at every percentage of the stance period between the hip moment and the kinetic components (MMK, MKy, MKx, Mg) and inertial components (May, Max, MIα) of the thigh from the ID calculations (Fig. 1a). 95% confidence intervals that did not cross zero were considered to be significant, and mean correlations throughout stance were calculated. RESULTS: Hip moment was highly correlated (r = 0.93) with MKy, the moment due to vertical joint reaction force at the knee for 94.4% of the stance period and highly negatively correlated (r = -0.83) with Mg, the moment due to gravity. Inertial components of the thigh were not correlated with hip moment. CONCLUSIONS: The results indicate that hip moment can be predicted with vertical knee joint reaction force and thigh orientation. Because the moment due to the vertical reaction force at the knee is dominated by the ground reaction force, this can be estimated using instrumented insoles. In summary, the hip moment during stance shows promise for being predicted with simple regression equations and minimal instrumentation.