Head and Trunk Moments of Inertia of Able-Bodied and Unbraced Scoliotic Girls

Abstract

Objective: The purposes of this study were to estimate head and trunk’s (HT) radii of gyration (K) and moments of inertia (I) in able-bodied and unbraced scoliotic girls using an angular momentum method, to test if the use of mean ratios calculated in this study and given by de Leva present similar values compared to the experimental data, and to determine how these methods behave in estimation of scoliotic HT’s K and I with variable Cobb angles. Background: Scoliotic HT’s I estimated from anthropometric tables can lead to error in joint muscle moment calculations. Method: Twenty-one unbraced scoliotic and 20 able-bodied girls participated. HT’s I values were calculated using an angular momentum method. Results: Angular momentum method provided greater HT’s I for the scoliotic group compared with the able-bodied girls. HT’s I obtained by the mean ratios calculated from this study were close to the measured values. Compared with the experimental I, de Leva method provided significantly lower I in the scoliotic group. Scoliotic HT’s K and I obtained from angular momentum method showed greater correlations with the Cobb angles. Conclusion: The use of mean ratios obtained in this study to estimate HT’s K values in unbraced scoliotic girls could overcome the drawbacks of current anthropometric methods. Application: These results can be used to calculate more precise moments of force during daily activities in scoliotic girls with mild scoliosis and to improve the design of corrective flexible body braces prescribed in cases of rapid interventions in young patients of moderate spinal deformities.