Effect of morphology and cortical thickness variations on tibial strains in different movements.

Morphology and cortical thickness of tibia bone influence the strength and strain distribution of bone and also influence fatigue fracture risk. However, current studies have not extensively explored the effect of morphology and cortical thickness on tibial strain distribution during different activities. This study aims to assess the effect of tibial morphology and cortical thickness on tibial strain during six different sports movements. The tibial surfaces were reconstructed from 40 males' CT data, with cortical thickness assessed at the outer surface. A statistical shape model captured main variations in tibial morphology and cortical thickness. Finite Element models were created by scaling the mean shape along the first four principal components. Muscle and joint forces from different activities were calculated using static optimization and joint reaction analysis and applied to the models, assessing strained volume and peak strain at middle and distal tibia. The first four principal components accounted for 87 % of the total cumulative variance. Perturbations in the second principal components resulted in the greatest relative differences in peak mid-tibia tensile (128 %) and distal-tibia compressive (160 %) strain during sidestep cutting, but perturbations in the first principal components resulted in the greatest relative differences during other activities (70 %∼118 %, 107 %∼129 %). Perturbations in the first four principal components resulted in the small relative differences in strained volume during walking (-9%∼5%). For runners, tibial size and cortical thickness are more related to tibial fatigue fracture risk, whereas for athletes with frequent directional changes, like basketball players, the tibial shaft size is more relevant.