Impaired geometric properties of tibia in older women with hip fracture history

Introduction The purpose of this study was to evaluate side-to-side differences in tibial mineral mass and geometry after hip fracture, and to assess the determinants of such differences. Methods Thirty-eight 60- to 85-year-old women with a previous hip fracture and twenty-two same-aged control women without fractures participated in the study. Bone characteristics of the distal tibia and tibial shaft of both legs were assessed using pQCT in order to compare the side-to-side differences of tibias between the two groups. Results The subjects with fracture history had significantly (p≤0.05, analysis of covariance) larger side-to-side differences than the controls in tibial shaft BMC (-4.9% vs. -0.5%), cortical area (-5.2% vs. 0.1%) and polar moment of inertia (Ipolar) (-5.6% vs. -0.8%) and in distal tibia BMC (-5.1% vs. -1.4%) and Ipolar (-7.5% vs. -2.4%). In the fracture patients, the side-to-side differences in muscle characteristics explained 23 to 44% of the variances in the side-to-side differences in bone mass and geometry. Conclusions Hip fracture results in reduced bone mass and impaired bone geometry in the tibia of the affected limb in older women. Muscle-induced loading may have a considerable role in the recovery of bone mineral mass and geometry after hip fracture.