Assessment of vertebral fracture risk and therapeutic effects of alendronate in postmenopausal women using a quantitative computed tomography-based nonlinear finite element method

Abstract

A QCT-based nonlinear FEM was used to assess vertebral strength and mechanical parameters in postmenopausal women. It had higher discriminatory power for vertebral fracture than aBMD and vBMD. Alendronate effects were detected at 3 months, and marked bone density increases were noted in juxta-cortical areas compared to inner trabecular areas.

Introduction: QCT-based finite element method (QCT/FEM) can predict vertebral compressive strength ex vivo. This study aimed to assess vertebral fracture risk and alendronate effects on osteoporosis in vivo using QCT/FEM.

Methods: Vertebral strength in 104 postmenopausal women was analyzed, and the discriminatory power for vertebral fracture was assessed cross-sectionally. Alendronate effects were also prospectively assessed in 33 patients with postmenopausal osteoporosis who were treated with alendronate for 1 year.

Results: On the age and body weight adjusted logistic regression, vertebral strength had stronger discriminatory power for vertebral fracture (OR per SD change: 6.71) than areal BMD and volumetric BMD. The optimal point for the vertebral fracture threshold was 1.95 kN with 75.9% sensitivity and 78.7% specificity. At 3 months, vertebral strength significantly increased by 10.2% from baseline. The minimum principal strain distribution showed that the area of high fracture risk decreased. At 1 year, the density of the inner cancellous bone increased by 8.3%, while the density of the juxta-cortical area increased by 13.6%.

Conclusions: QCT/FEM had higher discriminatory power for vertebral fracture than BMD and detected alendronate effects at 3 months. Alendronate altered density distributions, thereby decreasing the area with a high fracture risk, resulting in increased vertebral strength.