The Effect of Long- Term Alendronate Treatment on the Cortical Thickness Ratio of the Proximal Femur

INTRODUCTION: Alendronate (Aln) is a bisphosphonate agent that has been widely used for the treatment of osteoporosis. Recently, several studies have suggested an association between long-term use of Aln and the occurrence of low-energy subtrochanteric/femoral shaft (ST/FS) fractures. Previous studies described characteristic imaging features of this atypical fracture including transverse orientation of the fracture line, beaking of the cortex on one side, and cortical hypertrophy. The thickening of femoral cortex is believed to be a result of an impaired ability of bone treated with Aln to remodel, leading to an accumulation of microdamages and compromised bone strength. The potential predisposition toward cortical thickening in patients with long-term Aln therapy however remains unknown. To address this question, we conducted a study to evaluate the effects of prolonged Aln treatment on cortical thickness of the proximal femur. We hypothesized that longterm Aln use greater than 5 years results in increased cortical thickness at the ST region of the proximal femur.