Femur geometry influences atypical femoral fracture location.

Abstract

Bone geometry is thought to be an important factor in the development of atypical femoral fracture. Our three-dimensional analysis of whole-femur geometry indicates that lateral bowing influences fracture location. Lateral bowing may indeed play a role in AFF pathophysiology. Atypical femoral fracture (AFF) is a low-energy fracture of the diaphyseal, distal femoral, or subtrochanteric regions. Lower limb geometry may be an important factor in the development of AFF, but studies to date have been limited to a handful of simple discrete measurements. The purpose of this study was to evaluate variations in whole-bone geometry in patients with AFF and to determine whether geometry variations were associated with AFF location using statistical shape modeling. Computed tomography scans of fifty-seven AFF patients were used to create a statistical shape model. Principal component scores and discrete measures were compared between patients with subtrochanteric and midshaft AFF. Two principal component scores, both characterizing variations in lateral bowing and anteversion, distinguished between fracture location (p ≤ 0.005). Principal component scores indicating greater lateral bowing and less anteversion were moderately correlated with more distal fracture locations (PC 1: r = 0.41, p = 0.001; PC 3: r = 0.48, p < 0.001). Interestingly, anterior bowing was not different between fracture locations. Our three-dimensional analysis of whole femur geometry indicates that lateral bowing influences fracture location and may play a role in AFF pathophysiology.