Evaluation of the Nature and Etiologies of Risk Factors for Diaphyseal Atypical Femoral Fractures

Abstract

Objectives: Differences in the mechanisms of subtrochanteric and diaphyseal atypical femoral fractures (AFFs) have been speculated in studies that have analyzed differences in the patients’ backgrounds. However, the etiologies of each type of AFF have not been investigated in detail. Therefore, this study aimed to investigate the nature and etiologies of the risk factors for diaphyseal AFFs. Materials and Methods: Eighty consecutive Japanese patients with 91 diaphyseal AFFs (the AFF group) and 110 age-matched female patients with osteoporosis (the non-AFF control group) were included. Their clinical data were compared and the factors affecting AFFs were investigated. Furthermore, the etiologies of the risk factors for diaphyseal AFFs were examined. Results: Multivariate analysis revealed that femoral serrated changes, bisphosphonate or denosumab usage, and lateral and anterior femoral curvatures were the risk factors for diaphyseal AFFs (p<0.0011, p=0.0137, and p<0.0001, respectively). Multivariate analyses also revealed that serrated changes and low serum 25(OH)D levels affected the lateral curvature (p=0.0088 and 0.0205, respectively), while serrated changes affected the anterior curvature (p=0.0006); each significantly affected the femoral curvature. In addition, a high serum calcium (Ca) level, lateral femoral curvature, and anterior femoral curvature were the predictors of serrated changes (p=0.0146, 0.0002, and 0.0098, respectively). Conclusion: The risk factors for diaphyseal AFFs were bone resorption inhibitor usage, a strong femoral curvature, and serrated changes. A low serum 25(OH)D level and serrated changes are the risk factors for lateral curvature, while a high serum Ca level is a risk factor for serrated changes.

Factors Affecting the Second Complete Atypical Femoral Fracture after the First Atypical Fracture

“…The radiographic findings of the femur were evaluated in detail by dividing them into three categories: focal cortical thickening of the lateral cortex; fracture line of lateral cortex; serrated changes ( Fig. 2 ) [ 12 ]. We measured the curvature of the femur using anteroposterior and lateral radiographs per the method described by Yau et al [ 13 ].…”

Towards understanding how bisphosphonate‐dependent alterations to nutrient canal integrity can contribute to risk for atypical femoral fractures: Biomechanical considerations and potential relationship to a real‐world analogy

“…Interestingly, the risk posed by progressive stress concentration would be further accentuated in those with a bowed femur, individually at higher risk for developing an AFF. [ 32 ] Because of the bowing, the stress concentration around the nutrient canals modified in response to BP exposure would be amplified. Thus, the stress concentrations around the nutrient canal defects in the load distribution may progress until a threshold is reached, dependent on the type of BP used and the time on the drug, at which point a slight deviation in an everyday loading environment may trigger the rare event labeled an AFF.…”