Background/Purpose

Although the use of bisphosphonates has been shown to reduce vertebral and proximal femur fracture risk in patients with osteoporosis, current evidence suggests that there is an association between bisphosphonate use and atypical femoral fractures (AFFs). However, the extent of this risk remains unclear, especially in Asian population. In this study, we aimed to estimate the proportion of AFFs among total patients with femoral fractures and to compare the characteristics of patients with AFFs with that of patients with classic femoral fractures (CFFs).

Methods

Between 2003 and 2013, a total of 578 female patients with low-energy femoral fractures who had been hospitalized at an Asian single university hospital were retrospectively enrolled. Radiographs and medical records were reviewed by medical doctors. Patients were classified into two groups according to the site of fracture: AFF group for patients with subtrochanteric or diaphyseal femoral fractures and CFF group for patients with intertrochateric or neck fractures. After estimating the prevalence of AFF among patients with low-energy femoral fractures, we assessed the association of bisphosphonate use and AFFs with using multivariate logistic regression analysis.

Results

Twenty-seven patients (4.7%) with AFFs and 551 patients (95.3%) with CFFs were identified. Of the patients with AFFs, 11 (40.7%) had been treated with bisphosphonates compared with 40 (7.3%) in the CFF group. Patients with AFFs were younger than CFFs group (71.2 ± 9.5 vs. 76.9 ± 8.7, p<0.01). Without correction for age, patients with AFFs appeared to have a higher cortical thickness index (1.1 ± 0.4 vs. 0.98 ± 0.4, p<0.05) compared to patients with CFFs. With adjusting the age, body mass index, types of injury (slip or fall), and history of rheumatoid arthritis, bisphosphonate was the only predictor for atypical fractures (OR 9.8, CI 3.7-26.4). Among the patients with using bisphosphonate when they fractured (n=44), the proportion of AFFs was nearly 21% (n=9). The proportions of AFFs among femoral fractures were increased according to the duration of bisphosphonate; 15.4% (6 among 39 patients) in patients with less than 5 years and 60% (3 among 5 patients) in patients over 5 years, respectively.

Conclusion

The proportion of AFFs was around 5% among the patients with femoral fractures and AFF were associated with bisphosphonate use in Asian ethnicity. Longer duration of treatment resulted in augmented risk, though any period in bisphosphonate use could cause atypical femur fracture.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-and-associating-factors-with-atypical-femoral-fractures-an-asian-single-center-based-case-control-study/