Fracture risk following an atypical femoral fracture
J Bone Miner Res. 2021 Oct 20 doi: 10.1002/jbmr.4461. Online ahead of print.
Atypical femoral fractures (AFF) occurring during the course of osteoporosis treatment usually lead to anti-resorptive (AR) drugs discontinuation. However, the risk of fracture after an AFF is unknown. We conducted a follow-up study of patients with AFF matched 1:3 for age- and gender with patients with a peripheral major osteoporotic fracture (pMOF), in the setting of a fracture liaison service, to investigate the incidence of subsequent low-trauma fractures. Fifty-five patients with AFF (95% women, age (mean ± SD) 75 ± 10 years, 89% exposed to AR drugs), followed for 6.2 ± 3.7 years, were compared to 165 matched controls with a pMOF (hip 85%) followed for 4.3 ± 2.6 years. During the follow-up, 38% of patients in the AFF group and 16% in the pMOF group received AR therapies. Continuation of AR drugs after an AFF was associated with contralateral AFF in 27% of subjects. The risks of new low-trauma, major osteoporotic and imminent (within 2 years) fractures, were similar between the two groups: incidence rate ratio (95% CI) of subsequent fracture following AFF relative to pMOF, 1.30 (0.82, 2.04), 1.28 (0.74, 2.15) and 1.11 (0.54, 2.15), respectively. Moreover, the risk of sustaining multiple fractures per participant was significantly increased among patients with AFF compared to pMOF (hazard ratio 1.48 (1.00, 2.19); p = 0.049). When taking mortality into account, the risk of subsequent fractures tended to be higher in the AFF group (sub-hazard ratio 1.42 (0.95, 2.12)). In conclusion, patients who sustained an AFF are at high risk of subsequent fragility fractures, at least equal or even greater to the risk observed after a pMOF. However, continuation of AR drugs increases the risk of contralateral AFF. Therefore, optimal modalities for secondary fracture prevention after AFF require further evaluation. This article is protected by copyright. All rights reserved.