Atypical femoral fractures (AFFs) are uncommon and have been associated particularly with long‐term antiresorptive therapy, including bisphosphonates. Although the pathogenesis of AFFs is unknown, their identification in bisphosphonate‐naïve individuals and in monogenetic bone disorders has led to the hypothesis that genetic factors predispose to AFF. Our aim was to review and summarize the evidence for genetic factors in individuals with AFF. We conducted structured literature searches and hand‐searching of conference abstracts/reference lists for key words relating to AFF and identified 2566 citations. Two individuals independently reviewed citations for (i) cases of AFF in monogenetic bone diseases and (ii) genetic studies in individuals with AFF. AFFs were reported in 23 individuals with the following 7 monogenetic bone disorders (gene): osteogenesis imperfecta (COL1A1/COL1A2), pycnodysostosis (CTSK), hypophosphatasia (ALPL), X‐linked osteoporosis (PLS3), osteopetrosis, X‐linked hypophosphatemia (PHEX), and osteoporosis pseudoglioma syndrome (LRP5). In 8 cases (35%), the monogenetic bone disorder was uncovered after the AFF occurred. Cases of bisphosphonate‐naïve AFF were reported in pycnodysostosis, hypophosphatasia, osteopetrosis, X‐linked hypophosphatemia, and osteoporosis pseudoglioma syndrome. A pilot study in 13 AFF patients and 268 controls identified a greater number of rare variants in AFF cases using exon array analysis. A whole‐exome sequencing study in 3 sisters with AFFs showed, among 37 shared genetic variants, a p.Asp188Tyr mutation in the GGPS1 gene in the mevalonate pathway, critical to osteoclast function, which is also inhibited by bisphosphonates. Two studies completed targeted ALPL gene sequencing, an ALPL heterozygous mutation was found in 1 case of a cohort of 11 AFFs, whereas the second study comprising 10 AFF cases did not find mutations in ALPL. Targeted sequencing of ALPL, COL1A1, COL1A2, and SOX9 genes in 5 cases of AFF identified a variant in COL1A2 in 1 case. These findings suggest a genetic susceptibility for AFFs. A large multicenter collaborative study of well‐phenotyped AFF cases and controls is needed to understand the role of genetics in this uncommon condition. © 2017 The Authors JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Context Atypical femur fractures (AFFs) are serious adverse events associated with bisphosphonates and often show poor healing. Evidence acquisition We performed a systematic review to evaluate effects of teriparatide, raloxifene, and denosumab on healing and occurrence of AFF. Evidence synthesis We retrieved 910 references and reviewed 67 papers, including 31 case reports, 9 retrospective and 3 prospective studies on teriparatide. There were no RCTs. We pooled data on fracture union (n = 98 AFFs on teriparatide) and found that radiological healing occurred within 6 months of teriparatide in 13 of 30 (43%) conservatively managed incomplete AFFs, 9 of 10 (90%) incomplete AFFs with surgical intervention, and 44 of 58 (75%) complete AFFs. In 9 of 30 (30%) nonoperated incomplete AFFs, no union was achieved after 12 months and 4 (13%) fractures became complete on teriparatide. Eight patients had new AFFs during or after teriparatide. AFF on denosumab was reported in 22 patients, including 11 patients treated for bone metastases and 8 without bisphosphonate exposure. Denosumab after AFF was associated with recurrent incomplete AFFs in 1 patient and 2 patients of contralateral complete AFF. Eight patients had used raloxifene before AFF occurred, including 1 bisphosphonate-naïve patient. Conclusions There is no evidence-based indication in patients with AFF for teriparatide apart from reducing the risk of typical fragility fractures, although observational data suggest that teriparatide might result in faster healing of surgically treated AFFs. Awaiting further evidence, we formulate recommendations for treatment after an AFF based on expert opinion.

Atypical femur fractures (AFFs) are a rare but serious complication associated with the use of antiresorptive drugs such as bisphosphonates. Assessment of incomplete AFFs on extended femur scans by dual-energy X-ray absorptiometry (DXA) may prevent the development of complete fractures. The aim of this study was to evaluate the potential of extended femur scans by DXA as a screening tool for incomplete AFFs. From June 2014 until September 2016, extended femur scans were routinely performed in all consecutive patients undergoing DXA scanning who had used bisphosphonates or denosumab at any given moment in the previous year. When "beaking" was found, defined as a localized periosteal or endosteal thickening of the lateral cortex, a radiograph of the femur was performed to confirm incomplete AFF. Beaking was detected in 12 of 282 patients (4.3%) with extended scans of both femora. In 9 patients (3.2%), beaking corresponded with the radiological presence of incomplete AFFs, of whom 4 already had an X-ray made because of a previous complete AFF of the other leg. Five patients (1.8%) were newly diagnosed with 6 yet unknown incomplete AFFs. No additional X-ray was performed in 2 patients because of loss of follow-up. Beaking was explained by known soft tissue calcifications in 1 patient. The positive predictive value of beaking on extended femur scan was 83.3% in our study. Three cases in whom the new diagnosis of incomplete AFF has affected medical and surgical treatment are further discussed to illustrate the relevance of early detection. We conclude that extended femur scans by DXA can detect incomplete AFFs in patients on antiresorptive treatment and should therefore be considered a clinically relevant screening tool because early identification of AFFs has therapeutic consequences. © 2017 American Society for Bone and Mineral Research.

No abstract