2019 ISCD Official Position Detection of Atypical Femur Fractures Angela M. Cheung, 1,2, * Malachi J. McKenna, 3,4 Denise M. van de Laarschot, 5 M. Carola Zillikens, 5 Valerie Peck, 6 Jeevitha Srighanthan, 1,2 and E. Michael Lewiecki 7 1 Centre of Excellence in Skeletal Health Assessment, University of Toronto, Toronto, Ontario, Canada; 2 Osteoporosis Program, University Health Network and Sinai Health System, Toronto, Ontario, Canada; 3 DXA Unit, St. Vincent’s University Hospital, Dublin, Ireland; 4 School of Medicine and Medical Sciences, University College Dublin, Dublin, Ireland; 5 Bone Centre, Department of Internal Medicine, Erasmus University Medical Centre, Rotterdam, the Netherlands; 6 Osteoporosis and Metabolic Bone Disease Program, Department of Medicine, NYU Langone Health, New York, NY, USA; and 7 New Mexico Clinical Research & Osteoporosis Center, Albuquerque, NM, USA Abstract The 2019 International Society for Clinical Densitometry (ISCD) Position Development Conference Task Force for monitoring with dual-energy X-ray absorptiometry (DXA) identified detection of atypical femur fractures (AFFs) as an important topic and established this working group to answer key questions in this area. The authors conducted a systematic review of the literature and deliberated on proposed ISCD positions, which were then reviewed by an external expert panel and vetted at the 2019 ISCD Position Development Conference in Kuala Lumpur on March 23, 2019. This paper summarizes the final ISCD positions and the rationale for supporting these positions. Default-length femur imaging or extended-length femur imaging as well as full-length femur imaging (FFI), both single-energy and dual-energy scans, by DXA can detect abnor- malities in the spectrum of AFF. It is important to visually inspect all DXA scans of the hip and femur, and report on findings of focal periosteal and endosteal thickening at the lateral cortex (grade: Good, A, W). FFI is the preferred DXA scan mode for detecting abnormalities in the spectrum of AFF. The FFI report should state the absence or presence of abnormalities in the spectrum of AFF. If focal thickening is present on the lat- eral cortex, the report should state whether a lucent line is seen (grade: Fair, C, W). The ISCD recommends considering the use of bilateral FFI in patients who are currently or have been in the past year on potent anti- resorptive therapy (ie, oral or intravenous bisphosphonate or subcutaneous denosumab therapy) for a cumula- tive period of 3 or more years, especially those on long-term glucocorticoid therapy (grade: Fair, B, W). More research is needed to determine the role of repeat testing and the optimal time interval for follow-up DXA scans, whether an automated measuring tool would perform better than visual inspection, whether FFI would change patient management and outcomes, and the cost-effectiveness of FFI. Key Words: Atypical femur fracture; DXA; full-length femur imaging; monitor; osteoporosis. Introduction The role of dual-energy X-ray absorptiometry (DXA) systems in the recognition of incomplete atypical femur fracture (iAFF) was first described by McKiernan, who published serial DXA images of default-length femur Received 07/02/19. Accepted 07/08/19. *Address correspondence to: Angela M. Cheung, MD, PhD, University Health Network, 200 Elizabeth Street, 7 Eaton North, Room 221, Toronto, Ontario M5G2C4, Canada E-mail: angela.cheung@uhn.ca 506 Journal of Clinical Densitometry: Assessment & Management of Musculoskeletal Health, vol. 22, no. 4, 506À516, 2019 Ó 2019 Published by Elsevier Inc. on behalf of The International Society for Clinical Densitometry. 1094-6950/22:506À516/$36.00 https://doi.org/10.1016/j.jocd.2019.07.003