Prevalence of incomplete atypical femoral fractures using single energy absorptiometry after long-term anti-resorptive therapy

Atypical femur fractures (AFFs) have been reported with long-term use of anti-resorptive drugs. Early identification is crucial because it allows early intervention to stop the progression to complete fracture, thus potentially reducing the ensuing burden. It has been shown that extending the scan image to take a full-length image of the femur (FFI) using single energy (SE) X-rays at the time of a dual-energy X-ray absorptiometry (DXA) scan can detect findings in the spectrum of AFF. Following the International Society for Clinical Densitometry (ISCD) recommendations, FFI by SE X-ray is being performed for all patients who present to the Calcium Metabolism and Osteoporosis program at AUBMC for bone mineral density measurement by DXA, if they have received anti-resorptive drug for a cumulative period of 3 years or more. Patients can be currently on anti-resorptive drug or have discontinued it within the past 5 years prior to scan, instead of the 1 year, as recommended by the ISCD. The primary aim of this retrospective study was to assess the prevalence of findings in the spectrum of AFF using FFI by SE X-rays. We collected data on demographic factors, clinical risk factors for osteoporosis, and bone densitometry parameters. Out of the 948 patients, 18 patients were found to have findings in the spectrum of AFF; 14 underwent subsequent imaging studies to investigate and confirm these abnormalities. One patient out of 948 patients was found to have an incomplete AFF confirmed by computed tomography scan. Studying the prevalence of the signs of AFF on FFI in other studies and assessing the specificity of this technique by comparing its findings with more established methods is important. Future ISCD task forces may need to reassess efficacy and cost effectiveness of its recommended guidance on using SE femur in patients to prevent adverse outcomes.