Incomplete atypical femoral fractures after bisphosphonate use in postmenopausal women.

Purpose: This study aimed to determine the prevalence of incomplete atypical femoral fractures (iAFFs) in postmenopausal women using bisphosphonates and to investigate the potential risk factors for the development of iAFF.

Methods: The national health-care records system indicated that 2746 postmenopausal women in our region aged ≥50 years were taking bisphosphonates. Using an assumed iAFF prevalence of 10% and levels of 5% significance and ±5% precision, we calculated that a sample size of 132 participants was needed for this study. The patients were randomly selected and invited to the hospital. Radiographs and bone scans were used to evaluate each patient for iAFF. Bone mineral density, 25-hydroxy vitamin D, parathyroid hormone, and alkaline phosphatase measurements were performed.

Results: The mean age of the study population was 72.79 ± 7.35 years, and the mean duration of bisphosphonate use was 7.7 ± 3.4 years. We found iAFF in 14 (10.6%) patients, and 3 patients had bilateral involvement. Of the 17 femurs with iAFF, a proximal third location was seen in 2 patients (11.8%), a mid-third location in 14 (82.4%), and a distal third location in 1 (5.9%). The duration of bisphosphonate use was longer, and parathyroid hormone levels were higher in patients with iAFF compared to those without an incomplete fracture.

Conclusion: We found a relatively higher prevalence of iAFF in postmenopausal women using bisphosphonate. Early identification and treatment of iAFF is crucial for reducing potential patient morbidity and hospital costs.