Sclerotic lines around the radial tuberosity of the proximal radius in patients with atypical femoral fractures associated with long-term bisphosphonate use: a preliminary report

Purpose: Sclerotic lines have been detected at specific locations on the forearm and metaphysis of the lower extremities (femur and tibia) in some patients with atypical femoral fractures (AFFs) associated with long-term bisphosphonate (BP) use. Herein, we present our preliminary data relating to the factors associated with the occurrence of sclerotic lines in patients diagnosed with AFFs. Methods: We inspected the clinical charts of patients who were prescribed BPs at our institution between 2010 and 2020. Fifty-six patients were finally investigated, including patients with sclerotic line lesions at the radial tuberosity (21 patients), and those without any pathognomonic lesions on either radius on a simple radiograph (35 patients). Results: No significant between-group differences in basic demographic characteristics, bone mineral density, or the total period of BP administration were observed (p>0.05). Multivariate analyses of the variables that exhibited significant between-group differences in the univariate analyses demonstrated that the time since the last BP administration at the time of AFF diagnosis (odds ratio [OR], 0.441) and the concurrent presence of similar lines on the femur (OR, 36.00) were significantly associated with the presence of sclerotic lines on the proximal radius. The cutoff time after the last BP administration at the time of AFF diagnosis was 16.5 months, which may serve as a predictor for the development of a sclerotic line around the radial tuberosity.Conclusion: Sclerotic lines on the proximal radius were detected more frequently in patients who had been recently treated with a BP or had similar lines on the lower extremities.