To examine the clinical characteristics of atypical femoral fracture (AFF) and to determine the risk factors for and clinical outcomes of AFFs in rheumatoid arthritis (RA) patients treated with bisphosphonates (BPs).
A nested case-control study was conducted using data derived from the medical records of all RA patients treated with BPs at Seoul St. Mary's Hospital, a tertiary rheumatology center, from January 1, 2008 to December 31, 2014. All of the patients with RA and had been treated with BPs for at least 1 year. Ten RA patients with AFF were identified, and each of these patients (cases) was age- and sex-matched with 4 RA patients without AFF (controls).
Five hundred fifty-two RA patients had BP exposure. Of the 10 with AFF, all were female (mean ± SD age 66.3 ± 8.7 years), and 90% of cases involved fracture of the proximal femur. The mean ± SD length of BP exposure in patients with AFF was 7.4 ± 3.2 years. Compared with controls, patients with AFF had a longer exposure to BPs and more often had a femorotibial angle of <175 degrees (both P < 0.001). There were no differences in RA duration, medications taken during the previous 6 months, and bone mineral density in the femur and lumbar spine between patients with and those without AFF. Multivariate logistic analyses identified longer BP exposure (odds ratio 2.386 [95% confidence interval 1.066-5.343]) as being associated with an increased risk of AFF.
RA patients who have a valgus deformity and are receiving long-term BP treatment are at higher risk of AFF compared with matched control patients with RA. These patients should be carefully followed up with hip radiography or dual x-ray absorptiometry.