Association between femoral localized cortical thickening ("beaking" or "flaring") and bisphosphonate duration in glucocorticoid-induced osteoporosis.

Abstract

Introduction: Glucocorticoid-induced osteoporosis (GIOP) is the most common form of secondary osteoporosis, and bisphosphonates (BPs) are widely used for treatment. Localized cortical thickening (LCT, "beaking" or "flaring") is a characteristic radiographic finding and a potential precursor of atypical femoral fracture, a known complication of long-term BP use. The incidence of LCT and its association with BP duration in GIOP remain unclear.

Materials and methods: In this cross-sectional study, 86 outpatients with GIOP (mean age, 60.6 years; 62.8% women) were included. Femoral radiographs were evaluated for LCT, cortical thickness index (CTI; diaphyseal/subtrochanteric), and lateral bowing angle (LBA). Patients were stratified by BP duration (≥2 or ≥4 years), and 1:1 propensity score matching was used to evaluate the association with LCT. Associations of BP duration with CTI and LBA were analyzed using linear mixed-effects models; correlations with bone turnover markers (BTMs) and bone mineral density (BMD) were also examined.

Results: LCT was observed in 11 (12.8%) patients, including 10 undergoing BP therapy. Patients with LCT had a significantly longer duration of BP use (median: 8.0 years vs. 1.2 years, p <0.01). After matching, BP use for ≥4 years was significantly associated with LCT (odds ratio=11.29, p=0.01), whereas that for ≥2 years was not. Diaphyseal CTI significantly increased with BP duration; no associations were found with subtrochanteric CTI, LBA, BTMs, or BMD.

Conclusion: In GIOP, prolonged BP use, especially for ≥4 years, was associated with LCT and greater diaphyseal cortical thickness. Radiographic assessment is essential in patients with GIOP and long-term BP use.