Comparison of bone turnover suppression in atypical femoral fractures and osteoporotic hip fractures.

We aimed to compare the extent of bone turnover suppression between patients with atypical femoral fractures (AFFs) and osteoporotic hip fractures (typical femur fractures, TFFs) using a one-to-one matching strategy. A single-center retrospective comparison of females aged ≥ 60 years who underwent operative treatment for AFFs and TFFs between January 2010 and March 2021 was conducted. Demographic characteristics and clinical data including fracture site, past medical history, bone mineral density (BMD), bisphosphonate (BP) medication history, and serum bone turnover marker (BTM) levels were examined. Moreover, we performed a logistic regression analysis to determine the risk factors for AFFs and a one-to-one matched-pair analysis to compare various BTMs. Overall, 336 consecutive females were included: 113 with AFFs and 213 with TFFs. The mean age, BMI, and lowest BMD T-score were 78.6 years, 22.8 kg/m2, and -3.3, respectively. Patients with AFF were younger, had lower BMD, higher BMI, higher prevalence of rheumatoid arthritis, a greater proportion with previous steroid or BP use, and a longer history of BP use than patients with TFF. The 48:48 matched-pair analysis revealed higher serum 25(OH) vitamin-D (30.5 vs 18.2 ng/mL, P < 0.001) and calcium levels (8.8 vs 8.3 ng/dL, P = 0.009) and lower serum CTX levels (0.33 vs 0.54 ng/mL, P = 0.010) in the AFF group than in the TFF group, suggesting a more suppressed bone remodeling. No differences in the other BTM levels were found. Despite identical histories and durations of BP use, the AFF group exhibited lower CTX levels, suggesting more suppressed bone remodeling. This observation leads us to infer that more suppressed bone remodeling, indicated by lower CTX levels, could be linked to the occurrence of AFFs.