Preoperative Computed Tomography Aortic Calcification and Attenuation of the Vertebral Body Predict Fractures Post‐Kidney Transplantation Using Machine Learning
Mitsuru Tomizawa, Shunta Hori, Kuniaki Inoue, Tatsuo Yoneda, Tetsuya Tachiiri, Takahiro Nakai, Kenta Onishi, Yosuke Morizawa, Daisuke Gotoh, Yasushi Nakai, Makito Miyake, Nobumichi Tanaka, Kiyohide FujimotoABSTRACT
Introduction
Post‐transplant fractures are associated with increased mortality and reduced graft survival. Although computed tomography (CT)‐derived metrics, such as vertebral trabecular bone attenuation and abdominal aortic calcification have been reported as useful for assessing osteoporosis, their utility in predicting post‐transplant fractures in kidney transplant recipients (KTRs) has not been explored. This study examined pre‐transplant factors, including CT imaging parameters, associated with post‐transplant fractures using machine learning techniques.
Methods
This retrospective study included 111 primary living‐donor KTRs who underwent preoperative CT at our hospital between 2009 and 2023. Aorto‐iliac calcification was quantified using the Agatston score. Vertebral trabecular bone CT attenuation values (Hounsfield units [HU]) were recorded at T12 to L5 levels. Machine learning with SHapley Additive exPlanations (SHAP) was used to identify the top predictors of fracture.
Results
The median follow‐up period was 69 months. Twenty‐four recipients experienced fractures: hip ( n = 3), leg ( n = 6), arm ( n = 5), rib ( n = 3), and vertebrae ( n = 9). The L1 vertebral CT attenuation value and aortic segment calcification score emerged as the top predictors of fracture. Based on SHAP cutoffs (L1 CT = 104 HU; Agatston score = 504), recipients were categorized into Group 1: high L1/low calcification; Group 2: high L1/high calcification; and Group 3: low L1/high calcification. Compared to Group 1, fracture risk was higher in Group 2 (Subdistribution hazard ratio [SHR] 3.06; p = 0.034) and markedly higher in Group 3 (SHR 11.66; p < 0.0001).
Conclusion
Pre‐transplant lower vertebral trabecular bone attenuation and higher aortic calcification on CT are strongly associated with post‐transplant fractures.