Automated determination of bone age and bone health index in pediatric liver transplant recipients

Background: Bone metabolism in children who have undergone pediatric liver transplantation (pLT) can be negatively affected, particularly in the presence of cholestasis. Pediatric bone status is a critical determinant of bone health through adulthood. The aim of this study was to evaluate bone age (BA), a marker of skeletal maturity, and bone health index (BHI), a surrogate marker of bone density, in pLT recipients. Methods: A total of 449 left hand radiographs of 207 patients [median age at LT: 1.1 years (IQR: 0.43; 6.8 years); female = 50.2%], all entered in the local pLT register, were evaluated in this retrospective, IRB-approved single-center exploratory study. Fully automated determination of BA-standard deviation score (BA SDS) and BHI SDS was performed using a commercial, CE-marked AI tool and relationships with age, sex, underlying disease (biliary atresia vs. non-biliary atresia), height percentile and plasma parathyroid hormone (PTH) were assessed using t-tests, permutation tests, and Pearson correlation in both the whole cohort and the subgroup with biliary complications. Results: Mean BA SDS pre-LT was 0.03 ± 1.50, 0.03 ± 1.70 at year 1, -0.07 ± 1.62 at year 3 and − 0.21 ± 1.63 at year 5. Mean BHI SDS pre-LT was − 1.8 ± 1.20, -1.6 ± 1.20 at year 1, -2.0 ± 1.10 year 3 and − 2.2 ± 1.3 at year 5. A significant positive correlation was observed between BA SDS and height percentiles at all timepoints. PTH showed a significant inverse correlation with BA SDS at years 3 and 5 and with BHI SDS at year 5. No significant differences in mean BA SDS or BHI SDS were observed between groups with or without biliary complications or PTCD/ERCP at any timepoint. Conclusions: While mean BA SDS remained stable around zero post-LT, mean BHI SDS was consistently reduced and declined progressively until year 5, indicating decreased bone mineral density. Further prospective studies with larger cohorts are needed to determine the utility of automated BA and BHI assessment following pLT.