New PMCT multi-indicator ossification standards for age estimation of the knee in modern Australian and North...

Skeletal age estimation is crucial to medicolegal work, aiding subadult identification, and living age assessments in legal contexts. This study aims to document the ontogeny of knee skeletal indicators on post-mortem computed tomography (PMCT), and quantify interpopulation variation between modern American and Australian children. PMCT data from 402 Australian subadults from Victoria, Australia (228 males, 174 females), and 445 North American subadults from New Mexico (233 males, 202 females) were retrospectively accessed. Thin-slice data were visualized as multiplanar reconstructions, and an ordinal scoring system applied to 11 indicators on the femur, tibia, and fibula. High repeatability was exhibited by excellent intra-rater (ICC = 0.99) and good inter-rater (ICC = 0.89) agreement. Transition analysis produced maximum likelihood maturation estimates, with age parameters derived from a multivariable Bayesian model using 68-95% credible intervals. Active knee fusion occurred in Australian females aged 10-16 and males 12-18, with complete fusion of all sites no earlier than 14 and 16 years. North American females showed slightly later fusion (11-15 years), consistent with males (11-16 years). Sexual dimorphism was consistent in both subpopulations, and interpopulation differences were especially prominent in later adolescence to early adulthood for the epiphyses for males, but were not identified for most morphological indicators. Recalibrated, normative PMCT knee development standards are presented for Australian and North American subadults, identifying four indicators especially informative for age estimation across developmental profiles derived from a Bayesian cluster model. Our findings support use of population-specific standards, particularly in later fusion stages after 15-16 years, to improve accuracy in forensic and clinical applications.