Microstructure of the anterior iliac Spine: Identification of trends and relation to fracture tolerance

Seatbelt-induced pelvic iliac wing injuries have been observed since the 1970s, but only recently has there been quantification of fracture tolerance and injury risk of the iliac wing. Previous studies have shown a wide variation in iliac wing fracture tolerance with no significant relationships to pelvis size, sex, or other factors. A weighted average bone density (BD) calculation of the entire iliac wing produced the best predictive performance of fracture tolerance in parametric (Weibull) survival models. As a result, we endeavored to evaluate local bone microstructural properties at the site of loading and evaluate their relationship to fracture tolerance. Anterior iliac spine samples (ASIS, AIIS) were extracted from 42 iliac wings, originating from 11 male and 10 female post-mortem human surrogates (PMHS). Samples were scanned using micro-computed tomography, then 20 different cortical and trabecular bone measurements for each sample were evaluated. A principal component analysis (PCA) was conducted to reduce the dimensionality and identify the features of iliac wing microstructure that account for the most variation in the measurements. The first principal component, which represented bone quantity, accounted for over 33 % of the variation in the specimen microstructures. This component improved the survival model fit to the data more than any other previous model. Results suggest that bone quantity may explain much of the variation in iliac wing fracture tolerance.