Reference measurements for average human neurocranial bone density to inform head trauma interpretations

Abstract

ABSTRACT Bone density is one of many interacting variables that influence fracture initiation and propagation. Thus, average density values of the human neurocranium are an important consideration in skull trauma interpretation. However, neurocranial bone density has not previously been systematically evaluated. This study aimed to develop reference ranges for average neurocranial bone density and correlate this density with previously recorded average bone thickness. Using post-mortem computed tomography head scans of 604 deceased individuals, bone density (Hounsfield units) was measured at 20 locations across the neurocranium. Descriptive and inferential statistics were applied to establish bone density means; assess how age, sex and ancestry interact with density, and correlate density with thickness means . Mean density ranged from 78 Hu (mastoid process) to 1323 Hu (temporal squama); age, sex and ancestry significantly affected density, and a moderate negative correlation was found between density and thickness. Subsequently, reference measurements for density are presented here by age, sex and ancestry and are based upon a 95% confidence interval about the mean. These data provide a baseline for neurocranial density measurements that may be of use to forensic practitioners to assess if a cranium is of average (within the interval) or atypical (outside the interval) density.