Mathematical analysis of fracture configuration in predicting outcome in complex anterior skull base trauma

Craniofacial trauma involving the anterior skull base produces a heterogenous injury with variance in fracture pattern, complexity and outcome. Variance is influenced by the biomechanical properties of the craniofacial construct and by the magnitude and vector of the impacting energy. Fractal dimension and other metrics applied to individual fracture patterns allows quantification of fracture complexity and severity, which can be used to correlate with neurological outcome. Frontobasal fractures from 81 patients admitted to two UK major trauma centres were analysed. Patients were divided into two groups: those with anteriorly-based vectors of impact and those with laterally-based vectors. Osseous disruption was quantified by: fractal dimension, fracture length, number of termini, and number of nodes, and then compared with neurological outcome using first recorded Glasgow Coma Score (GCS), and requirement for intubation. As fracture length increased, fractures from anterior impacts became more complex and reticulated compared with lateral impacts; fractal dimension also increased more rapidly for anterior impacts. Longer fracture length in both groups was associated with a significantly lower GCS, and increased requirement for intubation (p < 0.001 and p < 0.001 respectively). Fracture propagation and severity of head injury was different in anterior-directed trauma compared to lateral-directed trauma. Consequently, we suggest that the central region of the anterior skull base acts to primarily absorb impact force thereby behaving as a protective ' crumple zone ' . In severe mechanisms the protective mechanism is exceeded and the fracture length tended to that of the lateral group worsening prognosis.