Does preliminary optimisation of an anatomically correct skull-brain model using simple simulants produce clinically realistic ballistic injury fracture patterns?

Abstract

Ballistic head injury remains a significant threat to military personnel. Studying such injuries requires a model that can be used with a military helmet. This paper describes further work on a skull-brain model using skulls made from three different polyurethane plastics and a series of skull 'fills' to simulate brain (3, 5, 7 and 10% gelatine by mass and PermaGel™). The models were subjected to ballistic impact from 7.62 × 39 mm mild steel core bullets. The first part of the work compares the different polyurethanes (mean bullet muzzle velocity of 708 m/s), and the second part compares the different fills (mean bullet muzzle velocity of 680 m/s). The impact events were filmed using high speed cameras. The resulting fracture patterns in the skulls were reviewed and scored by five clinicians experienced in assessing penetrating head injury. In over half of the models, one or more assessors felt aspects of the fracture pattern were close to real injury. Limitations of the model include the skull being manufactured in two parts and the lack of a realistic skin layer. Further work is ongoing to address these.

Keywords: 7.62 × 39 mm bullet; AK47; Assessment; Head; Military helmet.

Fig. 1

Sectioned 7.62 × 39 mm bullets. Left, Czech; right, Ukrainian

Fig. 2

Experimental setup. a Enfield proof mount. b Skull-brain model. c Camera and lighting setup. d Image capture on laptop PC

Fig. 3

Shot skull assessment setup. a Skull assessment stations. b Individual skull with score sheet

Fig. 4

Frontal impact sequence. a 0 ms. b 12.25 ms. c 16 ms. d 23.93 ms

Fig. 5

Examples of impacted skulls. The skulls have been reconstructed where possible. Fracture lines are highlighted using black ink. The skull numbers correspond to those in Appendix Table 7. a Skull 12, entry wound and associated fracture lines (i); skull 12, view from above. Fracture line and exit site (ii); skull 12, exit site, looking through to rear aspect of entry wound (iii). b Skull 26, entry site and associated fracture lines (i); skull 26, view from above (ii); skull 26, exit site, looking through towards rear aspect of entry wound (iii). c Skull 28, entry site (i); skull 28, exit site, looking through towards rear aspect of entry wound (ii)

Fig. 6

a Detail of entry wound (after DiMaio [18]). b Impact and passage of bullet through skull—front view (PFM). c Passage of bullet through skull—rear view—and development of secondary and tertiary fractures plus explosive comminution (PFM). d Detail of exit from cranial cavity (after Karger [22])