Effects of age, gender, spinal level and loading conditions on spinal injury risk in children

Dr Elizabeth Clarke (PhD)1, A/Prof Lynne Bilston (PhD) 1, Dr Julie Brown (PhD) 1, Dr Richard Appleyard (PhD)2, Dr Cathy Gorrie (PhD)3

1Prince of Wales Medical Research Institute, Barker St, Randwick, NSW 2031
2Murray Maxwell Biomechanics Laboratory, Level 10, Kolling Building, Royal North Shore Hospital, St Leonards, NSW, 2065
3The University of New South Wales, Randwick, NSW, 2031

This research group has been investigating the mechanisms of paediatric spinal injury in motor vehicle accidents (MVAs) for many years. Based on findings that a low risk of injury to children who were correctly using an appropriate child restraint system, legislative changes and education campaigns are being implemented that will work to reduce spinal injury in children. However, there are additional factors beyond restraint status that may affect spinal injury risk in children. A/Prof Bilstons group recently completed detailed reviews of incidence and mechanisms of child spinal injuries in Australia. These studies identified child motor vehicle occupants as the highest priority group, and that (regardless of restraint status) child age, gender and the crash type, are major predictors of spinal injury. Furthermore, the proportions of injury to different spinal levels changed with age and injury mechanism. The team has also observed age effects on spinal injury severity and level of involvement, and an over-representation of girls among spinal injured children in traffic accidents. The groups recent laboratory work has suggested equivalent impact severity produces more severe damage to the younger spinal cord, and has identified differences in spinal level biomechanical properties with age. In addition to differences in exposure from different restraint types, these studies strongly suggest there may be inherent differences in injury response due the maturity of the spinal column that likely persists through to adolescence.

Spinal specimens: axial CT scans through the mid-thoracic vertebrae of adult (left), juvenile (middle) and infant (right) pigs.

Over the next 2 years this research team will undertake a collaborative, multi-institution study funded by SpineCare Australia, to investigate the effect of impact speed on spinal cord injury severity, and the effect of gender and developmental age on failure properties of the cervical, thoracic and lumbar spine. These studies will involve: (1) epidemiological investigations using the US NASS database to identify relationships between age, gender and crash type on spinal injury severity in children; (2) laboratory-based models of spinal cord injury to investigate the relationship between impact conditions and severity of damage to the neonatal spinal cord; and (3) studies using a custom spinal testing apparatus to determine biomechanical properties of the male and female developing spine at each spinal level.
It is hoped that the outcomes from this extensive research program will aid in developing better physical models (such as crash test dummies) to test safety devices for children in MVAs. The study may also identify behaviour modification strategies, or certain groups of children to target for specific spinal injury prevention measures. Finally, this information will help identify minimum performance requirements for vehicle safety systems in order to prevent serious spinal injuries in children.