Differences in mechanical response between fractured and non-fractured spines under high-speed impact

OBJECTIVE: The differences in mechanical response between fractured and non-fractured spines were investigated using a porcine spine impact model. DESIGN: Ten three-vertebrae segments (C3-C5) of porcine spine were subjected to a single impact to study the trauma mechanism. Small steel balls glued to the vertebra and a high-speed camera were used to observe the deformation of vertebral body and disc during impact. After trauma, the episodes of fractured specimens were compared with those of non-fractured specimens. BACKGROUND: Experimental trauma models using the spines of mature animals have rarely been evaluated. Finding a well-controlled, reproducible protocol based on an easily accessible specimen was therefore important. These models will be promising if clinical fractures can be produced. METHODS: All of the specimens were subjected to high-speed flexion-compression loading. The impact to the load cell and the operation of the high-speed camera were synchronized. The force-time sequence and disc deformation curve were recorded. The results from fractured and non-fractured spines were then compared. RESULTS: There were three burst fractures, four pedicle fractures, one facet joint fracture, one compression fracture and one fracture-dislocation. All of these fractures were similar to clinical fractures. Compared to non-fractured specimens, the fractured specimens had lower maximal force and longer reaction time. The characteristic steep decline in the middle region of the force-time curve was also consistently noted in the fractured spines. CONCLUSIONS: Spinal fractures similar to those found clinically were successfully produced in porcine spines. The characteristics of the mechanical responses observed should be helpful in the interpretation of events which occur during impact.