DIFFERENCES IN MECHANICAL RESPONSE BETWEEN FRACTURED AND NON-FRACTURED SPINES UNDER HIGH-SPEED IMPACT

Objective. The differences in mechanical response between fractured an d non-fractured spines were investigated using a porcine spine impact model. Design. Ten three-vertebrae segments (C3-C5) of porcine spine w ere subjected to a single impact to study the trauma mechanism. Small steel balls glued to the vertebra and a highspeed camera were used to observe the deformation of vertebral body and disc during impact. Afte r trauma, the episodes of fractured specimens were compared with those of non-fractured specimens. Background. Experimental trauma models us ing 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 cl inical fractures can be produced. Methods. All of the specimens were s ubjected 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. Th e 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-dislo cation. All of these fractures were similar to clinical fractures. Com pared to non-fractured specimens, the fractured specimens had lower ma ximal force and longer reaction time. The characteristic steep decline in the middle region of the force-time curve was also consistently no ted in the fractured spines. Conclusions. Spinal fractures similar to those found clinically were successfully produced in porcine spines. T he characteristics of the mechanical responses observed should be help ful in the interpretation of events which occur during impact. Relevan ce Although this study used an animal trauma model, the results offer useful insight into fractures in humans. The exploration of the clinic al relevance of these results will be aided by their reproducible natu re and the well-controlled protocol used in the generation of the frac tures. (C) 1997 Elsevier Science Ltd. All rights reserved.