Spine Fractures in Open Cockpit Open Wheel Race Car Drivers 2006-01-3630

Spinal fractures in open cockpit open wheeled racecars have increased in frequency over the past 10 years (7.5% of all racing injuries in 1995 to 18.7% currently). In order to quantitate this and investigate potential causes we collected all fractures occurring in 5 open wheeled series from 1996 to 2005. The ultimate goal of the study is to identify causative factors that can be altered to lessen the fracture risk. This is a multipart study. These fractures were categorized as to fracture type and severity, and correlated to ADR-2 data from the race car. Also used in the analysis were data from a rearward impact barrier test, HYGE sled testing and development of a computer model. (Development of the model is reported in a separate submission) 38 incidents resulted in fractures in 36 different drivers (2 involved in 2 incidents). 54 spinal levels were injured with 9 drivers sustaining injury at more than one level. The thoracic and thoracolumbar spine was involved most frequently. Of the 38 injured drivers 26 sustained injury in a rearward directed impact 15 of which produced thoracic or thoracolumbar fractures.

Fractures were classified according to Gertzbein's Comprehensive Classification System. All thoracic and thoracolumbar fractures sustained in rearward impacts were Type A axial compression fractures. We created a Fracture Severity Index to allow for analysis of the severity of these fractures which were similar in morphology. Fractures sustained in rearward impacts were less severe than fractures in frontal impacts. Rearward impacts accounted for 67% of the injuries, 63% of the levels injured and averaged 2.9 severity index (max 6.0).

Rearward impact was investigated with a barrier test of a fully loaded Indy Car at an impact speed of 80kph. Occupant kinematics observed documented the ramping phenomena as well as a potential source of the vertical loading.

Injured drivers ADR2 data was trended with fracture level, type, and severity.

The ADR-2 is an Accident Data Recorder that is supplied by Delphi. It is secured to the chassis of the race car and is required equipment in the IRL and IPS as well as the other series included in this report. It senses and records key vehicle parameters at 1000 samples per second prior to, during and after a pre determined triggering event. Some of the parameters recorded include X,Y,Z axis accelerations, yaw rate, steering angle, throttle position, and wheel speed.

Sled test using a 60g pulse (Indy Car pulse) and THOR ATD were carried out to verify and validate data from the ADR-2.

Thoracic and thoracolumbar spine fractures are characterized by compressive loads; the ADR-2 data demonstrates vertical axis spikes which are reproducible on the sled in the T8 and T12 load cells.

These data and literature review identified threshold loads predictive of spinal fracture in an open cockpit open wheeled race car.

Continued investigation is focused on making alterations in the seat contour and foam material to help mitigate the impact loads, reducing the ramping phenomena and therefore compression loading on the spine.