Bioengineering Measurement.
Abstract
This report discusses the mechanism and modelling of vertebral injuries resulting from emergency egress from disabled aircraft. The Ewing hypothesis states that posterior structures of the spine act as motion limiters which favor the occurrence of the commonly observed anterior wedge fractures. This hypothesis was verified in human cadavers and it was shown that the fracture g-level could be increased considerably by moderately hyperextending the spine with a 5 cm thick wooden block placed behind L1. The existence of a second load path via the articular facets was demonstrated quantitatively and the role of abdominal pressure as a third load path was found to be feasible but not effective at high g-levels encountered during ejection. The effect of muscular response was studied using dogs subjected to low acceleration levels of 3 to 5g. Electromyography (EMG) was used to determine neuromuscular delay and the shape of the EMG derived muscle force-time curve. A two-dimensional mathematical model of the spine was validated against cadaveric data. The model was able to simulate spinal response reasonably well and predicted that the vertebral bodies in the lower thoracic region sustained the highest load during + G sub z acceleration. The mechanism of spinal injury is not one of simple compressive failure. The ability of the facets to act as a load bearing structure of the spine has important implications in the mechanism of vertebral body fracture. The restraint system can be used to change the proportion of load carried by the vertebral bodies and thus increase the g-level for fracture.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1977
- Accession Number
- ADA062464
Entities
People
- Albert I. King
Organizations
- Wayne State University