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Cervical Facet Joint Mechanics: Its Application to Whiplash Injury
Technical Paper
99SC15
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Language:
English
Abstract
Epidemiological and clinical studies have identified the
cervical facet capsule as a potential site of whiplash injury and
prerotation of the head and neck as a risk factor for whiplash
injury. However, biomechanical data related to the cervical facet
capsule and its role in whiplash injury remain limited in the
literature. In this study, cervical spine motion segments were
tested in a pure moment test frame and the full field strains were
determined throughout the facet capsule. Motion segments were
tested with and without a pretorque in pure bending. Bending tests
were followed by isolated facet elongation tests to failure.
Maximum principal strains during bending were compared to failure
strains.
Statistically significant increases in principal capsular
strains were observed in the facet which was contralateral to the
pretorque. In contrast, no significant differences were present in
the ipsilateral facet when large flexion-extension moments were
applied. Capsular strains during bending were significantly less
than strains at catastrophic joint failure. The same was true for
subcatastrophic failures, except in the presence of a contralateral
pretorque. The results of this study indicate that pretorque of the
head and neck increases facet capsular strains, supporting the role
of this joint in the whiplash injury mechanism. The facet capsule
does not appear to be at risk for gross injury during pure bending
through an angular range of motion similar to the range of motion
experienced in experimental studies of whiplash. However, the
findings of this study indicate that a small portion of the
population may be at risk for subcatastrophic injury when exposed
to these loads.