| Objective:The purpose of this study was to investigate the effect of posture and prior loading history on the compressive strength. Methods:12 fresh human cadaver cervical spines were harvested and dissected into 24 motion segments containing two vertebra, intervening disc, ligament and joint capsular( C34 and C56).Compressive loads were applied so that the effects of two loading histories (hydrated , superhydrated) and two failure postures (neutral , flexed) could be examined. Dissection techniques and X-rays were used to document tissue damage. Results:Speciments had a lower ultimate compressive strength (27%-42%, P<0.001) when in a flexed posture than when in aneutral posture.When injured in a neutral posture,superhydrated specimens had a lower strength (29%,P<0.01) than dehydrated specimens. Conclusions:The spine may be more prone to injury early in the morning when the discs are at their greastest level of hydration and when they are in a fully flexed posture. |
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