Effects of cervical spine posture on axial load bearing ability: a biomechanical study

Object. The authors conducted a study to assess the effects of cervical pos ture on the loadbearing ability of the cervical spine. Methods. Twelve cervical spine specimens obtained in 12 adult sheep were te sted. The specimens were randomly separated into two groups. In Group I the specimens were fixed in a lordotic posture, and in Group II they were fixe d in a straight posture. Axial compressive loads were applied at a constant rate of 5 cm/minute. Load-to-failure, time-to-failure, piston displacement at failure, and failure modes were recorded. Statistical analyses were per formed to detect differences between the groups. There was no significant difference in load-to-failure values between the t wo groups. However, the time-to-failure and the piston displacement values for the straight spines were significantly less than those for the lordotic spines. Additionally, the straight spines failed predominantly through ven tral elements, whereas the lordotic spines predominantly failed dorsally. Conclusions. It is concluded that a loss of a lordosis increases the risk o f injury to the cervical spine following axial loading.