In vitro biomechanical study of female geriatric cervical vertebral bodies.

Compressive strength tests were conducted on fresh human geriatric female cervical vertebral bodies. Nineteen specimens were compressed to 50% of their initial height using an electrohydraulic testing device. The mechanical force-deflection response was sigmoidal with continuously changing resistance. The mean cross-sectional area and bone mineral content (BMC) of the vertebral bodies progressively increased from C3 (area: 333.8 mm2, BMC: 1.56 g) to C6 (area: 499.7 mm2, BMC: 2.18 g). The maximum compressive force increased from 1060 N at C3 to 1787 N at C6. The stiffness and the energy absorbed at failure also increased from C3 to C6 (stiffness: 279.95 to 556.41 N mm-1, energy: 2.45 to 4.16 J). These parameters demonstrated a decreasing tendency from C6 to C7. The relatively higher biomechanical parameters at the sixth vertebral level compared with its caudad and cephalad counterparts may be due to the fact the transition of the cervical lordosis to thoracic kyphosis begins at this level. Furthermore, the change in the anatomy of the unicinate processes in the cervical column around this region may also be a contributing factor.