The purpose of this study is to investigate the biomechanical properties of the anterior longitudinal ligament (ALL) and the posterior longitudinal ligament (PLL) of the human cervical spine. Twenty C 3-C 4 and twenty C 5-C 6 motion segments are dissected from the spines of human cadavers. Experimental specimens of the bone-ligament-bone complex are prepared for mounting on a testing jig. Static tensile tests are performed with an Instron-type material test system. Dynamic biomechanical properties were tested with a biomechanical spectrometer.
The failure load and failure stress of the PLL tend to be higher than those of the ALL, but there are no statistically significant differences between them. The tan 6 of the ALL is higher than that of the PLL (p<0.01). The dynamic stiffness of the PLL is higher than that of the ALL (p<0.01), but there was no statistically significant difference in the dynamic elastic modulus between the ALL and the PLL.
These results imply that the PLL has better biomechanical properties as a stabilizer for cervical motion than the ALL in the lower cervical spine.