Geometric and mechanical properties of human cervical spine ligaments

This study characterized the geometry and mechanical properties of the cerv ical ligaments from C2-T1 levels. The lengths and cross-sectional areas of the anterior longitudinal ligament, posterior longitudinal ligament, joint capsules, ligamentum flavum, and interspinous ligament were determined from eight human cadavers using cryomicrotomy images. The geometry was defined based on spinal anatomy and its potential use in complex mathematical model s. The biomechanical force-deflection, stiffness, energy, stress, and strai n data were obtained from 25 cadavers using in situ axial tensile tests. Da ta were grouped into middle (C2-C5) and lower (C5-T1) cervical levels. Both the geometric length and area of cross section, and the biomechanical prop erties including the stiffness, stress, strain, energy, and Young's modulus , were presented for each of the five ligaments. In both groups, joint caps ules and ligamentum flavum exhibited the highest cross-sectional area (p <0 .005), while the longitudinal ligaments had the highest length measurements . Although not reaching statistical significance, for all ligaments, cross- sectional areas were higher in the C5-T1 than in the C2-C5 group; and lengt hs were higher in the C2-C5 than in the C5-T1 group with the exception of t he flavum (Table I in the main text). Force-deflection characteristics (plo ts) are provided for all ligaments in both groups. Failure strains were hig her for the ligaments of the posterior (interspinous ligament, joint capsul es, and ligamentum flavum) than the anterior complex (anterior and posterio r longitudinal ligaments) in both groups. In contrast, the failure stress a nd Young's modulus were higher for the anterior and posterior longitudinal ligaments compared to the ligaments of the posterior complex in the two gro ups. However, similar tendencies in the structural responses (stiffness, en ergy) were not found in both groups. Researchers attempting to incorporate these data into stress-analysis models can choose the specific parameter(s) based on the complexity of the model used to study the biomechanical behav ior of the human cervical spine.