Quantitative anthropometry of the subatlantal cervical longitudinal ligaments.

Study Design. The Quantitative anthropometry of the cervical longitudinal ligaments was determined in 20 human cadaveric subatlantal cervical spines at the limits of flexion and extension. Objectives. To provide measurements of cervical anterior and posterior longitudinal ligament lengths, widths, and cross-sectional areas at segmental levels. of Background Data. Although mathematical models of the cervical spine require specific data to predict kinematics, the anthropometry of the cervical spine has not been examined in detail. The dimensional changes of ligaments in physioiogic motion are not well characterized. Methods. Segmental lengths and widths of the cervical longitudinal ligaments were measured in sagittal plane flexion and extension, using a three-dimensional electromagnetic digitizer. The cross-sectional areas of the ligaments at resting length were measured with a laser micrometer system. Comparisons between anterior and posterior location and among segmental levels were made. Several ligaments were examined histologically to determine the insertion sites and, thus, to define the segmental length. Results. The anterior longitudinal ligaments were shorter in flexion than in extension. In extension, they were longer than the posterior longitudinal ligaments in flexion. The resting isolated ligaments were longer than the longest in situ lengths at several vertebral levels. The anterior longitudinal ligaments were wider at the disc than at the body. The cross-sectional area at C2-C3 was smaller than at subaxial levels. The longitudinal ligaments were observed to insert along the entire underlying vertebral body. Conclusions. The quantitative anthropometry of the cervical longitudinal ligaments is important in the development of accurate mathematical models of the cervical spine. The in situ ligaments may not be under tension in the physiologic range of motion.