Geometric and Mechanical Properties of Human Cervical Spine Ligaments

Abstract

This study characterized the geometry and mechanical properties of the cervical 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 models. The biomechanical force-deflection, stiffness, energy, stress, and strain data were obtained from 25 cadavers using in situ axial tensile tests. Data were grouped into middle (C2-C5) and lower (C5-T1) cervical levels. Both the geometric length and area of cross section, and the biomechanical properties including the stiffness, stress, strain, energy, and Young's modulus, were presented for each of the five ligaments. In both groups, joint capsules 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 lengths were higher in the C2-C5 than in the C5-T1 group with the exception of the flavum (Table 1 in the main text). Force-deflection characteristics (plots) are provided for all ligaments in both groups. Failure strains were higher for the ligaments of the posterior (interspinous ligament, joint capsules, and ligamentum flavum) than the anterior complex (anterior and posterior longitudinal ligaments) in both groups. In contrast, the failure stress and Young's modulus were higher for the anterior and posterior longitudinal ligaments compared to the ligaments of the posterior complex in the two groups. However, similar tendencies in the structural responses (stiffness, energy) 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 behavior of the human cervical spine.

Strain rate dependent properties of younger human cervical spine ligaments

“…Ten previous studies have been conducted on cervical spine ligament material properties to failure under tensile loads; four at quasi-static strain rates Pintar, 1986;Chazal et al, 1985;Przybylski et al, 1996;Yoganandan et al, 1998;Yoganandan et al, 2000), three at high strain rates (Ivancic et al, 2007;Bass et al, 2007;Shim et al, 2005), one at both quasi-static and high rates and two conducted solely on craniovertebral ligaments . It should be noted that in two cases, results were published from the same study in different articles; Yoganandan et al (1998Yoganandan et al ( , 2000 published two articles, and Myklebust et al (1988) published results from Pintar's PhD thesis (1986).…”

“…It should be noted that in two cases, results were published from the same study in different articles; Yoganandan et al (1998Yoganandan et al ( , 2000 published two articles, and Myklebust et al (1988) published results from Pintar's PhD thesis (1986). Average cadaver ages used in the studies had a wide range from the youngest of 49 (37 to 53) years old (only craniovertebral ligaments were tested; , to the oldest of 81 (71 to 92) years old (Ivancic et al, 2007).…”

“…A number of studies have been conducted on isolated cervical spine ligaments to identify tensile behaviours ranging from quasi-static strain rates Chazal et al, 1985;Przybylski et al, 1996;Yoganandan et al, 1998;Yoganandan et al, 2000) to high strain rates Ivancic et al, 2007;Bass et al, 2007;Shim et al, 2005). This data has provided an excellent background on cervical spine ligament behavior.…”

“…Yoganandan et al (1998Yoganandan et al ( , 2000 evaluated the effect of spinal level but the results were limited to two regions (middle and lower), rather than individual level effects. Numerical models have shown that under loading cases, the distractions and forces seen at each spinal level vary (Stemper et al, 2006), and this suggests the importance that ligaments at each spinal level are modeled accurately.…”

Posterior cervical fixation following laminectomy: a stress analysis of three techniques

“…The endplates were considered to be part of the Six different ligaments approximating the ligamentous structures in the cervical spine were incorporated into the FE model as tension-only nonlinear connector: anterior and posterior longitudinal ligaments, interspinous ligament, spinous ligaments, ligamentum flavum, and capsular ligaments. Their insertion points were chosen to mimic anatomic observations as closely as possible [16,17]. Material and mechanical properties shown in Table 1 for each spinal component represented the most commonly used values obtained from the literature [18][19][20][21].…”