The intent of this research is to develop a constitutive equation for the elastic fiber-dominant ligamentum nuchae and to determine the contributions of its two fibrous components to the parameters forming that constitutive equation. Tests specimens for the ligamentum nuchae were obtained from gross bovine specimens. Three types of mechanical tests were conducted on specially prepared test pieces. The first series of tests were stress relaxation tests at various strain levels, strain rates, and temperatures. The second series were loading and unloading cycles conducted at strain levels, strain rates, and temperatures comparable with those of the relaxation tests. The third test series were cyclic sinusoidally-varying strain tests conducted at various strain amplitudes. frequencies. and at temperatures just below and above the physiological range of the specimens considered. Tissue degradation and histologic analysis were employed to determine specifically the contribution of elastic and collagen fibers to the mechanical properties of the ligamentum nuchae as shown in the tests described.

A “quasi-linear" viscoelasticity law has been formulated based upon a suggestion forwarded by Y. C. Fung. Using this develOpment. certain material constants were determined from relaxation tests so as to establish a constitutive equation. The constitutive equation was then employed to predict the results of constant strain rate loading curves, hysteresis loops, and sinusoidal input tests.