Transversely isotropic material characterization of the human anterior longitudinal ligament

• Use of a new ligament testing technique that facilitates material characterization using 10×10 mm2 samples.
• Nonlinear, anisotropic material parameters for the anterior longitudinal ligament.
• Comparison of reported results with previously reported spinal ligament material parameters.

The present work represents the first study to report transversely isotropic material parameters for the human anterior longitudinal ligament (ALL) in the thoraco-lumbar spine. Force-deformation data from multi-axial testing was collected from 30 cadaveric spine test specimens using an anisotropic quarter punch test technique. The experimental data was fit to a commonly used anisotropic soft tissue material model using an FEA system identification technique. The material model correlated well with the experimental response (R2≥0.98). The constitutive parameter values, as well as the nonlinear anisotropic stress–strain response of the ALL specimens are reported to facilitate application to biomechanical models (including finite element models) of the spine.

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