Young's modulus measurement of the porcine ligamentum flavum for evaluating the deformation during epidural insertion

In order to check validity of the porcine ligamentum flavum as a substitute of human tissue for evaluating the epidural needles, the thickness and the Young's modulus were measured, and a finite element analysis was carried out. Twenty-four specimens were stained by the Elastica-van Gieson method. The average value of the thickness was 1.2 mm. The tensile tester was employed for measuring the Young's modulus. A cross sectional area was obtained by X-ray CT image. Young's modulus was 1.6 MPa. The measured properties of a porcine ligamentum flavum showed a reduced thickness and smaller Young's modulus than the human ligamentum flavum. On a finite element analysis, the shape of the ligamentum flavum was modeled as a square plate 5 mm in width and 5 mm in depth. The thickness and the Young's modulus were set at the measured value for a porcine model, and value from the literature for a human model. For simplicity, a constant load of 10 N was applied at the center of each model. The porcine model exhibited deformation 1.7 times that of the human model.