Identification of elastic modulus of the porcine ligamentum flavum by tensile test

Abstract

In order to predict how much the human ligamentum flavum (LF) will be deformed during insertion of an epidural needle, the elastic modulus of a porcine LF was determined with a tensile test. LF specimens collected from porcine spines in a slaughterhouse were prepared into a rectangular shape with connecting vertebral bones. Preconditioning was repeated 20 times up to 0.1 MPa before the porcine LF specimens were tested. Strain rate was set at 0.03 and 0.5 s-1, in reference to previous studies. To calculate strain, we divided elongation length, measured with a laser distance sensor, by the initial length of each specimen. The stress-strain diagram exhibited a linear relation up to 30% strain. When tensile test stopped at 30% strain, force maintained a constant value without stress relaxation, which meant the specimen was exhibiting an elastic property only. Average Young's modulus was 0.13 ± 0.054 MPa (mean ± SD) for 0.03 s-1, and 0.14 ± 0.055 MPa (mean ± SD) for 0.5 s-1. Effect of strain rate was not statistically significant. Elastica-von-Gison stained image of the specimens revealed that they consisted of the LF and adipose, and that the average thickness of the porcine LF was thinner than that of specimens. Young's modulus of the porcine LF was estimated as 0.21 MPa in the thoracic and 0.19 MPa in the lumbar.

Keywords

• tensile test
• young's modulus
• ligamentum flavum
• strain rate