The biomechanical properties of porcine intervertebral disc tissue treated with different fixation solutions

Human cadavers used for teaching are often preserved through arterial embalming. The intervertebral disc is naturally avascular, therefore it is unknown if the fixative reaches the disc and alters its biomechanical properties. The current study compared annulus fibrosus biomechanics from porcine discs treated with commonly used fixation solutions. Porcine cervical spines were submerged for 14 days in one of the following fixation solutions; Control (no fixation); Ethanol; Imperial College London; Saturated Salt Solution, and Surgical Reality Fluid. Post submersion, discs were excised and subjected to four annular tests. Fixation altered the mechanical properties of the annulus with certain solutions having a greater impact. The saturated salt solution had the greatest effect on annular mechanical properties; specifically, a significantly lower toe region strain and higher stress at 15 % strain when compared to the unfixed controls was observed. Additionally, the saturated salt solution also significantly reduced annular adhesion peel stiffness, strength, and adhesion variability. Surgical Reality Fluid also reduced toe region strain and increased stress at 15 % strain when compared to unfixed controls, but to a lesser extent and did not appear to affect adhesive mechanical properties. Ethanol fixation significantly lowered stress at 15 % strain but did not appear to affect any other mechanical variable. Last, the Imperial College London solution did not show significant alterations to any annular property measured. Fixation alters mechanical properties of the annulus fibrosus with varying degrees depending on the solution used. This study helps provide guidance when using fixed tissue for biomechanical annulus testing.