Multi-Scale Structural and Tensile Mechanical Response of Annulus Fibrosus to Osmotic Loading

The annulus fibrosus (AF) is a multi-lamellar fibrocartilagenous ring in the intervertebral disc. The variation of biochemical composition from the outer to the inner AF is largely responsible for the heterogeneous mechanical properties. In vitro tissue-level studies require mechanical testing in aqueous buffers to avoid tissue dehydration. The varying glycosaminoglycan (GAG) contents from outer to inner AF suggest that the response to high and low PBS osmolarity may also be different with radial position. Previous studies in tendon and ligament have been conflicting: soaking tendon fascicles in PBS decreased tensile modulus¹ and treating ligament in buffer had no effect on modulus.²