Role of mechanical representativity in multiaxial and transverse mechanics of human annulus fibrosus: A microstructure-based biphasic finite element study.

The annulus fibrosus (AF) of the intervertebral disc is composed of a hierarchically organized network of micro-sized oriented collagen fibers (OCF) and nano-sized elastic fibers (NEF) embedded within a fluid-saturated matrix. Interlamellar (ILM) zones provide cohesion between adjacent AF lamellae (LM) and the OCF network. This complex microstructure varies depending on the disc region, thereby affecting both multiaxial and transverse AF mechanics.