Novel Lap Test Determines the Mechanics of Delamination Between Annular Lamellae of the Intervertebral Disc

This study introduced a novel lap-test methodology to quantify the mechanical properties governing delamination between adjacent annular lamellae of the intervertebral disc. Bilayer annulus fibrosus specimens harvested from porcine cervical discs were subjected to uniaxial tensile loading while tracking inter-lamellar displacement and force response. Results showed that shear stresses at the inter-lamellar interface are highly localized near the ends of the bonded region, with peak loads occurring prior to sudden interface weakening and sliding. Despite interfacial failure, specimens retained substantial load-bearing capacity over large displacements. These findings provide new insight into the mechanics of annular delamination and the initiation of disc herniation.