Lumbar Discography: Study of Biomechanical Changes in the L1-L2 Intervertebral Disc of the Human Lumbar Spine Using Finite Element Methods

Lumbar discography is often used as a pain recognition technique for evaluating patients who have otherwise not responded well to non-surgical methods (radiology). While the injection technique provides unique information about the disc which is not obtainable through other methods, the procedure is suspected to cause prolonged damage to the disc. A study concentrating on equivalent stress in different regions of the disc shall provide useful insight on the prolonged effects of the lumbar discography procedure. A computational model of the functional spinal unit that accurately mimics its material properties and motion is required to simulate the medical procedure performed on the intervertebral disc. This study uses a hybrid finite element model of the L1-L2 motion segment of the lumbar spine of a 35-year-old male subject. In order to mimic spinal motion during flexion and extension, all supporting ligaments were added to the finite element model. Hyperelastic material properties were altered to simulate the discography procedure and equivalent von Misses stress values across the Annulus Fibrosus were recorded. A considerable increase in the equivalent stress across the annulus was observed in the punctured controls. Thus, the injection technique alters the stress concentrations across the disc and can have prolonged degenerative effects on the IVD.