Disc Herniation

The vertebrae of your spine are separated from one another by pads of cartilage called Intervertebral discs (IVDs). The discs cushion against the shocks and strains experienced as you move and put various stresses on your spine. The discs are subject to injury, disease, and degeneration with use over time. When the interior material of a disc called the nucleus pulopsus (NP) pushes out through a tear or weakening in the outer covering called the annulus fibrosus (AF), the disc is said to be herniated. There are 3 main types of disc injuries. The first disc injury consists of annular fiber tears which do not extend to the outer aspects of the disc. The inner NP does not completely leave the disc.  The second type of disc injury is a disc herniation.  A disc herniation consists of annular tears which run through the AF. The pressurized NP material can squeeze through the tears in the annulus and escape to the outside of the disc. When this occurs, the NP material may come in contact with nearby spinal nerves and even the spinal cord.  In the third type of disc injury, referred to as a disc bulge, the inner nucleus loses hydration; common in those with prolonged spinal stress and the elderly. This results in “bulging” of the disc. Similar to the previous injury, the nearby spinal nerves and spinal cord may become impinged from the bulging disc. Using mechanical testing experiments and analysis we are developing fracture and fatigue techniques for the AF of the IVD. Through this, the goal is to be able to predict crack propagation in the disc (annular tears) which ultimately leads to disc herniation.