The technical term for spinal instability caused by degeneration is spondylolisthesis, and the different types are discussed in the spondylolisthesis section. There can be spinal instability from trauma that causes injury to the spinal ligaments, discs and soft tissues or fractures of the spinal bones. In general, it takes a significant amount of force to cause trauma that would destabilize the spine; almost all of these patients are first evaluated in the Emergency Department.
Spondylolisthesis is a term used to describe instability and malalignment between two vertebral bodies and the disc in between them, usually in the lumbar or lower back region. These three parts, the disc and the spine bone above and below it, are often referred to as a motion segment and are named by the bone above and below, for example, L4-5. L4-5 is the most common level for degenerative spondylolisthesis. It means there is enough degeneration or arthritis at the L4-5 level that the L4 bone on top of the L5 bone is sliding off L5. Commonly, it will slide forward, called anterolisthesis, but it can slide to the side (laterally) or the back (retro). With degenerative spondylolisthesis, there is usually significant pinching or stenosis of the nerves at that level. With the instability from the sliding out of place of the bone and the nerve pinching, spondylolisthesis usually causes significant back pain, leg pain, and numbness. Isthmic spondylolisthesis usually occurs at L5-S1, the bottom disc in the spine. This happens when there is a stress fracture in part of the spine bone called the pars. The fracture commonly occurs in childhood and adolescence but can be years or decades before spondylolisthesis occurs. Once it happens, the symptoms are very similar to degenerative spondylolisthesis with components of back pain and leg symptoms.
Several symptoms drive the treatment of spondylolisthesis. Still, ultimately, definitive treatment involves stabilizing the bones so they do not continue to slide out of place and unpinching the nerves. This surgery is called a decompression and fusion, where laminectomy and foraminotomies are performed, and implants hold the two bones together, allowing the bone to grow between them, fusing them into one bone. Before symptoms are severe enough for surgery, physical therapy, medications and epidural steroid injections can be helpful to lessen the symptoms.