Spondylolysis (spondy = spine, lysis = breaking) refers to an alteration in the morphology of the lumbar spine, involving an interruption in the continuity of the vertebral arch, more specifically the isthmus (pars interarticularis) between the superior articular process and the inferior articular process of the facet joint. This absence of the bone tissue then becomes filled with thick fibrous tissue. Whilst the causes of this condition are not fully understood, it is thought that some people may simply have a congenital weakness of the isthmus. Successive microtraumas, or a single sudden jolt may cause the bone to fracture at this point, resulting in subsequent back pain. If the isthmus is interrupted on both sides (as usually happens), the vertebral body tends to slide forward on the vertebra below, producing a spondylolisthesis (listhesis = sliding). This pathology is the main cause of back pain in adolescents and is frequently the culprit when younger athletes mention recurring back pain.

This most commonly affects the fifth lumbar vertebra (L5), which tends to slip on the body of the sacrum (S1) and also, although less commonly, the fourth lumbar vertebra (L4) sliding along the fifth (L5). This condition is typically benign, although it will progress over the years causing an instability in the lumbar spine. As such, it is important to control this situation as early as possible with proper clinical and diagnostic examinations. Medical history and clinical examinations may lead to a suspicion of this condition, but further, more specific investigation is required to reach a clear diagnosis. These tests include X-rays of the lumbar sacral spine to investigate the presence of any ‘sliding’ or fractures. However, these fractures can be difficult to see on X-rays, meaning more specialized CT scans are sometimes needed to rule out this possibility. MRI scans may provide evidence of a ‘stress response’ in the isthmus. In the most advanced cases, this sliding may result in stenosis (narrowing) of the spinal canal with subsequent nerve compression and irritative symptoms. It is important to remember that not all cases of spondylolisthesis are the result of a fracture isthmus, older adults may experience spondylolisthesis without any associated spondylolysis occurring as the result of advanced degeneration of the joint between the lumbar vertebra. 

Treatment here is almost always conservative, consisting of reinforcement exercises to reduce the sliding forward of the vertebral body, address the tilt of the pelvis, reduce lumbar lordosis and strengthen lumbar-pelvic control. In addition, physical and manual therapies can be used, depending on the severity of symptoms. Surgery should only be considered in cases of marked instability and a large ‘slip’, where fixation using surgical hardware may be necessary. Following surgery, many of the same issues will be present (poor lumbar-pelvic control) so a period of rehabilitation will still be required.