Spondylolysis/Spondylolisthesis

By Edward S. Pratt, M.D., M.B.A.

Spondylolysis is thought to represent a small stress fracture that develops in the low back of children after minor trauma. The break occurs in an area of the spine called the “pars intrarticularis” or “part between the joints”. This condition occurs in less than 5% of the population, however in certain football players, cheerleaders and gymnasts the incidence can be as high as 50%. When symptomatic it causes low back pain (which is made worse with back bending), and stiffness in the hamstrings caused by walking in a habitual forward bent, knee flexed posture. Treatment consists of stabilization and stretching exercises while avoiding activities that cause pain. Occasionally, more aggressive techniques including pain blocks or surgical fusion are required, however these are seldom necessary.

When spondylolysis occurs on both sides of the spine it can lead to a slipping of one vertebra on another, a condition known as spondylolisthesis (spine slip). The vertebrae will usually only slip a centimeter or so, but occasionally slippage can be extreme. The best prognosticator for slip progression here seems to be the angle the slipping bone has with the pelvis (slip angle). The more vertical the slip angle, the more likely the slip will get worse over time. The treatment of spondylolisthesis is similar to spondylolysis in milder forms, but can require surgical spine fusion in more severe cases. Spondylolistheses that is progressing on repeated X-ray exams or have slipped more than 50% of the way off of the vertebrae below are candidates for fusion. Spine fusion for spondylolisthesis as with scoliosis is designed to lay down bone graft between the two slipping vertebrae so that they may form a solid sheet of bone between them, thus preventing further slip. As with scoliosis this is occasionally done with rods and screws, but in children it is often done without instrumentation. As we will see later, adult cases are very different. The rates for solid fusion and pain relief are superior when rods and pedicle screws are used as part of the fusion process.