Isthmic Spondylolisthesis

Article written by John Czerwein MD, Alok Sharan MD, Terry Amaral MD, Vishal Sarwahi MD

Spondylolisthesis is slippage of one spine vertebrae on another. There are six different types of spondylolisthesis based upon the cause of the slippage.

The lower spine consists of five lumbar vertebrae and five sacral vertebrae that are fused together. The posterior portion of each lumbar vertebra consists of pedicles, laminae, spinous processes, and facet joints made up of superior and inferior articular processes. The vertebrae and sacrum are connected to each other via facet joints.. The superior processes face inward toward the spinal cord and the inferior processes face outward. This orientation allows for bending forward and backward of the spine. The region between the superior articular facet and lamina is called the pars interarticularis.

In isthmic spondylolisthesis, a defect is seen in the pars interarticularis; this allows for forward slippage of one vertebra on another. This defect occurs either through a congenital deformation or an acquired fracture . Fractures can develop as a result from repeated microtrauma of the pars as it is loaded in extension. Classic examples are a football lineman or gymnast as their respective sports require frequent hyperextension of the spine. The defect also appears to have a genetic component as one third of affected family members also have pars defects. Isthmic spondylolithesis most often occurs in the lower portion of the spine or the lumbosacral region, typically at L5-S1, or sometimes at L4-5.

Isthmic spondylolisthesis does not cause any symptoms., Symptoms can occur at any age but it is usually in the third or fourth decade of life. Symptoms related to isthmic spondylolisthesis usually consist of low back pain with associated tightness in the back of the legs. Patients often have a long history of periodic self-limited low back pain episodes that vary in intensity and/or duration. Because significant slippage is rare, patients seldom develop significant weakness in their legs.

Most patients with isthmic spondylolisthesis will respond to nonsurgical management. Treatment includes oral anti-inflammatory drugs for acute low back pain. Narcotic pain medication and muscle relaxants can also be used for acute pain but should be avoided for long-term treatment because of their addictive potential. Also, patients with acute back pain often benefit from physical therapy focused on strengthening abdominal and lower back muscles. Patients that have leg tingling/pain can benefit from selective nerve blocks or epidural steroid injections. Additionally, external bracing has been shown to benefit selected patients.

When patients fail conservative therapy (persistent pain, progression of leg pain/tingling, or progression of slip), surgical treatment is often indicated. The goal of surgical treatment is pain reduction, restoration of pre-symptomatic function, and prevention of further slippage. Possible operative procedures include: anterior interbody fusion, posterolateral fusion with and without instrumentation, combined anterior-posterior procedures, and posterior interbody techniques.

Though isthmic spondylolisthesis can cause significant back pain and discomfort, it has not shown to increase the risk of disability from low back pain. Treatment options are numerous and have been shown to be effective in controlling symptoms. Postoperatively, patients should get significant pain relief (particularly in their legs) and should eventually be able to return to a level of activity similar to before their symptoms began.