Spondylolisthesis occurs when one vertebral body slips forward over the one beneath it.  Isthmic spondylolisthesis is one type.  Isthmic refers to the tube-shaped bone called the pars interarticularis, or simply the pars.  Each of your spine’s joints (facet joints) contains pars.  The pars connect the upper and lower facet joints and help stabilize the joint.  Isthmic spondylolisthesis happens when the pars breaks.  Spondylolisthesis is more common in the lumbar spine (low back).


The pars defect may be congenital (at birth), result from improper bone formation, or become damaged or broken by the accumulative effects of spinal stress.  Repeated heavy lifting, stooping over, or twisting may cause small fractures to occur and lead to a vertebral slip.  Weightlifters, football players, and gymnasts may suffer from this disorder because of considerable spinal stress.


Although isthmic spondylolisthesis can cause spinal instability, not all patients experience pain. Typical symptoms include:

  • Back pain (low back or neck)
  • Sciatica
  • Muscle spasms
  • Leg, arm weakness
  • Tight hamstring muscles (legs)
  • Irregular gait or limp
  • Bowel or bladder dysfunction (rare)

Accurate diagnosis

Vertebral slip associated with isthmic spondylolisthesis can progress and worsen.  Consult an expert about your back pain with or without extremity pain, pre-existing or changing spinal disorder.  An accurate diagnosis is essential to an effective and successful treatment plan.

Your medical history and physical and neurological examinations are very important.  You and your doctor discuss your symptoms, when they started and treatments tried.  The doctor tests your reflexes and evaluates you for muscle weakness, loss of feeling, and signs of neurological injury.

Diagnostic testing helps the doctor confirm your diagnosis.  A simple spinal x-ray can show a spondylolisthesis.  Typically, several x-rays are taken: side (lateral), standing (front and back), bending forward (flexion) and bending backward (extension).  The flexion/extension studies help your spine specialist to evaluate your range of motion and spinal stability.

Other diagnostic imaging studies may include a CT or MRI series.  A MRI study is of particular use to assess nerve and/or spinal canal (cord) compression.  Your doctor will explain the purpose of these and other tests.

Classifying Isthmic Spondylolisthesis

The Meyerding Grading System is used to determine the degree or severity of the vertebral slip.  All of your imaging studies, including information from your medical file, are considered in the assessment of your spondylolisthesis and its characteristics.

Meyerding Grading System

  • Grade I:  1-24%
  • Grade II: 25-49%
  • Grade III: 50-74%
  • Grade IV: 75%-99% slip
  • Grade V: Complete slip (100%, spondyloptosis)

Most cases of isthmic spondylolisthesis are Grade I or II. Grades III and above are more severe and may require surgical treatment.

Treatment options

Many isthmic spondylolisthesis cases are treated without surgery.  Your doctor may combine more than one therapy to maximize the success of your treatment plan.

Isthmic spondylolisthesis can be progressive.  This means the spondylolisthesis worsens with time. This is why it is important to follow up with your doctor to monitor your treatment progress and spondylolisthesis.

When your surgeon may discuss surgical treatment

  • Spinal instability (slip progression)
  • Bowel or bladder dysfunction
  • Neurologic dysfunction
  • Unrelenting pain, symptoms
  • Non-operative treatment fails

Surgical treatment

Surgical treatment of isthmic spondylolisthesis aims to reduce (decompress) nerve compression and stabilize the spine (stop the slip).  You may be a candidate for a minimally invasive spine surgical procedure to alleviate neurological dysfunction.  Spinal stabilization and fusion stops the slip, movement, and holds the spine stable as you heal.


Many patients fully recover and enjoy healthy, pain-free, and active lives.  We hope this information about isthmic spondylolisthesis has answered your immediate questions.  Remember, your doctor is your most valuable source to answer your questions about symptoms and your healthcare.

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