Isthmic Spondylolisthesis

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Isthmic spondylolisthesis is a spinal condition where one vertebra slips forward over the vertebra below. It’s caused by a defect, or fracture, of the pars interarticularis, a bone that connects the upper and lower facet joints. You may inherit the defect or obtain a fracture by the accumulative affects of spinal stress. Sometimes isthmic spondylolisthesis affects young athletes.

Symptoms of Isthmic Spondylolisthesis 

Although isthmic spondylolisthesis can cause spinal instability, not all patients find the condition painful. Symptoms of isthmic spondylolisthesis may include:

  • Low back pain
  • Sciatica
  • Muscle spasms
  • Leg weakness
  • Tight hamstring muscles
  • Irregular gait or limp 

Causes of Isthmic Spondylolisthesis 

Isthmic spondylolisthesis may result from failure of bone to form properly. Accumulated physical stress to the spine may cause weak or insufficiently formed vertebral structures to break. Repeated heavy lifting, stooping over or twisting may also 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.

Diagnosis & Treatment at UVA Health

Your doctor will ask your medical history and perform a physical exam. Your doctor may also order diagnostic tests that include:

  • X-rays
  • CT scans
  • MRI scans

Classification of Isthmic Spondylolisthesis 

At UVA Health, we use the Meyerding Grading System to classify the degree of vertebral slippage. Slips are graded on the basis of the percentage that one vertebral body has slipped forward over the vertebral body below. 

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

Your doctor considers the degree of slip and factors, such as intractable pain and neurological symptoms, when deciding on the most suitable treatment. Most cases of isthmic spondylolisthesis are Grade I or II. As a general guideline, the more severe slips (Grades III and above) are most likely to require surgical intervention.

Nonoperative Treatment 

Most cases of isthmic spondylolisthesis are treated without surgery.

Isthmic spondylolisthesis can be progressive and worsen with time.


You may require surgery if your isthmic spondylolisthesis progresses or causes neurologic problems, such as incontinence. Spinal instrumentation (i.e., rods, screws) and fusion (bone graft) are common procedures to stop slip progression and stabilize the spine.