Isthmic Spondylolisthesis

Isthmic spondylolisthesis is a spinal condition in which one vertebra slips forward over the vertebra below (Figure 1). Although it most often occurs in the lower back (lumbar region), it may also occur in the cervical spine (neck region). Isthmic spondylolisthesis is associated with a defect or fracture of the pars interarticularis, the bone connecting the upper and lower facet joints (Figure 2).

Figure 1.

Vertebral slip at L5-S1*

Figure 2.

Fracture of the pars interarticularis

*Isthmic spondylolisthesis most often occurs at L5-S1, the fifth lumbar vertebra and first sacral segment.


Isthmic spondylolisthesis may be congenital (a person is born with a defect) or acquired (it develops due to the cumulative effects of spinal stress).

Congenital isthmic spondylolisthesis:

  • The facet joints and related bones do not form properly
  • Even if the condition is not present at birth, congenital defects may allow fracture with moderate stress later on

Acquired isthmic spondylolisthesis:

  • Heavy lifting, bending, twisting, or other stress cause small fractures which, in time, can lead to a vertebral slip
  • Weightlifters, football players, and gymnasts may suffer from this disorder because of spinal stress



Spondylolisthesis refers to the slippage of one vertebra over the one below it. The term isthmus refers to any connective structure, in this case, the slippage is a result of a defect of the pars interarticularis (which means “bridge between two joints”) associated with the facet joints. The degree of severity of isthmic spondylolisthesis is expressed as a percentage and then graded; there are five grades, with grade I least and grade V most severe.



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


Classification of Isthmic Spondylolisthesis

The Meyerding Grading System is used to classify the degree of vertebral slippage. This system is easy to understand. 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

Most cases of isthmic spondylolisthesis are Grade I or II. In general, the more severe the slip (Grades III and above), the more likely a surgical intervention will be required.



The physicians take many factors into account when recommending individualised state-of-the-art treatment, including the grade of the spondylolisthesis, pain levels, overall health, and personal preferences. Most cases of isthmic spondylolisthesis can be effectively treated without surgery. Treatments may include:

  • Short-term bed rest
  • Activity restriction
  • Over-the-counter or prescription pain medication
  • Anti-inflammatory medication
  • Muscle relaxants
  • Oral steroids
  • Steroid injections (i.e. epidural steroid injection)
  • Physical therapy
  • Bracing

Isthmic spondylolisthesis can be progressive, that is, it worsens with time. Patients treated by the hospital for isthmic spondylolisthesis should be monitored to measure their progress and adjust therapy, as needed.

Surgery may be recommended if isthmic spondylolisthesis:

  • Gets worse
  • Causes neurological problems
  • Is associated with chronic pain

The exact surgical intervention depends on the individual patient, but usually involves:

  • Instrumentation (such as rods, pins, screws, and so on)
  • Fusion (bone graft material)

In many cases, isthmic spondylolisthesis may be surgically treated using a minimally invasive approach, with small incision(s) and relatively rapid recovery times.



Isthmic sponylolisthesis is a serious condition that may cause pain, limit mobility, and decrease flexibility. Safe and effective treatments exist. A multimodal approach (using more than one type of therapy) may help certain patients make a full recovery. Most patients are able to experience significant relief when treated appropriately.


Risk Factors

In many cases, spondylolisthesis is congenital, that is, present at birth. Specific risk factors for congenital isthmic spondylolisthesis are not known. Acquired spondylolisthesis may be caused by excessive repetitive stress, such as might occur in a competitive athlete.



Isthmic spondylolisthesis is a serious condition but one that can be safely and effectively treated. Many patients are able to recover fully and enjoy healthy, pain-free, active lifestyles. There are many treatment options for isthmic spondylolisthesis but not all people are candidates for every treatment. The expert physicians can assist individuals who suspect isthmic spondylolisthesis in accurate diagnosis and can then provide advice as to the most advanced treatment options for an individual case.

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