Spondylolysis is a term used to describe a defect that can develop in a bony portion of the spine. The defect is actually a stress fracture that occurs in a portion of the spine called the “pars”. Another term for spondylolysis is “pars fracture” or “pars defect”. This defect can lead to low back pain and in some cases, to instability of the bones.

Spondylolysis can cause the bone with the stress fracture to slip forward on top of the bone below. When this slip occurs, this condition is called isthmic spondylolisthesis. This is different than a slip caused by facet joint arthritis, a condition called “degenerative spondylolisthesis”.


The spinal canal is formed by a series of bony “arches” that form a tunnel when lined up. The “walls” of each arch are formed by columns of bone called pedicles. The “roof” of each arch is formed by a section of bone called the “lamina”. Each lamina attaches to the one below it through joints on each side called “facet joints”. The pars interarticularis is the portion of the bony arch that connects the facet joint of one level and the facet below. Biomechanically, this is the weakest part of the bony arch, and in some people a stress fracture can occur through the pars. This pars fracture is called “spondylolysis”.

Spondylolysis (Pars Fractures) and Lytic Spondylolisthesis

Causes of Spondylolysis

Pars fractures can occur from a sudden, traumatic injury, but more commonly these fractures occur gradually over a period of time as repetitive stress causes the weakened portion of bone to slowly fatigue and fracture. Although a stress fracture in the pars can develop at any age, it most commonly develops during childhood or adolescence and is present in six percent of people in this age group. This is because their spines are still developing, and the pars is the weakest part of the vertebra. Placing extra strain on this area of the spine during childhood increases the chance that a pars defect will occur. Spondylolysis mainly affects young athletes who participate in sports in which the spine is repeatedly bent backwards, such as gymnastics, football, and karate.

Spondylolysis (Pars Fractures) and Lytic SpondylolisthesisIsthmic Spondylolisthesis

Spondylolysis (pars defects) create a change in the biomechanics of the spinal segment qnthe bone above can begin to gradually slip forward on top of the bone below. This “slip” caused by the spondylolysis is called an isthmic spondylolisthesis. As it progresses, the disc between the bones is subjected to increased stress, leading to accelerated disc degeneration.


In the majority of cases, children and adolescents with pars defects do not experience symptoms, but in some cases spondylolysis can lead to lower back pain. For adolescents who do have low back pain, spondylolysis is the most common cause. In many cases spondylolysis goes undiagnosed until adulthood.

Patients with an isthmic spondylolisthesis (slip) tend to have more back pain due to the instability of the bones and the disc degeneration that occurs. In addition to back pain, radiating leg pain, numbness or weakness may occur as the nerve root behind the slipped vertebra becomes pinched.

  • Lower back pain with radiation into hips and buttocks
  • Radiculopathy – radiating leg pain or numbness caused by compression of the spinal nerves

Natural History –

What happens when the condition is not treated

  • Not all patients have symptoms
  • Symptoms may be short-lived and infrequent
  • Patients may develop more persistent and debilitating pain as the instability progresses

Three Phases of Treatment:

  • Phase I – Non-Invasive Treatments
  • Phase II – Spinal Injections
  • Phase III – Surgery

Goals of Each Phase:

  • Relieve Pain
  • Improve Function

Treatment Options: Phase I – Non-Invasive Treatments

  • Initial period of activity restriction and bracing for younger patients with spondylolysis without a slip (6 weeks)
  • Physical Therapy and Regular Home Exercise
    • Core and Back Strengthening
    • Flexibility and Stretching
  • Oral Medications
    • Steroids
    • Non-Steroid Anti-Inflammatories (NSAIDs)
    • Pain relievers
    • Muscle Relaxants
  • Ice and Heat

Treatment Options: Phase II –Steroid Injections placed into the Pars Defect

  • Done with x-ray guidance
  • May relieve symptoms, but will not repair the bone fracture
  • 1-3 injections may be needed

Treatment Options: Phase III – Surgery

Surgical Options for Lumbar Spondylolysis and Lytic SpondylolisthesisLumbar Fusion

    • When spinal instability (spondylolisthesis) is significant, fusion is necessary to fully relieve symptoms by restoring the proper spinal alignment and preventing further slippage
    • When instability is not present and leg pain is pre-dominant in <= Gr 1 Degenerative spondylolisthesis , only decompression is also enough.
    • Learn more about Lumbar Decompression
    • Learn more about Transforaminal Lumbar Interbody Fusion (TLIF)
    • Learn more about Minimally-Invasive Lumbar Fusion (MIS TLIF)

Emergency Medical Assistance