Diagnosing Spondylolisthesis

Spondylolisthesis is a misalignment of the spine that occurs when a vertebra, one of the bones that make up the spine, slips forward. Doctors at NYU Langone’s Spine Center and the Endoscopic Spine Surgery Program use sophisticated imaging tools to identify the location and extent of a slipped vertebra and confirm whether there is damage to the surrounding bones or nerves.

Causes and Symptoms of Spondylolisthesis

Spondylolisthesis usually affects a vertebra in the lower spine, called the lumbar spine, and may occur at any age. In children and adolescents, the condition is often the result of stress fractures in the small bones, called the pars interarticularis, that connect the vertebra to the spine’s joints and keep the vertebrae in place. This condition, called spondylolysis, may be present at birth or may develop as a result of an injury.

In adults, spondylolisthesis usually occurs in people over age 40 as the result of age-related degeneration in the spine’s joints and discs, such as osteoarthritis of the spine or degenerative disc disease. These conditions may lead to changes in the alignment of the spine, putting additional pressure on the pars interarticularis and preventing them from keeping the vertebrae in position.

Because these conditions tend to cause degeneration in more than one vertebra, people who have them may experience spondylolisthesis in more than one place in the spine. If multiple vertebrae slip forward, the lower spine may develop an unusual inward curve, called lordosis, or the middle spine an unusual forward curve, called kyphosis.

A traumatic injury, such as a car accident, can cause spondylolisthesis in people of any age. Some conditions, such as osteoporosis or osteogenesis imperfecta, in which a person has weak bones that break easily, may increase the risk of a fractured vertebra and spondylolisthesis.

Symptoms vary according to how much the vertebra has moved and whether the displaced bone pinches any of the nearby nerves that exit the spinal column through spaces in the vertebrae. Some people may not experience any symptoms if the bone has only slightly moved out of place. If the bone’s movement is more severe, a person may experience chronic, aching pain in the lower back that worsens during movement, especially if the spine is bent backward.

If a slipped vertebra compresses a nerve, symptoms may include tingling, numbness, or weakness in the buttocks and legs. Because nerves are responsible for muscle movement, a pinched nerve in the lower back may cause tight or stiff muscles in the hamstrings or buttocks.

At NYU Langone, neurosurgeons, neurologists, and orthopedists who specialize in treating the spine collaborate to confirm the diagnosis.

Medical History

A doctor asks about your medical history to help determine whether a slipped vertebra is causing your symptoms. You may be asked to describe when you first noticed pain, where it is located, and whether it occurred suddenly after an activity, such as playing sports or lifting a heavy object, or if symptoms appeared gradually.

Physical Exam

Your doctor performs a physical examination to look for the cause of your symptoms. This involves gently manipulating the legs in different extended positions to see if a particular movement causes pain and pressing against the spine to check for tenderness. This may help the doctor determine the location of a back injury and assess the severity of symptoms.

The doctor may also ask you to bend or walk a few steps to assess the tightness of your hamstrings and whether the condition has affected your gait, balance, or movement.

Neurological Evaluation

A neurological evaluation helps your doctor determine whether nerve damage is contributing to your symptoms. Nerves that originate in the spinal cord travel through the body, affecting muscles in predictable patterns. Doctors use these patterns as a guide in matching atypical physical responses with particular nerves.

Your doctor may use a small hammer to test for unresponsive nerve reflexes in various parts of your body, which may indicate that a slipped vertebra is pinching a nerve. A doctor may also expose areas of your skin to stimuli, such as warm and cool temperatures, to assess whether sensation is affected.

X-ray

An X-ray, which uses electromagnetic waves to produce images of the body, can reveal a vertebra that has slipped forward. The images can also highlight fractures in the surrounding spinal bones. Your doctor may ask you to stand and sit in different positions while X-rays are taken. This provides more information about the severity of the slipped vertebra and the impact on surrounding bones. In many cases, an X-ray may be the only test needed to diagnose spondylolisthesis.

CT Scan

If an X-ray reveals that a bone has moved forward in your spine but your doctor needs to visualize the vertebrae in more detail, a CT scan may be necessary. This test uses X-rays and a computer to create three-dimensional, cross-sectional images of the spine. A CT scan gives doctors more information about a possible fracture in the pars interarticularis, the bones that help keep vertebrae in place.

MRI Scan 

An MRI scan uses a magnetic field and radio waves to create computerized, three-dimensional images of your spine and the surrounding soft tissues, such as nerves and muscles. If your symptoms indicate the possibility of a compressed nerve, doctors may use an MRI to determine whether a slipped vertebra has pinched a nerve or to identify swelling in a spinal bone, which may indicate a fracture.

Bone Scan

For people with signs and symptoms of spondylolisthesis, NYU Langone doctors may recommend a bone scan to determine whether a fractured vertebra is actively healing or is an old injury.

First, a technician injects a small amount of dye, called a tracer, into a vein in your arm. The dye travels through the bloodstream and accumulates in places in the bone where your cells and tissues are repairing injuries.

After one or two hours, a radiologist scans your body using a camera that captures images of the tracer. If the tracer accumulates at the site of the fracture, this usually indicates that the injury is actively healing. This information may help doctors confirm a diagnosis and recommend the most appropriate treatment.