Spondylolisthesis: Slip, Ouch, and Wiltse

Spondylolisthesis occurs when one vertebrae "slips" forward relative to the one below it. Spondylolisthesis is most frequently used to describe this process in the lumbar spine, but it may occur in the cervical or thoracic spine as well.

Spondylolisthesis has traditionally been divided into categories based on the underlying pathology causing the slip (ie: the Wiltse classification). These categories include: congenital, isthmic, degenerative, traumatic, pathologic, and post-surgical (aka: iatrogenic).

Regardless of the category, the end result is the same: one vertebrae slips forward relative to the one below it. Let’s talk about each category in more detail…

Congenital spondylolisthesis occurs in children. It is usually caused by malformation of the superior articulating facet of the first sacral vertebrae (S1). The facet is a portion of bone that forms a joint with the vertebrae above or below it. Therefore, in congenital spondylolisthesis the malformed S1 facet joint is unable to form a stable joint with the lowest lumbar vertebrae (L5). The end result is that the L5 vertebrae is able to slip forward relative to the sacrum.

Isthmic spondylolisthesis occurs when there is a break in the bone that connects the facet of one vertebrae to the facet of the vertebrae immediately above (or below) it. This connecting bone is known as the pars interarticularis. The defect in the pars interarticularis is known formally as spondylolysis (see image below). Spondylolysis does not necessarily cause spondylolisthesis, but when it does it is classified as "isthmic". This type of spondylolisthesis is more common in those of Inuit heritage, as well as in athletes who have had repetitive hyperextension of the lumbar spine (ie: gymnastics, tennis, football, etc).

Traumatic spondylolisthesis is exactly what it sounds like. Injury to the facet joints, pars interarticularis, or ligaments of the spine can allow one vertebrae to slip forward/dislocate relative to the one above and/or below it.

CT lumbar spondy
Pathologic spondylolisthesis occurs when the slip is caused by some underlying pathology in the bone. This category is broad and may include tumors, osteoporosis, osteopetrosis, Paget’s disease, or other diseases of bone formation or metabolism.

Post surgical (also known as iatrogenic) spondylolisthesis occurs after surgery. It most frequently develops after a laminectomy is performed. If too much bone is removed during the laminectomy it may cause instability and allow a slip to occur.

The last category, degenerative spondylolisthesis, affects people over the age of forty. It is unclear exactly what causes this type of spondylolisthesis, but it is believed to be secondary to a combination of arthritic changes in the facet joints, degenerative disc disease, and bony remodeling of the pars interarticularis. Degenerative spondylolisthesis, unlike isthmic or congenital, usually results in the fourth lumbar vertebrae (L4) slipping over the fifth lumbar vertebrae (L5).

How Do Patient’s with Spondylolisthesis Present?

Spondylolisthesis typically presents with a combination of low back pain with or without radiculopathy (ie: discomfort down the legs). The radiculopathic symptoms are due to narrowing of the intervertebral foramen and pinching of the nerves as they exit the spinal column.

Neurological symptoms such as weakness, bowel or bladder problems, or sexual dysfunction are uncommon, but can also occur. These symptoms become more common as the severity of the slip increases.

Many patient’s with spondylolisthesis also have significant hamstring tightness (ie: unable to touch their toes). Additionally, many patients will walk or stand with their torso or knees in a flexed position.

Diagnosis and Severity of Slip

Diagnosis of spondylolisthesis is based on x-rays, CT scans, and MRI imaging. X-rays and CT scans are best at delineating the bony anatomy. MRIs are frequently ordered to assess the amount of nerve compression (especially in patients with signs of neurologic dysfunction).

The severity of the slip is based on the Meyerding classification system. Type one slips occur when less than 25% of the diameter of the vertebral body slips forward relative to the one below it. Type two slips are between 26% and 50%. Type three slips are between 51% and 75% and type four slips are between 76% and 100%. If a slip is more than 100% it is referred to as a grade five slip or spondyloptosis.

Grade 1 Spondylolisthesis L5-S1

Fix Me Doc!

Initial treatment for low grade slips presenting with back pain and mild radiculopathy is usually conservative. Physical therapy, joint injections, ibuprofen (or other non steroidal anti-inflammatory medications), and bracing can be used for several months. Physical therapy should focus on lumbar flexion exercises with avoidance of lumbar extension. If symptoms continue or worsen then surgery is indicated (talk to your local spine surgeon).

Patient’s who fail conservative treatment, have high grade slips (ie: greater than 50%), or have weakness, bowel/bladder issues, or sexual dysfunction should be offered surgery. The primary goal of surgery is to prevent further slippage by fusing the vertebrae together; realigning the spine is a secondary goal, but is not absolutely necessary. In fact, attempts to realign high grade slips have been shown to increase the risk of neurological injury.

The type of surgery offered to correct spondylolisthesis may be from the front (ie: anterior), from the back (ie: posterior), or a combination of both. As of now, there is no “right” surgical approach.

The Play by Play…

Spondylolisthesis is a fancy term that describes one vertebrae slipping forward relative to the one below. There are six categories based on the underlying pathology causing the slip. These categories are congenital, isthmic, degenerative, traumatic, pathologic, and post surgical/iatrogenic. Symptoms are typically low back pain with a component of radiculopathy. Weakness, bowel/bladder or sexual dysfunction is actually uncommon unless high grade slips are present. The Meyerding system is used to determine the severity of the slip. Treatment for low grade slips is usually conservative, but surgery may be necessary for high grade slips, patients that fail conservative management, or those with hard signs of neurological dysfunction.

Additional Pathology You Might Fancy…

References and Resources

Spondylolysis and the Scotty Dog

Spondylolysis is a fancy term for a defect in a portion of a vertebrae known as the pars interarticularis. The pars interarticularis is a section of bone that connects the superior articulating facet and the inferior articulating facet of a given vertebral body. The facets (which are joints) connect adjacent vertebrae together.

The CT scan below shows the relevant anatomy of a normal pars interarticularis and one that exhibits spondylolysis. Spondylolysis occurs about 85% of the time at the fifth (L5) lumbar segment, followed in frequency by the fourth lumbar vertebrae (L4), but it can occur elsewhere in the spine.

In spondylolysis there is a fracture/defect in the pars. Fractures of the pars interarticularis typically occur after repeated extension of the lower back. Repetitive extension causes significant pressure on the pars, which in susceptible individuals can lead to weakening of the bone.

Spondylolysis is actually quite common in gymnasts, football, and tennis players because of the repetitive back extension required of these athletes.

The importance of spondylolysis is not so much the pars defect itself, but the fact that these defects can cause one vertebrae to "slip" over the top of the one below it. When this occurs a new name is given to the condition – spondylolisthesis.

Signs and Symptoms

CT lumbar spondy
Xray Scotty Dog
The most common symptom of spondylolysis is low back pain. In fact, one of the most common causes of low back pain in individuals less than 25 years old is spondylolysis, especially in athletes. It is also important to note that spondylolysis is commonly asymptomatic.

Diagnosing Spondylolysis

Diagnosis is made by looking at an x-ray or CT scan of the spine. The classic description is a defect through the neck of the “Scotty dog”, which is seen best on an oblique x-ray of the lumbar spine.

What to do About It

Treatment starts with avoidance of the motions that caused the fracture. Occasionally a brace is used to prevent extension of the spine.

Anti-inflammatory medications like ibuprofen are commonly used if pain is significant. After a period of rest, physical therapy can be useful to strengthen muscles and prevent recurrence.

Less commonly surgical repair of the pars defect may be attempted. Surgical candidates are patients who continue to have back pain despite conservative treatment. If the patient receives significant pain relief from pre-operative bupivacaine injection into the defect, then they should be considered excellent surgical candidates.

Overview

Spondylolysis is a defect in the bony pars interarticularis of the vertebrae. It commonly occurs in the lumbar spine after repetitive extension motions. Low back pain is the most common symptom. In the absence of complications like spondylolisthesis treatment is typically conservative and involves bracing, physical therapy, and anti-inflammatories. Diagnosis is made by x-ray and/or CT scan.

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