Spondylolisthesis is a condition where one of the bones in your spine (vertebra) slips forward and onto the vertebra below it. This can happen anywhere in the spine, but it is most common in the lumbar spine.
If the bone slips far enough, it can impinge on the nerves, causing pain, and possibly numbness and weakness in the leg. The pain can range from mild to very severe. However, some people have no symptoms at all – the condition is found incidentally on a scan.
Types of Spondylolisthesis
There are several types of spondylolisthesis, but the most common are degenerative, isthmic or spondylolytic and congenital. More rare causes of spondylolisthesis include slippage caused by fracture or a tumour.
The most common type of spondylolisthesis is caused by aging and general wear and tear. As we age, the discs between the vertebra dry out and lose height, and often begin to bulge or herniate. Arthritis develops and weakens the joints and ligaments holding the vertebra in alignment. Eventually the top vertebra slips over the lower vertebra, causing a narrowing of the spinal canal (stenosis).
This type occurs due to small stress fractures in the area of your lumbar spine called the pars interarticularis. These breaks cause the vertebra to slip forward. Often these breaks occur in adolescence, but it isn’t until middle age, when the discs begin to wear that the slippage occurs.
Sometimes the vertebra don’t form normally. Congenital spondylolisthesis is the result of abnormal bone formation and so it is present from birth. The abnormal development of the vertebrae puts them at greater risk for slipping, and spondylolisthesis often occurs later in life.
Symptoms of Spondylolisthesis
Spondylolisthesis is a relatively common condition, affecting around 4-6% of the population. Many people have no symptoms at all. Often people have no symptoms until the condition progresses to the point where the slippage has begun to put pressure on a nerve. When this happens there can be pain, which may range from mild to very severe, leg numbness or tingling and even weakness in the affected leg.
Sometimes leaning forward can ease the pain, because the act of leaning forward creates more space in the spinal canal. Standing or walking often makes symptoms worse.
How is spondylolisthesis graded?
Depending on the degree of slippage, Spondylolisthesis is graded I through IV:
Grade I: 1% to 25% slip
Grade II: 26% to 50% slip
Grade III: 51% to 75% slip
Grade IV: 76% to 100% slip
Generally, Grade I and Grade II slips do not require surgery and are treated medically. Grade III and Grade IV slips require surgery if persistent, painful, slips are present.
How is spondylolisthesis diagnosed?
A plain x-ray can show the slippage of the vertebra. Sometimes MRI or CT are used, as they can provide more detailed images of the bones, ligaments, discs and nerves involved.
Treatment and management
Although non-surgical treatments can’t repair the misalignment, there are several options that patients can try to relieve painful symptoms.
Physical therapy and exercise can strengthen the lower back muscles and provide support for the vertebra.
Anti-inflammatory medications can reduce inflammation and reduce pain.
Steroid injections around the nerve or into the epidural space can decrease inflammation and swelling and therefore pain.
If non-surgical treatments have failed, surgery is an option. If the slippage is getting worse, or there are neurological symptoms (numbness, tingling, weakness or loss of control of the bladder or bowel) surgery is necessary.
Two procedures are commonly performed. A laminectomy involves opening up the spinal canal to allow more room for the nerves.
A spinal fusion fuses together the painful vertebra so that they heal into a single, solid bone. Fusing one or even two levels is quite common. Fusing 3 or more levels is major surgery and has a long recovery time. Some surgeons will not perform multi-level fusions, because the success rate is so low.
Recovery from spinal fusion is slow, it can take several months for the bones to fuse. Generally, the patient will feel better sooner, however.
Spondylolisthesis can cause chronic pain, which can lead to reduced mobility and inactivity leading to a sedentary lifestyle. This can result in weight gain, loss of bone density, and loss of muscle strength and flexibility in other areas of the body. If a slipped vertebra is pressing on a spinal nerve root, there is also the risk of permanent nerve damage.
While spondylolisthesis can’t be fully prevented, exercises that strengthen the spine, prescribed by a physical therapist, is recommended to slow progression.