The bones of your spine are arranged to give your spinal column stability. Damage or defects within the supporting structures of your lumbar spine (low back) can be a source of back pain. A crack in the bony ring of your spinal column is called spondylolysis. If the crack occurs on both sides of the bony ring, your spine is free to slip forward, which is a condition called spondylolisthesis. About five to six percent of the population is affected by these two conditions.
Spondylolysis describes a defect in the bony ring of a vertebra in your spine. It mainly affects the lowest lumbar vertebra. The bony ring, formed by the pedicle and lamina bones, protects your spinal cord and spinal nerves. The bone is weakest between the pedicle and lamina, an area called the pars interarticularis or “pars” for short. A pars defect is believed to be a stress fracture. A stress fracture happens from repeated strain on a bone. At first your body is able to heal the damage. If the repeated strains happen faster than your body can respond, the bone eventually fractures. People are not born with spondylolysis. It commonly first appears in childhood. Football linemen and gymnasts are affected the most.
Spondylolisthesis describes a vertebra that has slipped forward on the vertebra below. This usually occurs when a vertebra has a bony defect (spondylosis) on both sides of the bony ring. A crack on both sides of the bony ring separates the facet joints from the back of your spinal column. The facet joints can no longer steady the vertebra. The vertebra on top starts to slide forward, slowly stretching the disc below the damaged vertebra. In adults, there is usually no danger that the vertebra will slide off the vertebra below. But teenagers sometimes have a unique type of spondylolisthesis in which one vertebra slips forward and slides completely off the vertebra below.
Spondylolysis and spondylolisthesis can both be a source of low back pain. Yet having one of these conditions does not mean you are certain to have back problems. It does put you at higher risk compared to people who don’t have them. These conditions can cause mechanical pain–the kind or pain that comes from within the moving parts of your spine. They can also cause compressive pain, which is from pressure on the nerves in your low back.
Pinched or irritated nerves produce compressive symptoms. This occurs in spondylolysis when a lump of tissue forms around the crack. This is your body’s way of trying to heal the stress fracture. The lump can cause pressure on the spinal nerves where they leave your spinal canal. A pinched nerve called radiculopathy, can also happen in spondylolisthesis when the vertebra slides forward and squeezes the nerve. The forward slip of the vertebra also makes your spinal canal smaller, leaving less room for your nerve roots.
Pressure on the nerve can produce pain that radiates all the way down to your foot. It can also cause numbness in your foot and weakness in the muscles supplied by the nerve.
In order to make a proper diagnosis of spondylolysis or spondylolisthesis and rule out other possible conditions, your doctor will perform a history and physical exam. X-rays are often all that are needed to see a pars defect or forward slip of a vertebra. A defect on X-ray does not confirm your back symptoms are coming from the defect. X-rays will help your doctor measure any slippage from possible spondylolisthesis.
Other conditions, such as a herniated disc, may be the actual cause of your symptoms. Your doctor will carefully look for all possible causes of your symptoms, which may involve other tests. The most common tests that are ordered are an MRI to look at your nerves and spinal cord, a CT scan to get a better picture of your vertebral bones, and special nerve tests to determine whether any nerves are being irritated or pinched.
Treatment for spondylolysis and spondylolisthesis is similar to treatments for other causes of mechanical and compressive back pain. Surgery is rarely necessary. Your doctor may prescribe rest, including avoidance of sport activities, to help calm symptoms from mechanical back pain. Special braces, casts, or corsets are used to help heal a stress fracture and to ease pain.
Your doctor may also have you work with a physical therapist. A well-rounded rehabilitation program assists in calming pain and inflammation, improving your mobility and strength, and helping you do your daily activities with greater ease and ability.
Medications may be used for short periods of time to control pain, ease muscle spasms, and help you regain a normal sleep pattern (if you are having trouble sleeping). Short periods of bed rest may help with acute painful episodes.
Surgery is necessary only if conservative treatments fail to keep your pain at a tolerable level. Surgical treatment for spondylolysis and spondylolisthesis must address the presence of mechanical and compressive symptoms.
Nerve pressure may require surgical decompression, called decompressive laminectomy of the lumbar spine. In order to free up or “decompress” the nerves, your doctor must remove a section of bone from the back of your spine (lamina). Your doctor may also have to remove a portion of the facet joints. The lamina and facet joints normally provide stability in your spine. Removal of either or both can cause your spine to become loose and unstable. When this occurs, your doctor will also perform a spinal fusion. Likewise, patients needing surgery for spinal instability due to spondylolisthesis typically require lumbar fusion.