Spondylolysis is a stress fracture in one of the vertebrae at the base of the spinal column. It may also be referred to as a “pars” fracture. Spondylolysis is a common cause of low back pain in adolescent athletes. It most commonly affects the fifth lumbar vertebra and is the most common cause of back pain in adolescent athletes.
The stress fracture occurs through a part of the vertebral bone called the pars interarticularis and is often broken on both sides. This part of the vertebra is very thin and has a poor blood supply, making it more vulnerable to a break. The fracture may result from a direct trauma, by a focused strain usually from athletic activity, or from a genetic weakness in this area of the bone. This thin bone can break with overuse; imagine a paperclip that has been repeatedly bent until it finally breaks.
Most commonly, pars stress fracture occurs as an adolescent, it is estimated up to 5-7% of adolescents have a pars fracture. It is extremely commonly in high impact athletes like gymnasts, dancers, lineman, wrestlers, as well as athletes experiencing great rotational forces such as tennis players, lacrosse players, and baseball players. The fracture may go undetected at the time of injury, feel like a strained back, or be very painful.
X-rays of the lumbar spine are used to evaluate the position of the vertebra and look for spondylolysis. When necessary,whole body bone scan and CT scan can be used to detect a spondylolysis that is not visible on regular x-rays. If there is evidence of pressure on the lumbar nerves, then an MRI scan may be needed to further assess the abnormality.
Initial treatment for spondylolysis is always nonsurgical. Fortunately, these fractures often heal with a period of rest and core strengthening. The patient should take a break from sporting activities until symptoms resolve to allow the bone to heal. Guided physical therapy will be initiated to improve core strengthening and lumbar motion. Anti-inflammatory medication may be used to help reduce back pain. Patient education on lifestyle modifications have been shown to be beneficial in managing symptoms. While the patient is young and their discs are still healthy, they can return to normal function and perform well with no symptoms. In most cases, activities can be gradually resumed with few complications or recurrences. Exercises for the back and abdominal muscles can help prevent future recurrences of pain by stabilizing the spine. Periodic X-rays may be needed to be sure the vertebra is not changing position.
Many people with spondylolysis do not have problems for many years as their disc continues to be healthy. With a stress fracture, there decreased posterior support in the vertebral segment causing more forces to be placed on the disc in front. This can cause degenerative disc disease, where the disc progressively breaks down to not adequately support the bone above. Disc degeneration causes supporting collagen fibers in the disc to breakdown, allowing the disc to lose water. When it begins to dehydrate, it loses height and function. As the disc narrows, the bones above and below the disc can move or slip on each other. In addition, it is possible for the fracture gap at the pars to widen, causing the vertebra to shifts forward. This forward slippage is called spondylolisthesis. Imagine a tripod stool where two back legs have been partially cut through. With time and movement, the stool would be unstable and tip forward. There is not supposed to be any movement of these bones. This movement indicates segmental spinal instability.
When we look at the spine from the side, we can imagine a scotty dog. It is outlined above. The pars fracture is seen as a collar around the dog's neck. Instability and movement can cause the neck to widen. We will see this below in an x-ray example.
Spinal Specialist, Dr. Thomas Schuler, explains common causes of back and neck pain. He differentiates sprains and strains, and discuses how disc degeneration can lead to chronic back pain. He defines active and passive stabilizers known as fractures (spondylolysis) and slippage (spondylolisthesis).