Spondylolysis occurs when there is a crack in the bony posterior (rear) portion of the spinal column. The human spine is made up of 24 bones - called vertebrae - which are stacked on top of one another in the spinal column.
The spinal cord is protected by a ring of bone that makes up the middle and posterior portion of the spinal column. The area of injury in the spinal column is between the pedicle and lamina. (see figure 1)
This is usually caused from excessive or repeated strain to the area of the spinal column called the pars interarticularis, and it is sometimes referred to as a pars defect when fractured through this portion of the spinal column. (see figure 1)
Figure 1: Depiction of the Spinal Column and Location of a Pars Fracture
View from the side
View from the top
The lower portion of the spinal column is called the lumbar spine. Spondylolysis most commonly occurs in the lower back at lumbar vertebra number five (L5). In athletes, this type of injury can be seen when the back is bent backwards repeatedly, in activities such as gymnastics, karate, and football. Specifically, this is common in offensive and defensive linemen.
The vertebra initially responds to increased strain by gradually adding new bone cells around the injured area; however, an injury can occur too quickly for the vertebrae to be repaired, and this leads to a stress fracture. This type of fracture usually occurs in the pars and can lead to a persistent pars defect after the fracture has been completed.
The crack may affect only one side, but it is not uncommon to have fractures on both sides of the vertebra. When fractures occur on both sides, it is possible for one vertebra to translate or move forward or backward over the neighboring vertebra; this is called spondylolisthesis.
Those with a pars fracture may feel pain and stiffness in the lower back that is worsened with activity and improves with rest. Hyper-extension (abnormal stretching) of the lower back will usually aggravate the area as it overloads the pars fracture.
Occasionally, nerve symptoms can be present that may include a “pins and needles” sensation in a leg, with or without numbness or weakness in the leg.
Evaluation for this condition would include a review of the patient’s medical history and a physical exam, followed by x-rays, which can detect pars defects.
A bone scan can be used for early detection of a stress fracture of the pars. This involves injecting chemical "tracers" into your blood stream. The tracers then show up on special spine x-rays. The tracers collect in areas of increased metabolism or cell activity in bone tissue, such as would be seen in areas of a stress fracture of the pars interarticularis.
The treatment for a pars fracture is initially non-operative and includes rest and bracing. The fracture can be assessed with a series of x-rays every few months.
Bracing can last for 3-4 months while the fracture heals, and physical therapy can also be included to maintain and help strengthen the abdominal and back muscles with specific directed exercises.
If the athlete has persistent pain after non-operative treatment, surgery may be required. There are two operations that may be performed: