By Christopher Graves, MD

Although it was once thought that back pain was uncommon in children, it is now known that it is also a common occurance in children and adolescents, with one study showing up to 20% of children will report an episode of low back pain over the course of two years. The causes of back pain in children differ somewhat in likelihood from adults, as in general children do not suffer from arthritis, which can cause back pain in adults.

One of the most common causes of low back pain in children is a problem with a tiny section of bone in between the facets called the “pars intraarticularis.” (Figure 1 from orthoinfo.aaos.org) . It sits between the facet joints in the posterior part of the spine. The pars is particularly susceptible to injury in young people, particularly in athletes. Injuries to this area range from tiny, nearly invisible cracks called “stress fractures” to complete fractures called a spondylolysis (pronounced Spon-dee-low-lye-sis), also known as a “pars defect” or “pars fracture”. This complicated sounding word makes much more sense when you break in down into its components – “spondyl” which means spine bone and “lysis” which means to break.

The pars is an important stabilizer of the posterior part of the spine. It acts to prevent one of the vertebral bodies from slipping forward on another. When this slipping of one vertebrae happens it is called a “spondylolisthesis” (spondyl = spine bone and -olisthesis means “slipped forward”, so again this makes sense!)

This thin section of bone is more susceptible to trauma, especially in the young growing spine. The reason for this is not entirely known, but there is thought to be a congenital disposition to these fractures in some people. In fact, this injury runs in families, with up to 30% of first degree relatives (parents and children) of people who have had a pars defect also having one.

Young people who participate in athletics, particularly athletes who have extension type activities are some of the most likely people to have this injury. These include football players, wrestlers, dancers, and swimmers. This has to do with the “extension type activities” which put pressure on the posterior elements of the spine, including the pars.

One of the most common clinical scenarios I have encountered with this injury involves young athletes who are lifting weights, and feel a “pop” in their back, or football players who are making a tackle and have a sudden onset of back pain. The immediate pain often quickly subsides, and so it is mistaken for a muscle strain or sprain. In many cases these injuries have a delay in diagnosis, as the immediate pain subsides, but it is replaced with an aching pain which is present during activities. Many times these young patients have suffered for months with back pain, often limiting their participation in sports that they enjoy.

Diagnosis

The first step in diagnosis of this injury is always a good history and physical exam. Understanding the patient’s family history, including a family history of significant low back pain can often be a clue to look for this pathology. A detailed history describing exactly what happened and what treatments have been tried is also critical to being able to come up with a good treatment plan.

A physical exam is the next step in workup, making sure that a patient does not have numbness or weakness in the legs (a sign of possible nerve compression), altered reflexes, or other neurologic symptoms. Patients with this problem sometimes present with “tight hamstrings”, or contractures of the hamstring muscles, which prevent them from being able to touch their toes.

One of the more specific tests for a pars defect is a test that involves standing on one leg and extending your back. If this reproduces the pain, it is fairly specific for pathology in the posterior elements of the spine such as the pars and facet joints.

After the physical exam, if I am suspicious for a pars fracture the next step in diagnosis is ordering a special set of xrays called an “oblique lateral”. This xray shows the pars on profile, and makes it relatively easy to see if they are fractured. Sometimes if it is not clear that the pars are fractured, other tests such as MRI, CT scan, or a special test called a SPECT scan can be ordered which are very sensitive for detecting pars injuries that have not completely broken through the bone, such as stress fractures.

Treatment

When an injury to the pars is found, the first line of treatment is bracing. The exact type of brace and the length of brace treatment is somewhat controversial, but I have had great success with using a rigid lumbo-sacral orthosis (LSO, Figure 2, from optecusa.com) for between 8 and 12 weeks. Generally the brace is worn at all times when the patient is out of bed. After the pain subsides with brace treatment, physical therapy is usually required for core strengthening. 

If the fracture is detected early enough in its clinical course, or if the bone has not completely broken through, often times you can get the injury to heal completely in a brace. This is called primary healing, and occurs when new bone bridges the broken segment. This means there is no “defect” visible on follow up imaging.

Unfortunately often times the pars fracture has been present for a while, and it is not possible to get primary bone healing with a brace. Despite the fact that the bone does not heal, the defect can be bridged with scar tissue, which is called a “fibrous union”. While not quite as strong as bone, this fibrous union can be strong enough to allow a completely normal return to activity.

Just because the pars does not heal with bone does not mean it is not strong! I have personally taken care of very high level athletes (NCAA Division I Football players tunnel syndrome and cubital tunnel syndrome (see figure 4). Some patients may want to delay a carpal tunnel surgery for various reasons and a safely placed ultrasound guided injection can allow for short term improvements.

In a very small percentage of young people, bracing is unsuccessful. Often times this is associated with spondylolisthesis (slipping forward). In these patients, we will often try to use minimally invasive surgical solutions to
treat these problems. Sometimes the pars can be repaired, especially if it is at a “higher level” (L1-L4) in the spine. The most common level to be injured though is L5, which in many cases is best treated by a minimally invasive spinal fusion surgery. In all of my patients, although especially in children, surgery is a last resort, and is reserved for patients who remain symptomatic despite at least 6 months of brace treatment.

If you believe you or a family member is suffering from a pars defect, you should discuss this with your family physician or orthopedic surgeon. All of the physicians at the Orthopedic Center of Illinois are trained in evaluating for pars defects. We will be happy to help you get the right diagnosis and treatment, and back in the game!