A pars defect or spondylolysis is a stress fracture of bones in the lower spine. Unfortunately, these fractures normally happen because of overuse. Also, the fractures can exist on one or both sides of the vertebrae. Pars Fractures cause lower back pain in children and adolescents.

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“At Southwest Scoliosis and Spine Institute, we see adults and children in pain. Consequently, we use our expertise and experience to make a difference in improving their lives.”
Richard Hostin, MD


The bone pars interarticularis splits, resulting in a pars fracture. Spondylolisthesis occurs when one vertebral body slips or slides forward over the one underneath it due to this type of spinal fracture. This page addresses the etiology, diagnosis, and treatment of various linked lumbar disorders and explains and depicts the anatomy of the low back involved. By definition, facets are formed by two surfaces, one from each neighboring vertebra. And each vertebra has four separate joint surfaces in the back, two above the pedicles and two below the pars interarticularis (mirror images).

Stress, Structural Forces, and Pars Interarticularis

The pars interarticularis connects the joints above and below one vertebra. Doctors refer to the bony bridge that connects these two upper and lower aspects as the pars interarticularis, which means “part between the articulations” in Latin. An isthmus is a thin strip of land that connects two bigger bodies of land, as you may recall from geography. As a result, doctors refer to the pars interarticularis as an “isthmus” since the bone links between the two facet joints.”  The bottom two vertebrae of the spine (L4-S1) face down like a sled on a ski slope, and they bear the whole weight of the spine above them. The inferior facets, sometimes known as “door stoppers,” are a buttress that keeps the lower vertebra from slipping down.”

The bony pars interarticularis connects these “doorstops” to the higher structures (pedicles). As you can expect, these structures do not do well with a great deal of stress, particularly when impact occurs. Contact sports, leaping, and particularly extension can cause overload forces (bending backward). The tiny bony structures (cortical bone and trabecula) that make up the pars interarticularis might become stressed and fractured as a result of this strain.

Development of Pars Fractures

If the pars repeatedly get overloaded without enough time between episodes to enable healing, they will ultimately break (fracture) and become incompetent, similar to how bending a metal coat hanger causes it to fail. Genetics has a significant impact as well. These fractures usually affect both sides of the pars, however, they can also affect just one side (unilaterally). If only one side of the pars breaks, the opposing pars take the brunt of the stress and may eventually fracture. Because there is no protection to prevent shear stresses (slide forces) on discs, fractures can occur on both sides.

The disc acts as a shock absorber and serves as the primary cushion for spinal trauma. However, the disc has a low shear (slide) resistance. The disc is exposed to aberrant stresses that might harm it without the facets in the back to protect it. The unbroken facets prevent these stresses from occurring, and pars fractures can cause the disc to collapse.

The disc can stretch and subsequently tear under extreme tension. The above-mentioned vertebra then begins to slide forward on the one below. (The L5 vertebra, in particular, can begin to move forward on the sacrum.) An isthmic Spondylolysis (lysis meaning “cut” or “break”) happens before the sliding commences. Doctors refer to the condition as isthmic spondylolisthesis if there is a slide accompanying it (oliothesis means to slip in Latin). This fracture appears more common in teenagers who participate in contact sports or whose sport requires them to bend backward (wrestling and gymnastics come to mind).

Children with Pars Fractures

Pars interarticularis fractures affect one out of every twenty children. These fractures usually happen between the ages of 8 and 15. Many times, a child who develops a new fracture will not exhibit any severe symptoms at first or will disregard the discomfort and not inform parents, coaches, or trainers. In many children, the discomfort will subside until the disc gets injured.

Diagnosis and Healing

Pain and stiffness in the middle of the lower back indicate pars defect among other conditions as well. Pain normally gets worse with lumbar extension and twisting. Activity exacerbates symptoms, which subside with rest. Pain may radiate down one or both legs in certain patients. The nerves that exit in the spinal canal near the fracture get compressed and irritated, resulting in discomfort. Numbness, tingling, and weakness in the legs are other possible side effects. The majority of individuals with a pars defect do not require surgery and can get relief through drugs and relaxation. Pain gets treated with anti-inflammatory medicines and muscle relaxants. During the acute period of the injury, a patient should wear a lumbar corset back brace. When a patient gets diagnosed, physical therapy gets started. The therapist will begin PT by introducing a series of abdominal and low back muscle-building exercises.

Working these core muscles allows patients to move more easily and reduces the likelihood of future discomfort and issues. Patients should anticipate being in therapy sessions for 6-8 weeks and a full recovery to take up to 6 months. Steroid spinal injections may aid in more severe cases of discomfort. Patients may need surgery if nonsurgical therapy does not relieve their symptoms. Two surgical procedures for a pars deficiency involve Pars repair and lumbar fusion. The challenge with treating this disease in teenagers occurs because teenagers rarely express their grief, and the disorder does not have lots of symptoms.  In addition, this condition may get overlooked by pediatricians, but athletic trainers will spot problems and seek referral sources. Treatment becomes more challenging if the condition continues month after month.

Children and Pars Fractures

In general, children with broken bones heal very quickly. Pars interarticularis fractures, on the other hand, are the only type of fractures that do not heal well.  The following three factors provide the reason for poor healing.

  1. These fractures have a relatively limited surface area.
  2. When extensive cancellous surface regions are exposed, bone has a higher chance of mending. The “spongy bone” inside the hard cortical bone, cancellous bone, contains many bone-generating cells. Unfortunately, very little cancellous bone exists in the pars interarticularis.
  3. The spine endures some of the most extreme motion and shear pressures. Extreme pressure will cause a bone to crack. It’s tough to get an energetic youngster or teenager to relax in this location. A brace can help a youngster slow down, but it won’t immobilize the region, and mending bone cells don’t like mobility. The type of pars fracture you sustain will influence your rehabilitation.

Three types of fractures:

  1. Atrophic
  2. Hypertrophic
  3. Displaced

Atrophic fractures do not mend easily and this normally occurs because of inadequate immobilization. In this case, the ends of the shattered bone appear very thin, and the body makes a feeble attempt to bring them together. Similarly, a displaced fracture occurs when the vertebra slips forward and the shattered fragment ends do not close and meld to each other. Unfortunately, both have a low ability to heal.

The hypertrophic fracture is characterized by thick, expanded, and co-opted fracture ends (right next to each other). Furthermore, a brace gives these fractures the best chance of healing.

Unilateral (one-sided) fractures will heal quite well. Although, healing without a brace and without limiting activity negatively affects the healing process for a broken pars fracture. Even with the greatest healing fractures (unilateral and hypertrophic), the success rate with a brace and three to six months of limited activity is around 50%. Consequently, children and adults can re-fracturing a pars fracture if they resume their old level and kind of activity. Our doctors surgically treat these fractures with an excellent success rate.

If you or your loved one suffers from back pain from a spinal condition, there is hope. We can help. Call Southwest Scoliosis and Spine Institute at 214-556-0555 to make an appointment today.