What is Pars Defect?
Pars defect, also referred to as spondylolysis or stress fracture, is a condition in which a fracture (break) occurs in the bony ring on the back of the vertebral or spinal column. This occurs most often in the lumbar spine vertebrae or lower back (L1 to L5). In this condition, the bone that protects the spinal canal cracks due to repeated or excessive stress.
Around 80% of pars defect occurs on both sides of the vertebra (bilateral); however, they can also occur only on one side (unilateral). More than 85% of pars defect is noted in the L5 vertebrae, with about 10% occurring in the L4 and to a much lesser degree in the L3 and L2 vertebrae.
Pars defect is a common cause of low back pain in adolescents and children. It is more common among children and teenagers who participate actively in sports such as football, weightlifting, and gymnastics.
Causes of Pars Defect
Pars defect occurs as a result of a defect or stress fracture in the pars interarticularis, the part of the lumbar spine joining the upper and lower joints. Genetic factors may have a role too. Children born with thin vertebrae are prone to vertebral stress fractures. Also, overuse of the low back mainly from sports that involve repetitive back bend-like motions or repetitive trauma to the lower back area that occurs during sports and other activities can cause weakness of the pars interarticularis, resulting in pars defect.
Signs and Symptoms of Pars Defect
Symptoms of a pars defect are stiffness and pain in the middle of the low back. Lumbar twisting and extension normally increase pain. Symptoms get worse with activity and go away with rest. Some may experience pain radiating down one or both legs. This pain comes from irritation and pressure on the nerves that exit the spinal canal near the fracture. Patients can also experience weakness, tingling, and numbness in their legs.
Risk Factors Associated with Pars Defect
Risk factors for developing pars defect may include:
- Family history of back problems
- Repetitive trauma to the lower back
- Increased lordosis (swayback)
- Incomplete development of spinal cord (spina bifida occult)
- Participation in sports such as football, gymnastics, and weightlifting that require constant overstretching of the spine
Untreated pars defect may lead to further complications including:
- Spondylolisthesis, a condition where one or more vertebrae slip out of place
- Limited mobility and inactivity
- Weight gain because of inactivity
- Loss of bone density
- Loss of muscle strength
- Loss of flexibility
- Permanent nerve damage
- Chronic back pain
- Numbness, tingling, or weakness in the legs
- Nerve compression causing problems with bowel or bladder control
Although pars defect is not completely preventable, certain factors can reduce the risk of developing the condition:
- Maintain a healthy weight to reduce stress on the lower back.
- Core exercises that keep the abdominal and back muscles strong will help to support the lower back.
Diagnosis of Pars Defect
Your physician diagnoses pars defect by asking about your symptoms and by conducting a thorough review of your physical examination and medical history. Your physician may also order imaging tests such as an X-ray of the lumbar spine to identify any fractured vertebrae and MRI or CT scans to detect small fractures or rule out other spine conditions that may cause back pain, such as a pinched nerve or herniated (bulging) disc.
Treatment for Pars Defect
Based on the severity of the pars defect, your physician may recommend either conservative treatments or surgical treatment.
Conservative treatment
The primary treatment for pars defect is always conservative. The goal of conservative treatment is to reduce the pain, allow the fracture to heal, and improve spinal function.
Conservative treatment options include:
- Rest: Adequate rest should be taken and strenuous exercises should be avoided until the symptoms subside.
- Medications: Non-steroidal anti-inflammatory drugs (NSAIDs) may be prescribed to reduce the pain and inflammation. If NSAIDs do not provide relief, epidural steroid injections may be administered to the spine to reduce pain, numbness, and tingling in the legs.
- Physical therapy: An exercise program helps to strengthen the abdominal and back muscles, improve flexibility, and increase range of motion of the lower back.
- Use of braces: In severe cases of pars defect, a brace or back support may be used to stabilize the lower back during fracture healing.
Surgical treatment
Surgery is usually required if a pars defect has progressed into spondylolisthesis. The goal of the surgery is to remove any abnormal bone compressing a nerve and to stabilize the spine.
Decompressive Laminectomy and Spinal Fusion: First, a decompression laminectomy will be done. An incision is made in the back following which a part of bone and thickened tissue causing pressure on the spinal nerves is removed. This creates more space for the nerves, thus relieving pain and pressure on the nerves. This procedure is likely to make the spine unstable and therefore another procedure, spinal fusion, is performed to stabilize the spine.
Spinal fusion is the surgical technique of combining two or more vertebrae. Fusion of the vertebrae involves the insertion of secondary bone tissue obtained either through auto graft (tissues from the same patient) or allograft (tissues from another person) to augment the bone healing process. The fusion process is followed by fixation that involves fitting of metallic screws, rods, plates, or cages to stabilize the vertebrae, which helps in preventing continued slippage and accelerating bone fusion. After surgery, 6-12 months is the ideal time for complete fusion to take place.
