Pars Interarticularis Injury

What is Pars Interarticularis Injury?

Damaging the pars interarticularis, a portion of the spinal vertebrae, is a common cause of lower back pain. It’s especially frequent in teenage athletes. Occasionally, these injuries occur without causing any symptoms, and they’re only discovered in adulthood when the damage becomes chronic and leads to pain.

The issues linked to the pars interarticularis can vary, starting from bone stress and small fractures, known as spondylolysis, to an advanced condition known as isthmic spondylolisthesis, where one vertebra slips forward over the one below it. Bone stress is often the first sign of these problems. Ongoing bone stress leads to bone reshaping and could result in spondylolysis. Additionally, roughly 25% of spondylolysis cases visible on x-ray images are associated with spondylolisthesis.

Spondylolisthesis is a condition related to spondylolysis, which involves the sliding forward of the upper vertebra onto the vertebra below. Various types of this condition have been identified: Type I is due to a birth defect of sacrum bone’s specific process. Type II occurs due to an injury to the pars interarticularis. Type III originates from a joint problem without any fracture in the pars. Type IV happens due to an acute fracture elsewhere in the posterior spinal arch. Type V is linked to bone disease in the posterior arch of the vertebra. Type VI, which is generally a result of spinal surgery. This article will primarily focus on Type II or isthmic spondylolisthesis.

According to the scale developed by Meyerding et al., spondylolisthesis is classified into five subcategories based on how much the upper vertebra has slipped relative to the vertebra below it. It ranges from Grade I (less than 25% slippage) to Grade V (the two vertebrae no longer make contact). Most frequently, the injuries to the pars or spondylolysis occur at the 5th lumbar vertebra (85-95% of cases), with the 4th lumbar vertebra being the second most commonly affected (5-15%). Other spinal regions are less frequently involved. The injury is on just one side in about 22% of the cases.

What Causes Pars Interarticularis Injury?

A pars defect is a condition that usually starts when someone is young. However, it’s often linked with birth defects like spina bifida occulta.

While the pars injury is not something a person can be born with, studies suggest that genetics might play a role. For instance, researchers found that family members of people with a condition called spondylolysis are more likely to have it compared to others.

A specific type of this condition, called isthmic spondylolysis, is actually a small break in a part of the spine, which is the weakest part of the back of the spinal bone. This can happen due to stress from repeated back bending and twisting.

It’s less common for a single injury to cause this condition. However, an injury could worsen an already developing small break.

Athletes are among the most common group of people to experience this condition, as certain sports involve movements that increase stress on the spine. Studies have shown that the back part of the spine grows stronger until about age 50. However, children and adolescents are more likely to experience small breaks in their spine due to tiring activities.

Risk Factors and Frequency for Pars Interarticularis Injury

Spondylolysis is a condition affecting about 3 to 6% of the general population. However, its occurrence rises to 8 to 15% in elite adolescent athletes. This condition is relatively more common in males than females, with the male-to-female ratio being 2 or 3 to 1. Certain athletes, such as divers, rowers, gymnasts, weight lifters, wrestlers, and track and field throwers, have higher incidences of spondylolysis.

According to a study by Roche and Rowe, the overall incidence is 4.2%, with rates being 6.4% for white males and 2.3% for white females. Lower incidences were noticed among African-Americans, with 2.8% for males and 1.1% for females.
Reports by Fredrickson et al. reveal an escalating incidence with age: 4.4% at the age of six, 5.2% by the age of 12, and 6% by adulthood.
No newborn within the studied group of 500 patients demonstrated radiographic signs of this condition. However, family members of those affected by spondylolysis have a higher incidence than the general public.
About 80% of patients with spondylolysis at the L5 level (the lowest vertebra in the lumbar spine) have a type called isthmic spondylolisthesis. Out of this group, 20% exhibit slippage exceeding 25%.

Signs and Symptoms of Pars Interarticularis Injury

Spondylolysis, a condition identified by spine abnormalities, is common when looking at medical imaging but most people who have it don’t experience symptoms. However, it can pose problems, particularly for physically active teenagers.

This condition can occur due to various activities that involve extreme bending or twisting the spine, like weightlifting or aerobic gymnastics. Other sports can also increase the chance of injury to the spine.

The most common symptom is lower back pain, which can be either focused in one area or more widespread. The pain usually gets worse when the person is moving their spine a lot and gets a bit better when they’re resting. This pain is typically in the lower back, but some people also experience it in the buttocks or legs. The pain can start suddenly after an injury or slowly develop over a long period.

During a physical examination, the person might have excessive curvature of the lower spine. It’s also common for them to have tightness in the back of the leg muscles and bending limitations in the knees. Sometimes, the person might have a less curved lower spine, a noticeable bump on a part of the spine, or difficulties in bending or extending the lower back.

One particular test, called the Stork test or one-legged back extension maneuver, is often used during the examination. The person is asked to stand on one leg and arch their back, keeping the leg straight and leaning the upper body backward. If this movement causes pain, the person might have spondylolysis on the same side as the leg they’re standing on.

If the person only has spondylolysis, nervous system symptoms should technically be absent. However, some individuals with the condition may report leg nerve-associated symptoms such as pain, weakness, tingling and numbness. This is usually linked to a related condition known as spondylolisthesis (where a vertebra slips out of its proper position). In some cases, spondylolysis can lead to a hunched posture due to patients reflexively trying to ease their symptoms. The displacement of vertebra can put pressure on nerves making bending easier for them. If leg pain is present, the affected nerve is usually the L5. In some cases, the straight leg test may be positive. Serious symptoms such as loss of bowel and bladder control or a group of symptoms known as cauda equina syndrome are rare.

Testing for Pars Interarticularis Injury

If you’re suspected to have a lesion on the pars (a small bone structure in the spine), there are several imaging tests that can help confirm it. The first step is usually a physical examination and gathering of your medical history. Then, doctors will likely perform radiography, which involves taking images of your body’s internal structures with X-rays. In about 80% of cases, defects in the pars can be seen on these lateral lumbar X-rays. An oblique X-ray, which gives a slanted view, is frequently used to spot this condition.

If X-rays don’t provide sufficient insights, considering further tests may be useful. One of these alternatives is scintigraphy, a type of imaging where a small amount of radioactive material is injected into the body to create detailed images. This test is particularly good for detecting acute injuries and reactions in the pars for children or adolescents experiencing back pain. However, it’s not always perfect and some lesions might not show up.

A computed tomography scan or CT scan can also be helpful in some cases since it gives more detailed pictures and can indicate whether the injury is new or chronic. This scan can even assist in identifying patients who are in the earliest stages of the disease and hence, have a higher possibility of recovery, if the issue is addressed promptly.

If plain radiographs don’t clearly show any issues, SPECT (Single-Photon Emission Computed Tomography) is usually the next choice. This type of scan uses a radioactive substance and a special camera to create 3D images. Although it can point out potential issues in the spine apart from a pars lesion, like infection or bone tumors, it’s not particularly specific.

Magnetic resonance imaging or MRI is another method that can help visualize other potential causes of lumbar pain and might detect swelling in the pars. An MRI does not use ionizing radiation, like x-ray and CT scan, which can be beneficial for certain groups like adolescent females. However, it doesn’t show whether a bone lesion is metabolically active and is less accurate than a scintigraphy or SPECT.

The ideal method for diagnosing pars injuries isn’t definitively established in the medical field. The standard recommendation includes starting with an X-ray, and if needed, following it with a scintigraphy or SPECT. A positive SPECT usually indicates a need for a CT scan, while a negative one suggests the back pain isn’t due to a pars injury and doctors may then consider an MRI to investigate other possible causes.

Treatment Options for Pars Interarticularis Injury

In the medical field, there’s no agreement on whether an injury to the pars – a small part of the vertebra – should be treated conservatively or surgically. Studies conducted by researchers named Morita and Sairyo have tried to better understand healing rates by categorizing the injury levels as early, progressive, or terminal based on radiograph or CT scans.

They found that healing rates were much higher in early-stage injuries. Advanced stage injuries called terminal-stage injuries didn’t show much healing. The healing rate with conservative treatment – meaning non-surgical methods – was highest in the early stages (73%) and dropped to 38.5% in progressive stages and to 0% in terminal stages.

Other studies also found higher healing rates in cases with single-sided pars defects compared to cases with defects on both sides. Young patients with conditions called spondylolysis or low-grade spondylolisthesis – both relating to the spinal bones – generally start their treatment with conservative methods. These methods may involve wearing a brace, limiting activities, physical therapy, and controlling pain.

Conservative treatment often involves wearing a back brace almost constantly for six months, decreasing usage over the next six months, and participating in physical therapy. The therapy activities could include exercises to stretch and strengthen certain muscles, paired with close monitoring of certain conditions that have a high likelihood of worsening.

Surgical treatment for these spinal conditions is usually considered only for patients who don’t improve with conservative treatment or who are at the terminal stage. Roughly 9% to 15% of these cases require surgery. Some scenarios that might call for surgery include worsening conditions, inability to control pain, development of neurological issues, and instability in certain spinal segments.

There are several surgical options available ranging from direct repair to fusion of the segments. The most preferred surgical option is direct repair because it doesn’t decrease the range of motion as much as fusion does. Some options involve techniques named after different surgeons, like Buck, Scott, Morscher, Louis, Tokuhashi, and Ulibarri.

Out of these, the most preferred are the techniques that involve pedicle screw hooks or rods due to their high success rate, low risk of hardware failure, absence of need for bracing after surgery, and adequate maintenance of the repair during various movements.

Surgical fusion with bone grafting is recommended in patients who have failed non-operative treatments or shown worsening symptoms, neurological deficits, and certain changes that increase the likelihood of worsening. This procedure can be done with or without a device to steady the spine. Post-operation, patients are provided with a back brace and may undergo decompression if certain clinical symptoms are present.

Recently, there has been promising development with Low-Intensity Pulsed Ultrasound (LIPUS), in addition to conventional conservative treatments, which may help achieve higher rates of successful bone union. Further studies are needed to fully understand the benefits of LIPUS, but it holds promise for future standard treatment.

A study by Arima compared LIPUS to traditional conservative treatment, finding a 66.7% success rate in the LIPUS group compared to a 10% rate in the group treated with conventional conservative methods.

Many conditions could lead to back pain. These conditions include issues related to aging, infections, swelling, tumors, and injuries. In children, back pain may indicate a serious illness like cancer or a severe infection. However, most of the time, back pain isn’t serious and will go away on its own. It’s important to look at when the pain started to help figure out if it was caused by an injury, from overuse, or due to issues with growth and development.

Sometimes, problems in the stomach or pelvis can make the back hurt too. When someone has back pain and may also have an infection or another type of disease, it’s important to have tests done. Doctors often do blood tests, inflammatory markers like ESR or C-reactive protein, and cultures to check for an infection.

Several common conditions could lead to back pain:

Conditions that cause pain at the back of the spine – e.g., Spondyloarthropathy and Spondylolisthesis and overuse injury to tissues at the back of the spine, including ligaments, muscles, and joints. People with these issues often have pain when they bend backwards and may have weak muscles, reduced movement, and tight hamstring muscles.
Pain from the Sacroiliac joint which is at the lower back and buttock region. This could be due to inflammation or stress fracture, where the pain worsens with bending, standing or sitting for extended periods. Rest, ice, and anti-inflammatory medications can help manage the pain. Inflammation due to rheumatism should also be considered.
Conditions that cause pain in the front of the spine. These include Scheuermann disease, a common condition that causes a hunchback posture. This condition appears as a curved spine that doesn’t straighten when bending forwards or backwards. Other conditions include a herniated disc; although uncommon in young people, it can cause lower back or leg pain, especially when bending forwards or coughing.
Scoliosis, or a twisted spine, can also cause pain, although it’s usually painless in school-age children.
Infections like Discitis and Vertebral Osteomyelitis. Discitis is a bacterial infection that often affects children under five and causes pain in the lower back or belly. Osteomyelitis affects the bone, but is rare in children.
Inflammatory conditions like juvenile idiopathic arthritis, psoriatic arthritis, and childhood inflammatory bowel disease. These conditions are more common in boys, often associated with the genetic marker HLA-B27.
Syndromes that cause intense pain all over. These conditions don’t have a known cause but are often associated with minor injuries, chronic illness, or emotional distress.
Tumors, which are rare but need to be considered, especially if the child has severe pain, fever, weight loss, or neurological symptoms.

Please note, all of these conditions would require consultation and appropriate tests by the treating physician to confirm the diagnosis.

What to expect with Pars Interarticularis Injury

Progressive spondylolisthesis, a condition where a vertebra in the spine slips out of place, is a primary worry for patients with defects in the small, thin part of their spinal bones (known as pars). The chances of this condition worsening are generally low, around 3 to 4%. Worsening (or progression) of the condition is most commonly observed during the growth spurt in adolescence, specifically in patients who also have a minor congenital defect called spina bifida occulta.

As you get older, particularly after age 20, the risk of progression reduces due to the hardening (ossification) of the growth plate. However, research has shown that the condition is more likely to get worse if the initial slipping of the vertebra is more than 20%.

The extent to which the condition can worsen, or ‘progress’, can be significantly predicted by measuring the angle of the pelvis in cases of low-grade spondylolisthesis. In more severe cases of the condition, the angle of the pelvis is usually high. Consequently, measuring the slope of the sacrum (the bone at the base of your spine) and the tilt of the pelvis becomes more important.

Usually, young people can resume their normal activities after around six months of non-surgical treatment. However, children and teenagers with skeletal immaturity and who have the condition on both sides of their pars (bilaterally) should have standing lateral x-rays every 6 to 12 months to monitor whether the slippage is getting worse until they reach skeletal maturity. Adolescents with over 50% slip, a severe condition (Grade 3 or 4), should be referred to an orthopedic specialist. Possibly, they might need surgery.

Possible Complications When Diagnosed with Pars Interarticularis Injury

Here we discuss the complications related to this condition and the recovery period after surgery.

One potential issue following non-surgical treatment is a chronic condition where the bones in the spine do not properly fuse together, known as chronic pars defect. The chance of healing from this condition lowers over time. It may not have any symptoms or it could lead to chronic lower back pain.

Another issue that may arise from a condition called spondylolysis is when the lower spinal bone, or vertebral body, slips out of place. This is known as spondylolisthesis. This can cause lower back pain and neurological symptoms like tingling or numbness.

There are also potential complications from surgical treatment, such as:

Neurological deficit: After surgical treatment for serious spondylolisthesis, there may be neurological deficits, like weakness in the L5 nerve, which is located in the lower spine. This has been mentioned in about 30% of cases, but most of these are temporary and resolve completely.
Isthmus non-union: This happens when there is a failure in the process of the spine healing and fusing together. This is more common in patients with advanced stages of the disease.
Progression of slippage: The slippage of the lower spinal bone may get worse after surgery.
Hardware failure: There’s a chance that the medical hardware used during surgery could fail.

Preventing Pars Interarticularis Injury

If you’ve been experiencing lower back pain—especially if it’s due to repetitive sports activities and isn’t alleviated by rest—it’s important to see your family doctor. An injury to an area of the lower spine known as the pars interarticularis is a common reason for this type of pain in young people.

Recognizing this type of injury promptly and treating it effectively can help enhance your recovery in both the short and long term. It can also prevent complications that may occur from incorrect or late diagnosis.

Frequently asked questions

Pars interarticularis injury refers to damage to a portion of the spinal vertebrae, which is a common cause of lower back pain. It can range from bone stress and small fractures (spondylolysis) to a more advanced condition called isthmic spondylolisthesis, where one vertebra slips forward over the one below it.

Pars Interarticularis Injury is relatively common, affecting about 3 to 6% of the general population.

The signs and symptoms of Pars Interarticularis Injury, also known as spondylolysis, include: 1. Lower back pain: This is the most common symptom and can be focused in one area or more widespread. The pain usually worsens with movement of the spine and improves with rest. It can be felt in the lower back, buttocks, or legs. 2. Excessive curvature of the lower spine: During a physical examination, a person with spondylolysis may have an excessive curvature of the lower spine. 3. Tightness in the back of the leg muscles: It is common for individuals with spondylolysis to have tightness in the back of the leg muscles. 4. Bending limitations in the knees: Another common sign is bending limitations in the knees. 5. Noticeable bump on a part of the spine: Some people with spondylolysis may have a noticeable bump on a part of the spine. 6. Difficulties in bending or extending the lower back: Individuals with spondylolysis may experience difficulties in bending or extending their lower back. 7. Positive Stork test or one-legged back extension maneuver: The Stork test, where the person stands on one leg and arches their back, can be used during the examination. If this movement causes pain, it may indicate spondylolysis on the same side as the leg they're standing on. 8. Leg nerve-associated symptoms: In some cases, individuals with spondylolysis may report leg nerve-associated symptoms such as pain, weakness, tingling, and numbness. This is usually linked to a related condition called spondylolisthesis, where a vertebra slips out of its proper position. It is important to note that serious symptoms such as loss of bowel and bladder control or cauda equina syndrome are rare in spondylolysis.

A pars interarticularis injury can occur due to stress from repeated back bending and twisting, particularly in activities that involve extreme bending or twisting of the spine like weightlifting or aerobic gymnastics.

The doctor needs to rule out the following conditions when diagnosing Pars Interarticularis Injury: 1. Spondyloarthropathy 2. Spondylolisthesis 3. Overuse injury to tissues at the back of the spine 4. Inflammation or stress fracture in the Sacroiliac joint 5. Rheumatism 6. Scheuermann disease 7. Herniated disc 8. Scoliosis 9. Discitis 10. Vertebral Osteomyelitis 11. Juvenile idiopathic arthritis 12. Psoriatic arthritis 13. Childhood inflammatory bowel disease 14. Syndromes that cause intense pain all over 15. Tumors

The types of tests that are needed for Pars Interarticularis Injury include: 1. Radiography: This involves taking X-ray images of the body's internal structures, particularly lateral lumbar X-rays and oblique X-rays, to detect defects in the pars. 2. Scintigraphy: A type of imaging that uses a small amount of radioactive material to create detailed images, which is particularly useful for detecting acute injuries and reactions in the pars. 3. Computed Tomography (CT) scan: This scan provides more detailed pictures and can indicate whether the injury is new or chronic, helping to identify patients in the earliest stages of the disease. 4. Single-Photon Emission Computed Tomography (SPECT): This scan uses a radioactive substance and a special camera to create 3D images, which can point out potential issues in the spine, including pars lesions. 5. Magnetic Resonance Imaging (MRI): This method can help visualize other potential causes of lumbar pain and might detect swelling in the pars, although it is less accurate than scintigraphy or SPECT. The standard recommendation for diagnosing pars injuries includes starting with an X-ray, followed by scintigraphy or SPECT if needed. A positive SPECT usually indicates a need for a CT scan, while a negative one suggests exploring other possible causes with an MRI.

Pars Interarticularis Injury can be treated either conservatively or surgically. Conservative treatment methods include wearing a back brace, limiting activities, participating in physical therapy, and controlling pain. Surgical treatment is usually considered for patients who do not improve with conservative treatment or who are at the terminal stage. Surgical options range from direct repair to fusion of the segments, with the most preferred option being direct repair using pedicle screw hooks or rods. Surgical fusion with bone grafting may be recommended for patients who have failed non-operative treatments or shown worsening symptoms. Low-Intensity Pulsed Ultrasound (LIPUS) is a promising development that may help achieve higher rates of successful bone union when used in addition to conventional conservative treatments.

The side effects when treating Pars Interarticularis Injury can vary depending on the treatment method used. Side effects of non-surgical treatment: - Chronic pars defect: The bones in the spine may not properly fuse together, leading to chronic lower back pain. - Spondylolisthesis: The lower spinal bone may slip out of place, causing lower back pain and neurological symptoms like tingling or numbness. Side effects of surgical treatment: - Neurological deficit: After surgery for serious spondylolisthesis, there may be temporary weakness in the L5 nerve located in the lower spine. - Isthmus non-union: Failure in the healing and fusion process of the spine, more common in advanced stages of the disease. - Progression of slippage: The slippage of the lower spinal bone may worsen after surgery. - Hardware failure: There is a chance that the medical hardware used during surgery could fail.

The prognosis for Pars Interarticularis Injury varies depending on the severity of the injury and the individual's age. Here are the key points to note: - The chances of the condition worsening or progressing are generally low, around 3 to 4%. - Progression of the condition is most commonly observed during the growth spurt in adolescence. - The risk of progression reduces as individuals get older, particularly after age 20, due to the hardening of the growth plate. - The initial slipping of the vertebra is a significant factor in determining the likelihood of the condition worsening. If the initial slipping is more than 20%, the condition is more likely to progress. - Young people can usually resume their normal activities after around six months of non-surgical treatment. - Children and teenagers with skeletal immaturity and bilateral pars interarticularis injury should have regular x-rays to monitor whether the slippage is getting worse until they reach skeletal maturity. - Adolescents with severe conditions (Grade 3 or 4) should be referred to an orthopedic specialist and may require surgery.

Orthopedic surgeon or spine specialist.