The word spondylolysis is derived from the Greek spondylos (vertebra) and lysis (break). As the name implies, a spondylolysis is a defect or break in the pars interarticularis. Spondylolysis affects roughly 3–7 % of the general population [1, 2]. Studies have pointed to genetics as possibly playing a role in development of a spondylolysis. While genetics and other factors may have a contributing role, activities that involve repetitive lumbar extension such as wrestling, boxing, rowing, diving, dancing, gymnastics, and throwing place patients at greater risk of developing a spondylolysis [3].

Spondylolysis may occur unilaterally or bilaterally. When a spondylolysis is bilateral, it places patients at significantly increased risk of that patient developing an isthmic spondylolisthesis, which is the most common form of spondylolisthesis (see Chap. 8 for more on this). Spondylolysis most typically involves the L5 segment.

Spondylolysis is thought to be symptomatic in only approximately 20 % of the population with that pathology, meaning that spondylolysis is asymptomatic about 80 % of the time [4]. Spondylolysis causing lower back pain is most common in children and teenagers and is most commonly diagnosed at the ages of 15–16. When symptomatic, the most common complaint is axial lower back pain. A spondylolysis in and of itself will not cause neurologic symptoms. However, if a spondylolysis leads to an isthmic spondylolisthesis, then a radiculopathy may result along with neurologic signs and symptoms.

Consider the following patient. John is a 16-year-old football player with progressively worsening right lower back pain. The pain is worse with standing and twisting to the right. John is a junior in high school and is in the middle of football season. He has been trying to play through the pain but the pain has been getting worse to the point where his coach finally told him that he needs to see the doctor. John denies any radiating leg pain. John denies any numbness, tingling, or burning in the legs. When John sits down during class, he has no pain. The pain has been present for 4 months, since the end of preseason, but has gotten much worse in the last 3 weeks. On physical examination, John is a healthy, muscular 16-year-old with a normal gait and no neurologic deficits. He has pain with lumbar extension and worse pain with right oblique extension of the lumbar spine. He has tenderness of the right lower lumbar paraspinal muscles.

Most spine specialists would agree that given John’s age, sport of choice, and extension biased pain, particularly lumbar oblique extension to the side of his pain causing increased pain, it is very important to evaluate John with radiographs for a spondylolysis. There are four imaging modalities to evaluate for a spondylolysis. X-rays, including AP, lateral, and oblique views, can assess a spondylolysis. CT and MRI may be used to detect more subtle defects that X-ray may miss. CT may be more sensitive than MRI for this purpose but it entails the risk of the associated radiation. SPECT scanning is the most sensitive at identifying smaller or more subtle cases of spondylolysis. Additionally, SPECT scans as well as MRI and CT can help identify the acuity of the pars interarticularis fracture and if there is only a stress reaction which may be a precursor to a true fracture [5–12].

Many spine specialists will first order plain films with oblique views of the lumbar spine included in a case such as John. If the X-rays are negative for a pars interarticularis fracture but clinical suspicion is high, then SPECT or MRI may be obtained. If a pars interarticularis is found in conjunction with an isthmic spondylolisthesis, then flexion and extension x-ray views of the lumbar spine should be obtained to rule out instability.

If a patient presents with a high degree of suspicion for a spondylolysis (such as with John) but also presents with neurologic features, then it may be best to order an MRI as this does not include radiation and will also show the soft tissues and potential for concomitant disc herniation or other pathology.

Treatment for a spondylolysis depends on the stage of the fracture. Pain medications, bracing, and rest are the cornerstone of treatments for acute fractures. Pain medications may include acetaminophen, NSAIDs, muscle relaxers, or a short course of opiates depending on the severity of symptoms.