Spondylolysis and spondylolisthesis in pediatric patients

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Define spondylolysis.

Spondylolysis is a unilateral or bilateral defect in the region of the pars interarticularis that may or may not be accompanied by vertebral displacement. The origin of the term spondylolysis is from the Greek words spondylo (vertebra) and lysis (break or defect).

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Define spondylolisthesis.

Spondylolisthesis refers to anterior displacement of the cranial vertebral body in relation to the subjacent vertebral body. The origin of the term is from the Greek words spondylo (vertebra) and olisthesis (movement or slippage). The deformity not only involves the olisthetic vertebra but affects the entire spinal column above the level of slippage as the entire trunk moves forward with the displaced vertebra. Slippages <50% are referred to as low-grade spondylolisthesis while slippages ≥50% are referred to as high-grade spondylolisthesis.

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Define spondyloptosis.

Spondyloptosis refers to a slippage of the L5 vertebra in which the entire vertebral body of L5 is located below the top of S1. It is the most severe degree of slippage possible. Fortunately, this condition is quite rare. The origin of the term is from the Greek words spondylo (vertebra) and ptosis (to fall).

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What is the current state of evidence regarding the etiology and prevalence of pediatric lumbar spondylolysis?

Evidence supports that pediatric spondylolysis is an acquired fracture of the pars interarticularis, which may occur unilaterally or bilaterally. The prevalence of spondylolysis in the general pediatric population is between 3% and 7%. Variability exists in the prevalence of spondylolysis. Spondylolysis does not occur in a uniform distribution across populations and is more common in males than females, in the offspring of first-degree relatives with the condition, and in certain ethnic groups, with the highest prevalence in the Eskimo population (28%). Spondylolysis is the most common diagnosis in pediatric athletes presenting with low back pain, especially those who participate in sports requiring repetitive hyperextension.

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Describe common symptoms and physical examination findings in a pediatric patient who presents with symptomatic spondylolysis.

Patients may present with localized acute or chronic low back pain. Pain is usually exacerbated with activity and hyperextension. Pain may radiate to the buttocks or posterior thighs. Radicular symptoms are uncommon, but may occur. Findings that may be present on physical examination include localized tenderness to palpation, back pain exacerbated by hyperextension and rotation, and a positive single-leg hyperextension test.

6

What imaging studies are indicated for evaluation of a patient with suspected spondylolysis?

Initial radiographic assessment should consist of standing posteroanterior (PA) and lateral lumbosacral radiographs or low-dose slot scanner images. Oblique views of the lumbosacral region are not indicated as they do not improve diagnostic sensitivity or specificity and increase radiation exposure. For patients who require additional imaging studies, magnetic resonance imaging (MRI) or computed tomography (CT) are preferred as the next imaging test after radiographs rather than a bone scan with single-photon emission CT (SPECT), which is associated with substantial radiation exposure. Literature recommends choosing the subsequent imaging modality based on the time course of symptoms, and supports use of MRI in patients with early symptoms, and CT in patients with persistent symptoms.

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What are the advantages and disadvantages of CT for the assessment of spondylolysis?

CT plays a role when a pars defect is suspected on a clinical basis but is not evident on plain radiographs or MRI. CT remains the optimal test for assessment of osseous anatomy. However, CT is unable to identify early-stage acute stress reactions involving the pars interarticularis associated with marrow edema or microtrabecular fracture. A limited-window CT scan provides a lower radiation dose than a bone scan and similar radiation dose to oblique lumbar radiographs. However, to minimize radiation exposure from CT for the pediatric patient it is necessary to utilize a low-dose protocol and restrict the scan to the anatomic region of interest.

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What are the advantages and disadvantages of MRI in the assessment of spondylolysis?

Advantages of MRI compared with plain radiography include increased sensitivity, ability to visualize soft tissue and neural structures in multiple planes, and lack of exposure to ionizing radiation. MRI is able to identify early stress reactions involving the pars region, as well as chronic pars defects, evaluate associated lumbar disc pathology, and can rule out other serious causes of back pain, such as tumors or infection. However, the sensitivity of MRI is highly dependent on the specific imaging protocol utilized and may fail to detect spondylolysis unless sagittal thin section T1- and T2-weighted sequences, as well as T1 and T2 fat-suppression sequences, are obtained.

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What are the advantages and disadvantages of nuclear imaging studies for the assessment of spondylolysis?

Technetium bone scan, SPECT, or SPECT-CT are imaging options when clinical findings suggest a pars defect but radiographs are negative. Nuclear imaging studies are helpful for diagnosis of stress reactions in the pars region and acute fractures, but less helpful for chronic lesions. As bone scans deliver seven to nine times the effective radiation dose compared to AP and lateral lumbar radiographs, these modalities are utilized less frequently today than MRI or CT.

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