Rationale

Diagnostic imaging is essential for establishing a distinct diagnosis for back pain with hyperextension. Patients who present with classic history and physical examination consistent with spondylolysis may be treated with a presumptive diagnosis for six weeks. However, if pain persists then diagnostic imaging should be performed. The ideal imaging modality providing the best accuracy with the least radiation exposure to assess for spondylolysis in adolescent patients is unclear.

Clinical comment

Diagnosis of spondylolysis in adolescent patients with persistent low back is challenging. Imaging is needed, but the ideal imaging modality must be accurate and minimize ionizing radiation exposure in the assessment, diagnosis, and treatment of this condition.

Available literature and quality of the evidence

Systematic reviews and retrospective cohort studies exist to answer this question.

Findings

The difficulty in the assessment of pediatric spondylolysis lies in the desire to choose an imaging study with the best diagnostic accuracy while limiting radiation exposure to the patient. Plain radiographs are readily available and relatively low radiation, but controversy exists as to whether two (anteroposterior [AP] and lateral) versus four views (AP, lateral, and obliques) are needed for optimal diagnostic accuracy. Beck and colleagues investigated this issue with a retrospective cohort study looking at the diagnostic value of these two types of radiographic imaging studies. They found no significant difference in either imaging technique in regards to the test characteristics. Two view radiographs had an accuracy of 0.81, sensitivity of 0.59, a specificity of 0.96, and positive and negative predicative values of 0.91 and 0.78. Four view radiographs demonstrated comparative values of 0.78, 0.53, 0.94, 0.85, and 0.76, respectively.¹

While computed tomography (CT) scanning is thought to be more accurate then magnetic resonance imaging (MRI) in the assessment of pediatric spondylolysis, Campbell and colleagues assessed the diagnostic accuracy of CT and single‐photon emission computerized tomography (SPECT) imaging to that of MRI in 72 pediatric patients with acute low back pain. These authors found MRI was able to diagnose pars abnormalities in 98% (39/40) of pars defects found on CT/SPECT. Concordant defect grading between MRI and CT/SPECT was seen in 73% (29/40) of cases.² While both normal anatomy and complete pars fractures were readily identified on both CT/SPECT and MRI, incomplete fracture identification remained challenging with MRI. Similar findings were found by Masci and colleagues in their investigation of 71 subjects with acute low back pain. They found 80% of the pars abnormalities identified by bone scan to be seen on MRI and 95% of pars fractures identified on CT to be seen on MRI.³

Two recent systematic reviews of the literature investigating imaging for pediatric spondylolysis have been performed.⁴,⁵ Both studies indicate that it is difficult to reach any conclusions based on review of the literature because of the lack of high level evidence and variation in outcomes reporting in the studies reviewed. Despite this, both studies recommend screening for pediatric spondylolysis should start with a two‐view plan radiograph. Advanced imaging in cases of indeterminate radiographs or persistent symptoms can be done with either CT or MRI scan. While CT scan is associated with more radiation exposure, this modality may be more accurate in detecting incomplete pars fractures.

Resolution of clinical scenario

• Despite a reported low sensitively with plain radiographs, due to the availability of this imaging and the relatively low radiation exposure, screening for spondylolysis in this patient with persistent low back pain is best done with two‐view lumbar radiographs.
  
• Advanced imaging for detection of lumbar spondylolysis can be performed by CT or MRI scan when back pain persists and radiographs are negative or indeterminate. While both modalities are comparable, CT may be considered in longer courses of symptoms when incomplete fractures are more prevalent, whereas MRI should be considered in shorter‐duration cases when pars stress reaction is more likely. If the plain radiographs are normal, an MRI should be ordered to assess for pars injury in this patient.
  
• Use of SPECT bone scan in the diagnosis of extension‐induced back pain in the adolescent athlete does not seem to be supported by any evidence in light of the high radiation dose of this imaging modality.

Rationale

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