Diagnosis of Spondylolysis

Initial Imaging Approach

The American College of Radiology recommends starting with plain radiographs (anteroposterior and lateral views) of the symptomatic spine region as the initial screening tool, with a sensitivity of 77.6% for detecting spondylolysis, followed by MRI without contrast if radiographs are negative but clinical suspicion remains high 1, 2, 3, 4
The combination of negative radiographs and negative clinical examination has a negative predictive value of 0.81, meaning approximately 1 in 5 cases may still have the condition 1, 3, 4
Oblique views should not be obtained as they double radiation exposure without significantly increasing diagnostic sensitivity 1, 2, 5

MRI is the most appropriate advanced imaging modality for suspected spondylolysis, particularly in pediatric and adolescent patients, as it avoids radiation exposure while providing high diagnostic accuracy 2, 6, 7, 5
Fat-suppressed and fluid-sensitive sequences (T2-weighted with fat saturation) are essential to identify bone marrow edema in the pars interarticularis or adjacent pedicle, which indicates active stress reaction even before a visible fracture line develops 1, 2, 3, 4
MRI can detect early stress reactions (grade 1 lesions) that are invisible on CT, allowing earlier intervention and potential prevention of progression to complete fracture 1, 3, 4
MRI provides the added benefit of evaluating for alternative diagnoses including disc herniation, apophyseal injuries, intraspinous ligamentous injury, and nerve root compression 1, 3, 4
Contrast is not indicated for evaluation of mechanical back pain due to spondylolysis 1, 3, 4

Imaging should be reserved for patients with persistent back pain lasting 4 weeks or more, particularly those with clinical red flags including constant pain, night pain, radicular symptoms, or abnormal neurologic examination 8, 6, 7
Spondylolysis is the most common cause of overuse-related chronic back pain in children and adolescent athletes 1, 3, 4

Obtain AP and lateral radiographs (no oblique views) of the symptomatic spine region 1, 2, 3, 4
If radiographs are positive, consider MRI to assess for active stress reaction, evaluate healing potential, and identify nerve root compression 1, 3, 4
If radiographs are negative but clinical suspicion remains high, proceed directly to MRI with fat-suppressed sequences 2, 6, 7, 5
CT may be added if MRI shows abnormality and precise bony detail is needed for surgical planning, or if MRI is contraindicated 1, 3, 4