MR imaging of the pars interarticularis

Area of Science:

• Radiology
• Orthopedic Imaging
• Spine Diagnostics

Background:

• Magnetic Resonance (MR) imaging is a valuable noninvasive tool for evaluating low back pain.
• Detecting bone abnormalities, like spondylolysis, is more challenging with MR imaging compared to soft-tissue lesions.
• Spondylolisthesis evaluation often requires differentiating spondylolysis from other causes.

Purpose of the Study:

• To assess the utility of MR imaging in diagnosing spondylolysis, a common cause of spondylolisthesis.
• To identify potential pitfalls and confounding factors that can simulate spondylolysis on MR images of the lumbar spine.
• To correlate MR findings with computed tomography (CT) and plain film radiography.

Main Methods:

• Retrospective review of 14 adult lumbar spine MR images in patients with spondylolisthesis.
• Correlation of MR findings with CT scans and plain films for diagnosis confirmation.
• In-vitro study of four cadaver lumbar spines using MR and CT imaging, followed by histological sectioning.

Main Results:

• MR imaging suggested pars interarticularis abnormalities in all seven confirmed spondylolysis cases and six of seven non-spondylolysis cases.
• Spondylolysis on sagittal MR images is characterized by interrupted pars marrow signal, often with marginal sclerosis (dark signal).
• Four conditions were identified that can mimic spondylolysis on sagittal MR: pars sclerosis, facet joint spurs, post-facetectomy changes, and metastatic disease.

Conclusions:

• MR imaging can suggest spondylolysis, but its accuracy is limited by potential mimics.
• Careful interpretation of sagittal MR images, considering specific confounding factors, is crucial for accurate spondylolysis diagnosis.
• Correlation with CT and plain films remains important for definitive diagnosis of spondylolysis and spondylolisthesis.