Introduction: Degenerative Spondylolisthesis (DS) refers to the anatomic defect in the vertebral pars interarticularis which leads to displacement of one vertebral body over the adjacent one. While standing and flexion extension x-rays are preferred for evaluating instability, a supine MRI is performed to identify signal changes in the cord and to identify additional pathologies. In the present study, we have presented a quantitative comparison of Meyerding grading of spondylolisthesis between lateral standing X-rays and supine MRI.
Methods: We retrospectively queried all patients diagnosed with spondylolisthesis in 2016. Only those cases were selected which had preoperative X-ray and MRI available for review. Primary variable of interest was the degree of slippage as per the Meyerding method, measured independently by 2 reviewers on lateral X-ray and sagittal MRI cuts. Agreement between the two reviewers was assessed using the two-way intraclass correlation coefficient (ICC). Agreement of Meyerding grade between the two imaging techniques was assessed using Cohen’s Kappa while the slip percentage measured for each technique was compared using a Bland-Altman (BA) plot, mean difference (MD) and one-way ICC.
Results: After applying exclusion criteria to 1069 cases of spondylolisthesis identified in 2016, a total of 273 cases were considered eligible for analysis. ICC between the two reviewers was found to be 0.75 (95%CI=0.64-0.83, p<0.001) for X-ray and 0.76 (95%CI=0.66-0.83, p<0.001) for MRI showing good agreement. Agreement between X-ray and MRI for grading of spondylolisthesis was found to be poor (Kappa= 0.32, p<0.001). BA plot between X-ray and MRI measurements revealed a MD of 4.3% (95% limits of agreement=-1.03-18.9) with 5.56% observations outside the limits of agreement and one-way ICC of 0.35 showing poor agreement.
Conclusions: Our results demonstrate the discrepancy of spondylolisthesis grade measurements between X-ray and MRI. Careful evaluation of both imaging technique is warranted to determine the final severity of pathology and tailoring of management plan.
Patient Care: This study will contribute to selecting one radiology modality over the other as a choice to diagnose spondylolisthesis. This can help in preventing undue investigations and healthcare providers’ visits; both associated with a financial burden primarily to patients as well as to the overall healthcare system including medical center facilities and insurance providers.
Learning Objectives: • Modality of choice to diagnose spondylolisthesis needs to be selected to prevent undue investigations and healthcare providers’ visits.
• Significant disagreement is found between supine MRI and erect X-Ray in evaluating patients with spondylolisthesis.