New Computed Tomography-Based Classification of Spondylolisthesis due to Pars Defect and Comparison with Meyerding Classification.

Abstract

We propose a new classification of spondylolisthesis based on the anterior displacement of the defective pars neck relative to the inferior articular process line on parasagittal computed tomography images. We aimed to compare this classification with Meyerding grades (MGs), assess its reliability and applicability, and evaluate its clinical implications. A total of 205 lumbar computed tomography images of patients with pars defects and degenerative disc disease were included in the study. According to the algorithm, the pars listhesis grade (PLG) was determined as PLG 0 if the defective pars neck was behind the inferior articular process line, PLG 1 (mild) if it was within the line, PLG 2 (moderate) if it was entirely in front of the line, and PLG 3 (severe) if it was displaced in front of the line with the superior articular process. The rates of bilateral PLG and MG and demographic data were analyzed. Clinical data from 40 patients (10 per PLG grade) were analyzed. There was a moderate positive correlation between the PLG and MG (r = 0.46) and a strong positive correlation between right and left PLG grades (r = 0.82). Intra- and interobserver reliability showed almost perfect agreement (0.84-0.97). Clinical scores, the visual analog scale, the Oswestry Disability Index, and the SF-36 showed significant differences among PLG levels, with increased disability and decreased physical health observed with higher PLG levels. PLG classification can be used as a new grading system for spondylolisthesis, especially with low Meyerding grades.