Impact of Individual Spinopelvic Anatomy on the Localization and Severity of Symptomatic Isthmic Spondylolisthesis

Abstract

Study Design Retrospective analysis of prospectively collected data. Objectives Isthmic spondylolisthesis (iSPL) occurs most commonly in L5/S1 and L4/5. This study investigates the association between spinopelvic anatomy and the pathogenesis of iSPL. Methods Spinopelvic parameters as well as severity of slip grade were measured in sagittal spine radiographs of symptomatic patients with iSPL in segments L4/5 and L5/S1. Means were calculated and differences between both groups were analyzed. A correlation between the analyzed parameters and degree of slippage was performed. Results We included 73 subjects in this study; 11 in L4/5 group and 62 in L5/S1 group. Pelvic anatomy significantly differed between L4/5 and L5/S1 iSPL (Pelvic Incidence (PI) 54.8° vs 66.3°, P value = .006; Pelvic Radius (PR) 124.4 mm vs 137.4 mm; P value = .005 and Sacral Table Angle (STA) 101.0° vs 92.2°, P value < .001). The relative degree of slippage was significantly higher in the L5/S1 group (L4/5 29.1% vs L5/S1 40.1%, P value .022). We also observed a significant correlation between pelvic anatomy and the severity of the slip in iSPL at the L5/S1 level. Conclusions Pelvic parameters PI and STA play an important role concerning the level of occurrence and severity of iSPL. Spinopelvic anatomy determines the pathogenesis of iSPL.