Sacropelvic Parameters and L5 Spondylolysis: Computed Tomography Analysis

Study Design: Retrospective analysis of computed tomography scans. Purpose: This study aims to determine the association of sagittal sacropelvic parameters with L5 spondylolysis. Overview of Literature: The association of increased pelvic incidence (PI) and decreased sacral table angle (STA) with spondylolysis has been reported, but no study has simultaneously analyzed multiple sacropelvic variables to compare their association. Methods: In this study, computed tomography scans obtained to assess major trauma in patients aged >16 years were analyzed. Scans meeting one of the following criteria were excluded: abnormal anatomy, previous spine or hip/pelvis surgery, or spinal pathology, including deformity, infection, tumor, or trauma. sacral anatomic orientation (SAO), PI, pelvic thickness (PTH), femoro-sacral posterior angle (FSPA), STA, and sacral kyphosis (SK) were measured. Results: Overall, 202 scans were analyzed: 25 with L5 spondylolysis and 177 normal. Among the groups, a significant difference was observed in SAO (43.3 degrees vs. 51.6 degrees), PI (61.7 degrees vs. 49.8 degrees), STA (95.4 degrees vs. 101.8 degrees), and SK (31.0 degrees vs. 23.7 degrees). Based on the logistic regression analysis, only PI (odds ratio [OR], 1.074; 95% CI, 1.026-1.124) and STA (OR, 0.822; 95% CI, 0.734-0.920) remained significant predictors for the presence of spondylolysis. In the spondylolysis group, PI correlated significantly with PTH (r =-0.589), FSPA (r =0.880), and SK (r =0.576), whereas in the normal group, PI correlated significantly with FSPA (r =0.781) and SK (r =0.728). Conclusions: By simultaneously assessing multiple sacropelvic parameters, we associated increasing PI with L5 spondylolysis. Decreasing STA, which likely represents a chronic remodeling secondary to spondylolysis, was also associated with increased risk. Back pain in an adolescent or young adult with high PI or low STA should raise suspicion of a possible occult spondylolysis.