The association of rod curvature with postoperative outcomes in patients undergoing posterior lumbar interbody fusion for spinal stenosis

Background: Restoration of sagittal balance is a key issue in posterior lumbar interbody fusion (PLIF) surgery and adverse postoperative outcomes are associated with inadequate restoration of sagittal alignment. However, there is still a lack of solid evidence about the impact of the rod curvature on sagittal spinopelvic radiographic parameters and clinical outcomes. Method A retrospective clinical study was conducted to compare patient characteristics between lumbar spinal stenosis patients who underwent PLIF with satisfactory postoperative results and those who had poor recovery resulted from adjacent segment degeneration after PLIF and needed revision surgery (i.e. Normal and Abnormal Groups). Patient demographics (age, gender, height, weight and BMI), surgical characteristics (number of fused levels, surgical time, blood loss and hospital stay) and radiographic parameters (lumbar lordosis [LL], sacral slope [SS], pelvic incidence [PI], pelvic tilt [PT], PI-LL, Cobb angle of fused segments [Cobb], rod curvature [RC], Posterior tangent angle of fused segments [PTA] and RC-PTA) were analyzed. Results Patients in the abnormal group had older median age and suffered more blood loss than those in the normal group. RC and RC-PTA were significantly lower in the abnormal group compared to the normal group. Multivariate regression analysis revealed that lower age and lower PTA were related to higher odds of better surgical outcomes. The receiver operating characteristic curve analysis showed that the RC classifier was a good predictor of postoperative outcomes. Conclusions The study revealed significant differences in age, blood loss, RC and RC-PTA between normal and abnormal groups, and RC was demonstrated to be a pretty good indicator for predicting postoperative outcomes.