Radiological analysis of degenerative lumbar scoliosis in relation to pelvic incidence.

PURPOSE The purpose of this study was to identify the influence of pelvic incidence (PI) on spinopelvic parameters in patients with degenerative lumbar scoliosis (DLS) and compare them with those of a normal population. METHODS There were two groups in this study. One group was composed by 136 patients with DLS and another was composed by 120 participants free of spinal disease. In each group there were three subgroups according to PI, which were low (PI less than 45°), middle (PI between 45° and 60°) and high PI group (PI more than 60°). Sagittal spinopelvic parameters were compared between the DLS patients and asymptomatic participants in each PI group. RESULTS The number of DLS patients with low, middle, and high PI were 38 (27.9%), 50 (36.8%), and 48 (35.3%), respectively. In the control group, the number of low, middle, and high PI participants were 52 (43.3%), 41 (34.2%), and 27 (22.5%), respectively. There were significant difference in PT, SS, LL, SVA and TLJ between the three subgroups in the DLS patients. Patients with high PI showed large TLJ, LL, PT, SS and small SVA. In the Control group and DLS group, PI determined pelvic orientation (PT, SS) and sagittal spinal parameters (LL, TLJ). In terms of correlation between SS and LL, between SS and TLJ, both DLS and Control groups showed significant correlations. In terms of correlation between PT and SVA, between PT and TLJ, only the DLS group showed a significant correlation. Compared with the asymptomatic participants, DLS patients showed a high PT and low SS as well as kyphotic TLJ, lumbar hypolordosis and thoracic hypokyphosis in all PI groups. CONCLUSIONS The changes in spinopelvic parameters and pelvic compensatory mechanisms differ according to PI in patients with DLS, restoration of LL based on individual PI could help in accomplishing a balanced spinopelvic alignment.