Analysis of spinopelvic parameters in lumbar degenerative kyphosis: Correlation with spinal stenosis and spondylolisthesis

Study Design. Retrospective study. Objective. To define the relationship between pelvic parameters and lumbar spinal disorders including spinal stenosis, spondylolisthesis, and lumbar degenerative kyphosis (LDK). Summary Of Background Data. Although numerous studies have investigated the relationship between various lumbar spinal disorders and spinal parameters previously, none has reported on the relationship with LDK. Methods. The present study analyzed 211 patients (163 females and 48 males) with spinal stenosis (n = 57), degenerative spondylolisthesis (n = 78), spondylolytic spondylolisthesis (n = 34), and LDK (n = 42). Lateral standing radiograph of the whole spine was analyzed with a dedicated software allowing calculation of the following parameters: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), and sagittal vertical axis. Results. Significant differences in the pelvic parameter were observed between the groups. The mean PI in males (49.6°) was less than that in females (57.3°) (P < 0.05). PI was found to be proportional to SS, PT, and LL (P < 0.001). PT was inversely proportional to TK and LL (P < 0.001). Analysis revealed the values of SS, LL, and TK to be significantly higher and those of PT and the PT/PI ratio to be significantly lower in LDK than in the other groups. Values of PI, SS, and LL, but not PT, were significantly higher in subjects of LDK with Takemitsu type 1 than in those with type 2. PI was shown to possess statistically significant correlation to SS, PT, LL, and PT/PI ratio but not to TK or sagittal vertical axis. Conclusion. PI has a direct influence on the variable lumbar curvature in LDK. PI and SS may be complementary factors in determining the subtype of LDK, as PT appears to be relatively constant between the different subtypes of LDK.