Correlation of Pelvic Parameters with Isthmic Spondylolisthesis

STUDY DESIGN: A retrospective radiological evaluation. PURPOSE: To verify that PI is related with progression of IS as well as development of IS and to assess the differences of pelvic parameters between the L4 & L5 IS, as well as between single & two level IS. OVERVIEW OF LITERATURE: High pelvic incidence (PI) has been known to be related with development of IS. However, the previous studies were limited to just L5 spondylolisthesis or there was no differentiation between L4 & L5 spondylolisthesis METHODS: Sixty five IS patients and 30 persons as a control group participated the study. Among the 65 patients, 30 had L4 IS, 30 had L5 IS and 5 had bi-level IS. We used the whole spine lateral radiographs to measure the slip percentage, the pelvic tilt (PT) and the pelvic incidence (PI), and we compared them between the normal control group and the IS patients, as well as between single-level and bi-level spondylolisthesis, and we investigated the correlation between the degree of slip of spondylolisthesis and the pelvic parameters. RESULTS: The averages of the PT, PI and lumbar lordosis (LL) in the control group and the IS group were 11.0° vs 21.4° (p<0.001), 49.1° vs 61.8° (p<0.001) and 48.5° vs 57.6° (p<0.001), respectively. On comparison between the L4 and L5 IS groups, there was no difference in all the pelvic parameters (p>0.05). On comparison between the single-level IS group and the bilevel IS group, there was a significant difference of the PT and PI (p<0.05), and the slip percentage had a correlation with only the PI among all the pelvic parameters (Spearman's r=0.293, p=0.023). There was a significant correlation of the degree of slip with the PI for the L5 single level IS, but not with the L4 single level IS (r=0.362, p=0.05). CONCLUSIONS: The high pelvic incidence can be a factor of L4 & L5 spondylolysis and it may have an influence on the slip progression in patients with L5 isthmic spondylolisthesis, but not on the slip progression in patients with L4 IS. Yet other factors seem to have an influence on the slip progression in patients with L4 isthmic spondylolisthesis.