Correlation of pelvic incidence with low- and high-grade isthmic spondylolisthesis.

PURPOSE

The development of isthmic spondylolisthesis is influenced by forces across the lumbosacral region of the spine. Pelvic incidence is a radiographic parameter that has been shown to be an independent parameter that influences both sagittal spinal balance and pelvic orientation. Our hypothesis then is that there is a positive correlation between pelvic incidence and spondylolisthesis.

STUDY DESIGN

A radiographic analysis of cases with spondylolisthesis.

OBJECTIVES

To try to assess the correlation between pelvic incidence in both low-grade and high-grade spondylolisthesis in both a pediatric and an adult population.

SUMMARY OF BACKGROUND DATA

The concept of pelvic incidence has been introduced into the literature. Its exact association with spondylolisthesis has not yet been clarified.

METHODS

Forty patients with spondylolisthesis were identified and divided into two groups: low-grade (Meyerding I-II) and high-grade (Meyerding III and higher). Radiographic parameters measured included lumbar sagittal alignment (T12-S1), sacral inclination, slip angle, and pelvic incidence. The spondylolisthesis was classified according to the Meyerding-Newman classifications and the slip angle. Radiographic measurements were also done in two control groups; there were 20 pediatric and 20 adult controls (mean age 11.8 years and 60.0 years, respectively). Unpaired t test analysis and Pearson correlation analysis were then done.

RESULTS

Mean pelvic incidence was 47.4 degrees in the pediatric control group, 57 degrees in the adult control group, 68.5 degrees in the low-grade isthmic spondylolisthesis group, and 79.0 degrees in the high-grade isthmic spondylolisthesis group. Pelvic incidence was found to be significantly higher in the high- and low-grade spondylolisthesis groups compared with both control groups (P = 0.0001). Pelvic incidence was significantly higher in the high-grade isthmic spondylolisthesis group than in the low-grade isthmic spondylolisthesis group (P = 0.007). A significant correlation existed between pelvic incidence and Meyerding-Newman scores (P = 0.03).

CONCLUSIONS

Pelvic incidence was significantly higher in patients with low- and high-grade isthmic spondylolisthesis as compared with controls and had significant correlation with the Meyerding-Newman grades (P = 0.03).