Sacralization of L5 in Radiological Studies of Degenerative Spondylolisthesis at L4-L5

STUDY DESIGN: Radiological analysis. PURPOSE: To investigate sacralization of L5 on radiological studies of degenerative spondylolisthesis at L4-L5. OVERVIEW OF LITERATURE: Degenerative spondylolisthesis commonly develops at L4-L5. Sacralization of L5 is thought to cause stress concentration at this level, which accentuates degenerative changes and promotes development of degenerative spondylolisthesis. However, there has been no study dedicated to determining whether the presence of sacralization at L5 influences the radiological findings in degenerative spondylolisthesis at L4-L5. METHODS: Seventy-eight patients with degenerative spondylolisthesis at L4-L5 were classified into two groups according to the presence of L5 sacralization: with (n=54) and without (n=24). Four radiographic parameters were measured and compared between the two groups: anterior slippage of L4 on L5 (% slip), facet orientation of L4-L5 (degrees), facet osteoarthritis of L4-L5 by Fujiwara's criteria (1~4 grades), and disc degeneration of L4-L5 by Frymoyer's criteria (grades 1~5). RESULTS: There was no significant difference in the degree of anterior slippage of L4 on L5 (17.02±6.21 versus 16.65±4.87, p=0.809), facet orientation (54.99±12.18 versus 56.23±4.35, p=0.642), facet osteoarthritis (3.43±0.59 versus 3.53±0.37, p=0.527), or disc degeneration (4.50±0.51 versus 4.35±0.61, p=0.340) between the two groups. CONCLUSIONS: Our study shows that the influence of sacralization of L5 on radiological findings in degenerative spondylolisthesis at L4-L5 may be less significant than previously expected. Further studies in large patient groups are needed to clarify the role of L5 sacralization on the development of degenerative spondylolisthesis at L4-L5.