A Comparative Study of the Floating L4-5) vs Lumbosacral L4-S1) Spinal Fusions

Kim, Hong Tae; Park, Bong Hoon; Cheon, Dong Wook; An, Hyug Su; Lee, Hyung Seok

Abstract

In cases of L4-5 spinal fusions, L5-S1 segment used to be included in the fusion traditionally for fear of progressive deterioration of the lumbosacral motion segment after fusion above. The purpose of this study was to evaluate the advisability of extension to L5-S1 segment in cases of L4-5 fusion for an isolated pathologic condition in L4-5 sement. A retrospective review of 72 patients with spinal fusion for an isolated pathologic condition in L4-5 segment was undertaken to compare the clinical results and adverse effects in two groups. One group consisted of 39 patients with floating L4-5 fusion(SF), and the other group consisted of 33 patients with L4-S1 fusion(LSF). The age, pathologic condition at L4-5, and the fusion method(lateral fusion) were matched in two groups. The mean follow-up period was 43.6 months(ranging 24-69 months). Comparisons were made for operative problems, post-operative complications, the amount of changes in angular motion at the adjacent segments to fusion at the last follow-up compared to the pre-operative motion, and the clinical results of treatment. The LSF group took 38 more minutes and lost 245 grams of more blood in averages to complete the additional surgical procedures compared with those in SF group. Several considerable post-operative complications were one deep infection in SF group and three metal failures of sacral fixation with subsequent two fusion failures in LSF group which were mostly concerned with the sacral fixations. The changes of angular motion at follow up compared to pre-operative motion in SF group were 1.5° gain in average (ranging 3° loss-6° gain) in L3-4 segment and 0.6° gain in average (ranging 5° loss-5° gain) in the L5-S1 segment. Those in L3-4 segment of LSF were 2.8° gain in average (ranging 2°-loss 9° gain). Therefore the higher stress and subsequent degeneration are more likely expected above the L4-S1 fusion rather than below the L4-5 fusion. The satisfactory clinical results were 89.7% in SF group and 87.9% in LSF group without significant difference between two groups. In conclusion there is no need to include the L5-S1 segment in the L4-5 fusion when the pathology is limited to L4-5 segment.