Higher Risk of Adjacent Segment Degeneration After Floating Fusions: Long-Term Outcome After Low Lumbar Spine Fusions

STUDY DESIGN: We report the long-term outcome after mono-segmental and bisegmental fusions at the lumbar L4-S1 region of the spine. OBJECTIVE: Long-term clinical and radiologic outcome measures were used to determine a lumbar fusion's contribution to degenerative changes in adjacent motion segments (ASD). SUMMARY OF BACKGROUND DATA: The role of low lumbar spinal fusions and their long-term contribution to accelerated degenerative changes in the adjacent motion segments continues to be a subject of controversy. PATIENTS AND METHODS: We followed-up 102 patients with an average age of 54 (22 to 78) years and a follow-up time of 14 (3 to 22) years. RESULTS: Overall results in patients were good, the Oswestry-Disability Index (ODI) showed an average of 26% (0% to 70%) at follow-up, the Visual Analog Scale rose from 2.7 (postoperative) and 2.9 (12 wk follow-up) to 3.6 (latest follow-up) points, respectively. Patient satisfaction with their health-related situation at follow-up was 69% (15% to 100%). Patients who underwent fusions of the segment L5/S1 showed a significant (P<0.05) lower risk for ASD than patients with fusions L4/5 (20% vs. 46%). Compared with L4/5 fusions, bisegmental L4-S1 fusions showed a similar trend (P=0.06) with a lower risk for ASD (24%). Objective and subjective clinical results showed no differences between these groups. Patients suffering from ASD showed significant (P<0.05) reduced sacral inclination and lumbar lordosis angles and also significant (P<0.05) higher ODI values compared with non-ASD patients. CONCLUSIONS: We conclude that floating fusions of single low lumbar segments are more likely to result in ASD and are negatively influenced by sagittal plane abnormalities.