Does Disc Space Height of Fused Segment Affect Adjacent Disc Degeneration in Anterior Lumbar Interbody Fusion? A Radiological Study

Background: The restoration of disc space height (DSH) is essential in anterior lumbar interbody fusion (ALIF), while it is unclear whether the reduction of DSH may alter the mechanical status and adversely affect adjacent segment, and few literatures focused on the subject. Methods: Ninety five patients who had undergone ALIF for degenerative disc disease at our institution between March 2004 and March 2007 were retrospectively reviewed and 76 patients were enrolled in this study. Preoperative, postoperative and the final follow-up segmental lordosis (SL), whole lumbar lordosis (WLL) and DSH were measured and compared in adjacent segmental degeneration (ASD) group and non-ASD group, and the relationship between DSH, SL, WLL and ASD were investigated retrospectively. Results: In 76 patients, the radiographic ASD was proven in 25 (32.9%) and symptomatic ASD in 2 patients. There was a significant correlation between DSH and SL, but was insignificant between DSH and WLL, and a significant correlation was noticed between ASD and SL, WLL and DSH at final follow-up. Conclusion: The normal DSH and SL is important for preventing ASD and an anterior cage with appropriate height and lordotic angle to be used in ALIF to maintain the proper DSH and SL.