Magnetic resonance imaging 20 years after anterior lumbar interbody fusion

Study Design. A 20-year magnetic resonance imaging (MRI) and functional outcome follow-up study was performed on patients who had undergone anterior lumbar interbody fusion. Objectives. The objectives of the present study are to determine whether or not degeneration is related to adjacent level fusion and the clinical significance of this degeneration. Summary of Background Data. There are concerns that lumbar fusion leads to increase stress at the adjacent levels. However, the clinical significance of this remains unclear. Methods. Thirty-nine patients who underwent lower lumbar anterior lumbar interbody fusion and who had normal preoperative discograms at the level adjacent level were evaluated with a minimum of a 20-year follow-up. MRI scans were performed and independently evaluated for any evidence of degeneration. Functional status was assessed using the Low Back Outcome Scale. Results. Twenty-nine (74.3%) patients had some evidence of degeneration in their lumbar spine and advanced degeneration was identified in 12 (30.7%) patients. Nine (23.1%) patients had advanced degeneration isolated to the adjacent level and 7 (17.9%) patients had evidence of advanced degeneration with preservation at the level adjacent to the fusion. There was no association between function and radiographic degeneration. Only 3 patients required additional surgery as a result of adjacent level degeneration. Conclusion. The prevalence of degenerative changes is similar to other studies involving normal asymptomatic subjects. Furthermore, the majority of degenerative changes seen occurred over multiple levels or at levels not adjacent to the fusion, suggesting that changes seen may be more likely related to constitutional factors as opposed to the increased stresses arising from the original fusion.