MAGNETIC-RESONANCE-IMAGING ASSESSMENT OF DISC DEGENERATION 10 YEARS AFTER ANTERIOR LUMBAR INTERBODY FUSION

Study Design. One-hundred-eight patients from a consecutive series of 125 anterior lumbar interbody fusions were invited to participate in a radiographic and magnetic resonance imaging assessment more than 10 years after the original surgery. Objective. The aim of this study was to determine the long-term incidence of disc degeneration adjacent to an anterior interbody fusion and to determine whether this was influenced by the length of the fusion. Summary of Background Data. Biomechanical studies in human cadaver spines support the view that fusion in the lumbar spine is likely to be associated with an increased incidence of degeneration at adjacent levels, but there is little reliable information on the incidence of juxtafusion degeneration from the few long-term studies of lumbar spine fusion reported in the literature. Methods. Eighty-seven patients agreed to take part in the study, but in six cases the magnetic resonance imaging procedure had to be abandoned. Of the 81 patients who underwent both radiographic assessment and magnetic resonance imaging scanning, preoperative discography had demonstrated a normal disc above the level of the fusion in 52. This group of patients formed the basis of this report. Each sequence of magnetic resonance imaging films was examined by one radiologist. The signal strength was assessed on T-2-weighted images in the sagittal plane and disc morphology was assessed on T-1- and T-2-weighted sagittal and T-1-weighted axial images. Fusion status was assessed on the plain films and magnetic resonance imaging. Results. The incidence of a normal adjacent intervertebral disc in cases of solid fusions to the sacrum was 68%. This was not influenced by the length of the fusion. Conclusion. The findings of this study suggest that degeneration after an anterior lumbar interbody fusion is determined more by individual characteristics than by the fusion itself.