The fate of adjacent segments with pre-existing degeneration after lumbar posterolateral fusion: the influence of degenerative grading.

Abstract

To evaluate the impact of pre-existing disc degeneration and its extent on future adjacent segment degeneration (ASDeg) after lumbar posterolateral fusion (PLF). A total of 102 patients who had undergone PLF for degenerative lumbar diseases from January 2006 to December 2008 were retrospectively reviewed by using radiography and clinical evaluation. The University of California at Los Angeles (UCLA) grading scale was used to evaluate the extent of disc degeneration. The Visual Analog Scale, Oswestry Disability Index, and SF-36 questionnaire were used to evaluate clinical outcomes. The overall prevalence of radiological ASDeg was 25.5 %, and the prevalence of ASDeg for the cranial and caudal levels was 19.6 and 15.1 %, respectively. The prevalence of ASDeg in one-, two-, and three-level fusion was 15.8, 26.3, and 50 %, respectively (p = 0.008). For the cranial level, the preoperative UCLA grade A, B, and C groups had prevalence values for ASDeg of 13.5, 28.6, and 42.9 %, respectively (p = 0.026). A higher prevalence of ASDeg was found in cranial discs with pre-existing degeneration than in the group without pre-existing degeneration (p = 0.012). The group without pre-existing degeneration showed better outcomes. For the caudal level, there was no significant difference in ASDeg prevalence. At final follow-up, the group without pre-existing disc degeneration showed better outcomes than the group with pre-existing disc degeneration. Adjacent segment discs with pre-existing degeneration had a higher likelihood of ASDeg progression compared with normal discs, especially for those classified as UCLA grade C.