A Modified Method to Treat Severe Asymptomatic Pre-existing Degeneration of Adjacent Segment: A Retrospective Case-Control Study

Background: Pre-existing degeneration of adjacent segment is an important risk factor for adjacent segment degeneration (ASD), but limited and controversial studies have addressed its management. Methods: Patients with symptomatic degeneration of the L5/S1 segment warranting surgical interference and severe asymptomatic degeneration of the L4/5 segment were retrospectively analyzed. Among them, those who underwent interbody fusion in the causative (L5/S1) segment and distraction of the intervertebral space and facet fusion in the adjacent L4/5 segment were included as Group A (n=103). Patients who underwent interbody fusion in both L5/S1 and L4/5 segments were included as Group B (n=81). Clinical and radiographic outcomes were evaluated. Results: Mean follow-up was 58.5 months (range, 48-75 m). No significant difference in clinical outcomes or the incidence of adjacent segment degeneration in L3/4 segment was found between Groups A and B. Compared with Group B, less bleeding (315±84 vs. 532±105 ml), shorter operation time (107±34 vs. 158±55 min) and lower costs (13,830±2640 vs. 16,020±3380 US$) were found in Group A ( P <0.05). In Group A, disc height ratio (DHR) of L4/5 segment was significantly increased from preoperative value of 0.40±0.13 to last follow-up value of 0.53±0.18 ( P <0.05), while the degree of canal stenosis (DCS) was decreased from preoperative value of 34.3±11.2% to last follow-up value of 15.9±9.3% ( P <0.05). Conclusions: This modified method could be effective in treating severe asymptomatic pre-existing degeneration of adjacent segment in lumbar spine.