Outcome of one-level posterior lumbar interbody fusion for spondylolisthesis and postoperative intervertebral disc degeneration adjacent to the fusion

Study Design. Review of the clinical and radiologic records of patients who underwent one-level posterior lumbar interbody fusion (PLIF) at L4-L5. Objective. To determine whether adjacent intervertebral disc degeneration after PLIF affects the clinical results, and whether preoperative caudal disc (L5-S1) degeneration affects postoperative clinical results. Summary of Background Data. There is little reliable information in the literature regarding clinical results and adjacent disc degeneration after PLIF. Methods. Forty-five patients who underwent L4-L5 PLIF for spondylolisthesis with more than 5 years of postoperative observation were included in this study. PLIF was performed in conjunction with posterior instrumentation. The posterior lumbar intervertebral grafting was performed using both autograft and a ceramic spacer. Intervertebral disc heights at L2-L3, L3-L4, and L5-S1 were measured before and after surgery. The patients were divided into two groups based on the presence or absence of the preoperative L5-S1 narrowing. Correlation between clinical status evaluated by the recovery rate of the Japanese Orthopedic Association (JOA) score and disc heights were determined. Results. All intervertebral disc heights adjacent to the fusion decreased after surgery (P < 0.05). However, no significant correlation was seen between clinical results estimated by the recovery rate and postoperative disc narrowing. There was also no significant difference in clinical results between patients with or without preoperative L5-S1 narrowing. Conclusions. There is no evidence from the results that postoperative narrowing of the adjacent disc and preoperative narrowing of the L5-S1 disc affects the clinical outcome of L4-L5 PLIF.