Outcome of posterior lumbar interbody fusion for L4-L5 degenerative spondylolisthesis

Background: Posterior lumbar interbody fusion (PLIF) has become the standard in the treatment for degenerative spondylolisthesis since improvement of spinal instrumentation However, few published studies have reported long term outcomes of PLIF using a same surgical procedure. The purpose of this study is to evaluate a long term outcome of PLIF using a same surgical procedure for L4-L5 degenerative spondylolisthesis. Materials and Methods: Out of 45 patients who underwent L4-L5 PLIF for degenerative spondylolisthesis between 1995 and 2003, 37 patients (16 males and 21 females) were evaluated in this study. Mean age was 61.8 years. The average followup period was 121 months. We evaluated % slip, lordosis at L4/L5, lumbar lordosis, Japanese Orthopedic Association's (JOA) score and adjacent segment degeneration. Results: The % slip significantly improved from an average of 17.0% before surgery to 9.7% at the last followup. Lordosis at L4/L5 averaged 3.6 degrees before surgery, 8.2 degrees after surgery and 6.9 degrees at the last followup. Although patients experienced some loss of correction at last followup, their lordosis at L4/L5 at last followup still was significantly different from their lordosis at L4/L5 before surgery. Lumbar lordosis did not significantly change. Mean JOA score was 13.4 before surgery and 24.5 at the last followup; mean recovery ratio was 71.2%. Adjacent segment degeneration occurred in 40.5% of patients, almost all of which occurred in the cranial adjacent segment. Three patients (8.1%) required reoperation due to adjacent segment degeneration, at an average of 76 months after their initial surgery. Conclusions: With more than 10-year followup after L4-L5 PLIF for degenerative spondylolisthesis, the adjacent segment degeneration occurred in 40.5% and reoperation was required in 8.1%.