The Long Term Effect of Posterolateral Fusion in Adult Isthmic Spondylolisthesis

Background: Today there is some evidence based medicine support for a positive short term treatment effect of fusion in spondylolisthesis with chronic low back pain with or without sciatica. The long term effect is, however, unknown.

Purpose: To determine the long term outcome of lumbar fusion in adult isthmic spondylolisthesis.

Study Design: Prospective, randomized controlled study comparing a one year exercise program with instrumented and non-instrumented posterolateral fusion with average long term follow-up of 9 years (range 5- 13 years).

Methods: 111 patients aged 18-55 years with adult lumbar isthmic spondylolisthesis at L5 or L4 level of all degrees, and at least one year duration of severe lumbar pain with or without sciatica were randomly allocated to treatment with 1. a one year exercise program (n=34), 2. posterolateral fusion without pedicle screw instrumentation (n=37), or 3. posterolateral fusion with pedicle screw instrumentation (n=40). Pain and functional disability was quantified by pain (VAS), the Disability Rating Index (DRI), the Oswestry Disability Index (ODI) work status, and global assessment of outcome by the patient into much better, better, unchanged or worse. Quality of life was assessed by the SF-36. Long term follow-up was obtained in 89% of patients. 9 patients in the exercise group were eventually operated on.

Results: Longitudinal analysis: At long term follow up pain and functional disability was significantly better than before treatment in both surgical groups. There were no significant differences between instrumented and non-instrumented patients in any variable studied. In the exercise group the pain was significantly reduced, but not the functional disability. Compared to the 2 year follow up there was a significant increase in functional disability, as measured by the DRI, but not the ODI, in the surgical group at long term. In the exercise group there were no significant changes between the 2-year and the long term follow-up. Cross-sectional analysis: Between the surgical and conservative group there were no significant differences in any outcome measurement at long term follow-up except for global assessment, which was significantly better for patients operated on. 76% of patients operated on classified the overall outcome as much better or better compared to 50% of conservatively treated patients (p=0.015). Quality of life as estimated by the SF-36 at long term was not different between treatment groups in any of the 8 domains studied, but considerably lower than for the normal population.

Conclusions: Posterolateral fusion in adult lumbar isthmic spondylolisthesis results in a modestly improved long term outcome compared to a 1-year exercise program. Although the results show that some of the previously reported short term improvement is lost at long term, fused patients still classify their global outcome as clearly better than conservatively treated patients. Furthermore, since the long term outcome of the conservatively treated patients most likely reflect the natural course, one can also conclude that no major spontaneous improvement should be expected over time in adult patients with symptomatic isthmic spondylolisthesis. In most patients substantial pain, functional disability and a reduced quality of life will remain unaltered over many years.