Does Fusion Status Correlate with Patient Outcomes in Lumbar Spinal Fusion?

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Study Design. Prospective cohort. Objectives. The purpose of this study is to examine the relationship between radiographic fusion and patient-reported health-related quality of life (HRQOL) measures in patients undergoing instrumented posterolateral lumbar fusion. Summary of Background Data. Previous studies have shown that a solid fusion does not always produce clinical success. However, these studies did not use validated patient-reported HRQOL measures. Methods. One hundred ninety-three patients who underwent instrumented posterolateral fusion with complete preoperative and 2-year HRQOL measures and a fine-cut computed tomographic (CT) scan with reconstructions done at 2 years after surgery specifically done to assess fusion status were identified. HRQOL measures included the Oswestry Disability Index (ODI), the Short Form-36 and back and leg pain numerical rating scales. The percentage of patients reaching the minimum clinically important difference and substantial clinical benefit for ODI and Short Form-36 were also calculated. CT scans were graded as fused or not by three independent reviewers. Comparisons were made in outcomes measures between the patients with solid fusions and those judged not to have a solid radiographic fusion. Results. There were 124 women and 69 men with an average age of 63 years. Patients judged to have a solid fusion demonstrated a better ODI score at 2 years than those who were not solidly fused (P = 0.023). There was a trend toward greater improvement in mean ODI score in those with a solid fusion (P = 0.074). A statistically greater number of patients who had a solid fusion (111 of 171, 65%) achieved the minimum clinically important difference for ODI than those who did not achieve a solid fusion (7 of 22, 32%) (P = 0.004). Conclusion. A greater proportion of patients achieved clinically relevant improvements in low back specific quality-of-life measures when they had achieved a solid fusion than patients who did not have a solid fusion. Although radiographic fusion may not be the true measure of clinical success, this study suggests that solid arthrodesis contributes to clinical outcome and is an important goal of fusion surgery.