REVISION LUMBAR FUSIONS EXHIBIT WORSE CLINICAL OUTCOMES WHEN COMPARED WITH PRIMARY FUSIONS: A MATCHED COHORT ANALYSIS USING THE CANADIAN SPINE OUTCOMES AND RESEARCH NETWORK REGISTRY

The number of patients undergoing lumbar fusion procedures has increased by up to four-fold in the past twenty years.1,2 Revision lumbar fusions may be indicated for a variety of different pathologies including adjacent segment disease, recurrent stenosis or pseudarthrosis. Limited evidence is available regarding patient reported outcomes (PROMs) following revision lumbar fusions, however studies available would suggest worse clinical outcomes following revision lumbar fusions.3 This may confound by a variety of confounders including smoking and pre-operative comorbities.4 The aim of this study was to assess PROMs in patients undergoing revision lumbar fusions when compared to primary lumbar fusions. Patient data was collected from the Canadian Spine Outcomes Research Network database. Patients undergoing lumbar fusions were included. Patients under 18, undergoing surgery for infection, trauma, malignancy, deformity, concomitant cervical or thoracic spine surgery were excluded. Patients undergoing primary vs revision lumbar fusions were matched in a 1:1 ratio using propensity scores. Age, sex, diabetes, smoking status, ASA status and BMI were included in the propensity score model. Mean and standard deviations for ODI, EQ5D, SF-12 PCS, SF-12 MCS, VAS leg and back pain scores preoperatively, 6-18 weeks, 12 months post-operatively were compared using paired t-tests after matching. A total of 1,392 patients were included, with 696 patients in the primary and revision groups each. Patients in both cohorts demonstrated improvement in all PROMs. Patients undergoing revision lumbar fusions however experienced significantly less improvement in all PROMs when compared to their primary fusion counterparts. Despite this, clinical improvement following revision lumbar fusion meet the minimum clinically important difference thresholds for all PROMs. In a matched cohort model, patients undergoing revision lumbar fusions can expect less clinical improvement following surgery when compared to patients undergoing a primary lumbar fusion. They can, however, still obtain clinically meaningful gains following revision fusions. This study represents the largest to date assessing PROMs in patients undergoing revision lumbar fusions. Our results may be of use to spine surgeons counselling patients on expected outcomes following revision lumbar fusions.