Complications and Outcomes in Patients with Inflammatory Arthritis Following Minimally Invasive Lumbar Fusion

Introduction: Patients with inflammatory arthritis are at special risk of developing spinal pathology. There is a paucity of literature investigating outcomes following minimally invasive lumbar fusion in patients with inflammatory arthritis. The aim of this study was to compare 90-day complication rates and clinical outcomes in patients undergoing minimally invasive lumbar fusion with and without inflammatory arthritis.

Methods: Patients who had undergone minimally invasive fusion between 2017 and 2023 for the treatment of degenerative pathology of the lumbar spine with a minimum of six months follow-up were included and separated into inflammatory arthritis (IA) or non-inflammatory arthritis (non-IA) cohorts. Patient demographics, perioperative variables, 90-day complications, patient-reported outcome measures, and rates of MCID achievement were compared between the IA cohort and the unmatched and 3:1 case-control matched non-IA cohorts at early ( < 6 months) and late (≥6 months) follow-up.

Results: Six hundred sixty-nine patients were included (IA cohort, n=23; Non-IA cohort, n=646). Patient demographics and perioperative characteristics did not differ significantly between the two cohorts except for IA patients reporting a higher age-adjusted Charlson Comorbidity Index (p=0.004). There were no significant differences in 90-day complications, reoperations, or readmissions. The IA cohort demonstrated significant improvements in most PROMs at the early and late postoperative time points. PROM scores, magnitudes of improvement in PROMs, MCID achievement rates, and time to achieve MCID for most PROMs were not significantly different between the two cohorts. After 3:1 case-control matching, there were no significant differences in complications, reoperations or admissions. Additionally, there were no significant differences between the two cohorts in most PROMs scores or rates of MCID achievement. Magnitudes of improvement and time to achieve MCID were comparable between the two cohorts for all PROMs.

Conclusion : The findings of this study suggest that clinical outcomes following minimally invasive lumbar fusion are similar in IA patients as compared to both a matched and unmatched non-IA control cohort. This patient population may have an even larger marginal benefit from soft tissue sparing principles of minimally invasive surgery, and it is a technique that should be considered for their treatment in the future.