How does the number of previous operations affect patient-rated outcome after surgery for lumbar spinal stenosis or lumbar disc herniation? A population-based cohort study from the Norwegian Registry for Spine Surgery

Abstract

Background: Several small, mainly single centre studies have linked repeated operations to inferior outcomes compared to primary operations after lumbar spine surgery. Few studies have specifically quantified the influence of previous operations on the outcome. Objectives: The aim of the study was to examine whether, and if so, to which extent the number of previous operations is associated with the outcome after surgery for lumbar spinal stenosis or lumbar disc herniation. Methods: This is a population-based study from the Norwegian Registry for Spine surgery (NORspine). The study included 26 723 cases operated for lumbar spinal stenosis or lumbar disc herniation in public or private Norwegian hospitals during the period 01.01.07 to 31.12.18. The primary outcome measure was Oswestry Disability Index (ODI). Secondary outcome measures were Numeric Rating Scale (NRS) score for back pain and leg pain, EuroQoL 5 Dimensions (EQ-5D), the Global Perceived Effect Scale (GPE) score, occurrence of perioperative complications and wound infections, and working capability. Binary logistic regression analysis was conducted to examine how the number of previous operations influenced the odds for not reaching a Patient Acceptable Symptom State (PASS). Results: The proportion achieving PASS (ODI raw score ≤ 22) decreased stepwise from 66.0 % in cases with no previous operation to 22.0 % in cases with four or more previous operations. The odds for not reaching PASS was doubled in cases with one previous operation, nearly tripled in cases with two previous operations and four to nearly seven times increased in cases with three or more previous operations. The ODI raw score and change score, the GPE and all the other secondary outcome measures showed trends with increasingly inferior outcomes with increasing number of previous operations. Conclusion: We found a dose-response relationship between increasing number of previous operations and inferior outcomes among patients operated for lumbar spinal stenosis or lumbar disc herniation. This information should be taken into consideration, along with other known predictors for favourable and unfavourable outcomes, in the shared decision-making process prior to surgery.