PREDICTORS OF SPINAL SURGERY FOR PARTICIPANTS WITH NEUROGENIC CLAUDICATION: A SECONDARY ANALYSIS OF THE BETTER OUTCOMES FOR OLDER PEOPLE WITH SPINAL TROUBLE (BOOST) RANDOMIZED CONTROLLED TRIAL

Sources of Funding: This work is unfunded. LW, EW and SEL have been supported by the NIHR Exeter BRC, and LW is funded by the Bateman Professorial Fellowship. Conflicts of Interest: No conflicts of interest Purpose Neurogenic claudication (NC), caused by degenerative lumbar spinal stenosis, is the most common reason for older adults to undergo lumbar spinal surgery. This study aims to explore whether any participant characteristics are associated with conversion from conservative care to spinal surgery. Methods This was a secondary analysis of the Better Outcomes for Older People with Spinal Trouble (BOOST) randomised controlled trial (ISRCTN12698674), using a prognostic factor analysis. Baseline characteristics, including disability, walking confidence, pain intensity, walking capacity and radiological stenosis were analysed to identify predictors of conversion to surgery within 2 years post-randomisation. Multivariable mixed logistic regression was used to estimate adjusted odds ratios (AOR, 95%CI). Missing data were handled using multiple imputation by chained equations (50 datasets), pooled using Rubin's rules. Results Complete data were available for 294/435 participants (67.6%). Only 62/435 (14%) converted to surgery, with no differences between treatment arms. Multivariable analysis using imputed data (n=428) found baseline pain intensity had the strongest association [AOR 3.1 (95% CI 1.7 to 5.4)]. When including radiological variables, multilevel stenosis was additionally associated with surgical conversion (AOR 2.2; 95% CI 1.0 to 5.0). Six-month change scores were not associated with conversion. Conclusions A small proportion of participants undergoing conservative treatment for NC converted to surgery over two-years. Worse baseline pain and multi-level stenosis were associated with greater odds of surgical conversion. Clinicians should consider pain severity and radiological findings when managing patients with NC conservatively.