OPAL: a randomised, placebo-controlled trial of opioid analgesia for the reduction of pain severity in people with acute spinal pain-a statistical analysis plan

Low back and neck pain are a leading cause of disease burden globally. Opioids are recommended in guidelines for acute low back and neck pain; however, there is a lack of compelling efficacy data to support this. The OPAL trial is a prospectively registered, triple-blinded, randomised, placebo-controlled trial. Patients with acute (≤12 weeks duration) back and/or neck pain receive guideline care plus either an opioid (oxycodone + naloxone, up to 20 mg per day) or a placebo for up to 6 weeks or earlier, if pain is resolved. The primary outcome is pain measured using the Pain Severity Score of the Brief Pain Inventory with the primary time point being 6 weeks. Secondary outcomes include physical function, time to recovery, quality of life, adverse events and risk of opioid misuse. Outcomes are collected at weeks 2, 4, 6, 12, 26 and 52. Analysis will be done on an intention-to-treat principle. p values of