Minimum effective dose of betamethasone for incisional local infiltration for the prevention of postoperative pain after spine surgery: study protocol for a randomised controlled trial.

introductionPostoperative pain is particularly pronounced in spinal surgery. Inadequate management of acute postoperative pain not only reduces patient satisfaction and delays recovery but also increases the risk of developing chronic pain. Local infiltration analgesia (LIA) is a widely used technique for perioperative pain management. However, even with the use of long-acting local anaesthetics, such as ropivacaine, postoperative analgesia often remains insufficient. Preliminary evidence suggests that combining diprospan, a mixture of betamethasone disodium phosphate and betamethasone dipropionate, with ropivacaine can significantly reduce analgesic requirements in the immediate postoperative period. However, concerns about steroid-related complications, including hyperglycaemia and surgical site infections, highlight the need to identify the minimum diprospan concentration to achieve a balance between efficacy and safety. This randomised, controlled, evaluator-blinded trial aims to investigate the dose-response relationship of diprospan as an adjunct to ropivacaine for LIA in spinal surgery to determine the minimum effective dose for effective and safe pain management. METHODS AND ANALYSIS: This is a single-centre, randomised, evaluator-blinded, controlled, dose-mapping study in which subjects will be randomised in a 1:1:1:1:1 ratio to the control group or to receive diprospan at concentrations of 0.003%, 0.006%, 0.009% or 0.012%. Patients will receive either 0.5% ropivacaine alone or a corresponding dose of diprospan combined with 0.5% ropivacaine for LIA. All participants will be followed for a duration of 3 months. The primary outcome measure will be cumulative sufentanil consumption within the first 48 hours postsurgery. Secondary outcomes will include additional assessments of analgesia, steroid-related adverse events and other complications within the 3-month follow-up period. ETHICS AND DISSEMINATION: This study protocol was approved by the Institutional Review Board of Beijing Tiantan Hospital (KY2024-365-02-1). Written informed consent will be obtained from all participants. The results will be submitted for publication in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: NCT06785350.