Lost in submission? Investigating publication bias in regional anaesthesia: a pilot case study of the erector spinae plane block

Background: The Erector Spinae Plane (ESP) block is a regional anaesthesia technique with a growing range of clinical applications due to its short learning curve, low complication rate, and effectiveness. However, publication bias can distort the perceived efficacy of interventions, especially when studies with negative or inconclusive results remain unpublished. The real extent of publication bias in ESP-related clinical research currently remains unclear. Methods: We searched ClinicalTrials.gov on 2 February 2025 using the terms Erector Spinae Plane Block and ESP block, and obtained 671 records. After excluding duplicates, irrelevant, and ongoing studies, 500 records were eventually included. Study characteristics and publication status were determined using a multi-step search strategy that included PubMed, Scopus, Embase, and Central. Data were analysed using appropriate statistical tests on R (v3.4.0). Results: Of the 500 studies included, 361 (72.2%) were complete, 102 (20.4%) had unknown status, and 37 (7.4%) had been suspended, terminated, or withdrawn. Only 211 studies (42.2%) were published, and included data from 14374 of 32,600 intended patients. Published studies were registered significantly earlier than unpublished ones (median year 2020 vs 2021; P=.004). No significant differences were found between published and unpublished studies in terms of main outcome, continent, surgical setting, study design, or sample size. Conclusions: A substantial proportion of ESP block studies remain unpublished, indicating potential publication bias. Although earlier registration was associated with publication, other study characteristics were not. These findings highlight the need for increased transparency and for clinical trial results to be published regardless of outcome in order to ensure that the evidence base is unbiased.