Exploring Bias Patterns in Systematic Reviews and Meta-Analyses of Bone Marrow Aspirate Concentrate

INTRODUCTION: Bone marrow aspirate concentrate (BMAC) is increasingly used in orthopaedics for its regenerative potential. As clinicians rely on systematic reviews and meta-analyses to guide clinical decision making, concerns remain regarding methodologic rigor and reporting bias (spin). This study evaluated the prevalence and types of spin within systematic reviews and meta-analyses investigating the use of BMAC and assessed study quality using the AMSTAR 2 tool. METHODS: A systematic search of PubMed, Scopus, and EMBASE was conducted in May 2025 per Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Eligible studies were systematic reviews or meta-analyses of BMAC in clinical orthopaedic contexts. Each study was assessed for 15 predefined spin types grouped as misleading interpretation, misleading reporting, or inappropriate extrapolation. Methodologic quality was appraised using AMSTAR 2. Associations between study characteristics and spin were analyzed using t-tests, analysis of variance, Fisher test, and Spearman correlation. RESULTS: Of the 156 studies screened, 28 met inclusion criteria. Spin was identified in 21 abstracts (75.0%), with the most frequent types being selective reporting of outcomes (type 3, 64.3%), claims of benefit despite high risk of bias (type 5, 53.6%), and selective emphasis on notable outcomes (type 11, 50.0%). Across spin categories, misleading interpretation was most common (67.9%). AMSTAR 2 rated 67.9% of studies as critically low confidence, 17.9% as low, and only 7.1% as high confidence. No notable association was found between spin prevalence and publication year, level of evidence, or journal impact factor. CONCLUSION: Most review studies on BMAC demonstrated low methodologic quality and frequent use of spin, with three spin types accounting for the most reporting bias. These findings suggest a consistent overstatement of BMAC efficacy and highlight the need for improved transparency, adherence to reporting standards, and rigorous methodology in future reviews to better inform clinical decision making. LEVEL OF EVIDENCE: IV.