In vitro toxicity of local anaesthetics and corticosteroids on supraspinatus tenocyte viability and metabolism

BACKGROUND/OBJECTIVE: The purpose of this study was to evaluate supraspinatus tenocyte viability and metabolism in explants exposed to various local anaesthetics and corticosteroids. Our hypothesis was that the tendons exposed to these common injectates would have significantly decreased cell viability and metabolism compared with controls. METHODS: Supraspinatus tendon explants were obtained from dogs, placed in a culture media, and randomly assigned to one of the following groups: culture media only (control), 1% lidocaine, 0.5% lidocaine, 0.25% bupivacaine, 0.125% bupivacaine, 0.0625% bupivacaine, betamethasone acetate (5 mg), methylprednisolone acetate (40 mg), or triamcinolone acetonide (40 mg). Cell viability was determined on Days 1 and 7 after culture treatment using calcein AM (live cell) and Sytox Blue (dead cell) stains. Tissue metabolism was assessed on Days 1 and 7 using the resazurin blue metabolic assay. Significant differences were evaluated using a one-way analysis of variance with Tukey post hoc analysis. RESULTS: Compared with the controls, there were significant decreases in cell viability noted at Days 1 and 7 in tenocytes exposed to 1% lidocaine, betamethasone, and methylprednisolone. Significant decreases in cell metabolism were also noted at Days 1 and 7 in those groups. Treatment with 0.125% bupivacaine, 0.0625% bupivacaine, and triamcinolone demonstrated no decrease in cell viability or metabolism when compared with controls at any time point. CONCLUSION: This data confirms that peritendinous injection of commonly used local anaesthetics and corticosteroids results in significant supraspinatus tenotoxicity in vitro. Further in vivo studies are required before making definitive clinical recommendations.