In Vivo Toxicity of Local Anesthetics and Corticosteroids on Supraspinatus Tenocyte Cell Viability and Metabolism.

Background: This study was conducted to evaluate the effects of commonly used injection medication combinations on supraspinatus tenocyte cell viability and tissue metabolism.

Methods: Twenty adult dogs underwent ultrasound guided injection of the canine equivalent of the subacromial space, based on random assignment to one of four treatment groups (n=5/group): normal saline, 1.0% lidocaine/methylprednisolone, 1.0% lidocaine/triamcinolone or 0.0625% bupivacaine/triamcinolone. Full-thickness sections of supraspinatus tendon were harvested under aseptic conditions and evaluated on days 1 and 7 post-harvest for cell viability and tissue metabolism. Data were analyzed for significant differences among groups.

Results: Tendons exposed to 1% lidocaine/ methylprednisolone had significantly lower cell viability at day 1 as compared to all other groups and control. All local anesthetic/ corticosteroid combination groups had decreased cell viability at day 7 when compared to the control group.

Conclusions: This study demonstrated significant in vivo supraspinatus tenotoxicity following a single injection of combination local anesthetic/ corticosteroid when compared to saline controls.

Level of Evidence: Level II.