In Vitro Toxicity of Local Anesthetics and Corticosteroids on Chondrocyte and Synoviocyte Viability and Metabolism

OBJECTIVE: There is growing concern that intra-articular injection of local anesthetic and/or corticosteroids may cause significant morbidity, including potential toxicity to chondrocytes and synoviocytes, after even a single exposure. We demonstrate that full thickness canine chondral and synovial samples exposed to various local anesthetics and corticosteroids exhibit decreased loss of cell viability compared with prior in vitro studies using monolayer culture, due to the protective effects of intact extracellular matrix and cell heterogeneity. METHODS: Full-thickness cartilage and synovial explants were obtained from canine cadavers and exposed in culture media to the following for 24 hours: 1% lidocaine, 0.5% lidocaine, 0.25% bupivacaine, 0.125% bupvacaine, 0.0625% bupivacaine, betamethasone acetate, methylprednisolone acetate, triamcinolone acetonide, or culture media only (control). Cell viability was determined on days 1 and 7 of culture using a microscopic live-dead and alamar blue metabolic assays. RESULTS: Complete loss of chondrocyte and synoviocyte viability was noted in the 1% and 0.5% lidocaine group, 0.25% and 0.125% bupivacaine group, betamethasone group, and methylprednisolone groups after 1 and 7 days of culture. Treatment with 0.0625% bupivacaine and triamcinolone demonstrated no decrease in cell viability or metabolism when compared to negative control. CONCLUSIONS: In this canine explant model, 1% and 0.5% lidocaine, 0.25% and 0.125% bupivacaine, betamethasone acetate, and methylpresdnisolone acetate were severely chondrotoxic and synoviotoxic after a single exposure, despite intact extracellular matrix. In contrast, chondrocytes and synoviocytes exposed to 0.0625% bupivacaine and triamcinolone remained viable after treatment. Further in vivo study is needed before definitive recommendations can be made.