Impact of Diluted and Undiluted Lidocaine and Ropivacaine on Chondrocyte Activity in Human Cartilage

• Naod Asres, Human Physiology, University of Delaware

• Xin Lu, Department of Mechanical Engineering, University of Delaware

Intra-articular injection of local anesthetics, such as lidocaine and ropivacaine, are commonly used during clinical procedures and to reduce postoperative pain. Dilution of these local anesthetics may be effective in reducing their potential chondrotoxic effects elicited in literature. The purpose of this study was to evaluate the effects of diluted and undiluted lidocaine and ropivacaine on chondrocyte activity in cartilage. Cartilage samples were harvested from osteoarthritic (OA) human cartilage. Samples were submerged in varying dilutions of media, saline, kenalog (TA), and either 1% lidocaine or 0.5% ropivacaine for their half lives, 90 and 110 minutes, respectively. Diluted lidocaine/ropivacaine groups were diluted with saline whereas undiluted lidocaine/ropivacaine groups weren’t, but both groups consisted of media and TA. Two control groups consisted of media and saline, one of which consisted of an additional quantity of kenalog. Chondrocyte viability was assessed 24 hours and 7 days after exposure, whereas ECM synthesis was assessed 72 hours after exposure. ECM synthesis was evaluated using a click chemistry method. In OA Human cartilage 24 hours after exposure, the top zone exposed to diluted lidocaine saw a significant decrease in viability, and undiluted lidocaine saw an additional  significant decrease compared to both control and diluted lidocaine groups. The middle zone only saw a significant decrease from undiluted lidocaine. Seven days after undiluted lidocaine exposure saw significant decreases in both top and middle zones. Both the top and middle zones of cartilage 24 hours after diluted ropivacaine exposure saw a significant decrease in viability, but no significant differences were found 7 days after exposure. ECM synthesis wasn’t significantly impacted by diluted lidocaine, diluted ropivacaine, or undiluted ropivacaine. These findings present insight into the chondrotoxic effect of lidocaine and ropivacaine that will better inform clinicians of the true effects of these local anesthetics.