The In Vivo Chondrotoxicity of Single Intra-articular Injection of Local Anesthetic in Rat Cartilage

Introduction A constant infusion of local anesthetics through pain pumps has been shown to cause chondrolysis. However, there is no general consensus regarding the safety of a single intra-articular injection of local anesthetics. In this experimental study, we examined the rat cartilage for possible histological effects after a single intra-articular administration of lidocaine or ropivacaine. Material and methods Thirty-two male Sprague-Dawley rats, weighing 250-300 grams, were divided into two groups of 16 each. We injected 0.1 ml of either lidocaine 2% (20 mg/ml) or ropivacaine 0.75% (7.5 mg/ml) into the left knee of the rats. The right knee in both groups was used as a control, and an equal amount of normal saline was injected. Each group was further divided into subgroups of four, which were euthanized after one, seven, 21, and 60 days after the initial injection. Knees were excised and prepared for histopathological analysis. A modified version of the Mankin score was used for cartilage damage evaluation. Results No difference regarding cartilage damage was detected after the examination under light microscopy between lidocaine, ropivacaine, and placebo in all specimens. Time elapsed since the initial injection did not affect the results at any time point. Conclusion A single intra-articular injection of local anesthetic did not induce any histological changes in the rat cartilage. Further research is needed to demonstrate the safety of humans.