Intra-articular application of local anesthetics is a common procedure in clinical medicine. It was considered safe until the first reports of unusual acute postoperative degeneration and degradation of articular cartilage, so called chondrolysis, emerged in the literature. Chondrolysis was typically occurring after arthroscopic surgery followed by postoperative pain management with continuous infusion of local anesthetics. Based on those reports, many in vitro studies showed harmful effect of local anesthetics on the articular cartilage. Even short term exposure caused chondrocyte dysfunction and death. As there are no known reports on chondrolysis after knee arthroscopy in local anesthesia or after single intra-articular injection for pain management, we hypothesized that certain chondroprotective factors exist in the natural environment, that protect articular cartilage from toxic effect caused by local anesthetics. Presented thesis was designed as four interconnecting experiments combining in vivo clinical data and in vitro laboratory simulations with intention to show that clinical use of single application of local anesthetic for knee arthroscopy or single analgesic injection have no harmful effect on the articular cartilage of the knee.
1) Data of 49 patients that were treated for isolated cartilage lesions in the knee with autologous chondrocyte implantation were retrospectively analyzed. Bioptic samples of cartilage were harvested from their knees with arthroscopy under general, spinal, and local anesthesia. The three anesthesia groups were compared for cell viability, population doublings, and chondrocyte morphologic properties in biopsies and also in cell cultures. 2) Intra-articular concentration of lidocaine was determined in 10 patients during knee arthroscopy in local anesthesia. They received an intra-articular injection/infiltration of 2% lidocaine ten to fifteen minutes prior to the procedure. With the introduction of the arthroscope, joint liquid samples were aspirated and then analyzed for the concentration of lidocaine with mass spectrometry. 3) 27 osteochondral explants were harvested from the healthy knees of 10 donors during forensic autopsies. The explants were incubated for different time intervals (30 min, 2h and 24h) in standard 2% concentration of lidocaine, in the concentration measured in the second subexperiment of the study (0.04%) and in the cell culture medium (control). The differences in viability of chondrocytes among groups were evaluated on confocal laser microscope. 4) The effect of lidocaine on degenerated cartilage was determined in osteoarthritic knees. 10 patients scheduled for total knee replacement received an intra-articular injection of 2% lidocaine 10 to 15 minutes prior to the procedure. During surgery, osteochondral explants were harvested and analyzed for the viability of chondrocytes under confocal laser microscope. The results were compared to control group of 9 patients without preoperative lidocaine injection.
1) No differences in cell viability, growth potential, and morphology of cells in cartilage biopsies and chondrocyte cell cultures among different types of anesthesia were found. 2) The concentration of lidocaine in knee aspirates was significantly lower than the original concentration infiltrated in the knee (on average 225 mg/ml, 0,02%); it was also lower than we would expect solely on the basis of volume distribution. 3) In vitro short term exposure to the reduced concentration of lidocaine had no influence on chondrocyte viability in healthy cartilage explants. 4) Viability of chondrocytes in degenerated cartilage in the knees treated with preoperative 2% lidocaine injection was not significantly reduced in comparison to the control group.
None of the subexperiments of this study demonstrated a harmful effect of single intra-articular knee administration of lidocaine or short term exposure to lidocaine on articular cartilage of the knee. According to our results there are intra-articular mechanisms present that diminish local anesthetic toxicity to the cartilage in the physiologic conditions. The most important factors appear to be a significant reduction of local anesthetic concentration shortly after its intra-articular application and limited penetration of local anesthetic through the intact superficial cartilage layers.