PURPOSE OF THE STUDY Septic arthritis is an infection of joints caused by a pathogenic microorganism. Septic arthritis has a mortality rate of 11-40% when it's not treated properly. The mortality rate with methicillin-sensitive Staphylococcus aureus (MSSA)is 5-7%, while the rate with methicillin-resistant Staphylococcus aureus (MRSA)is 13-20%. The aim of this study is to evaluate the effects of intraarticular vancomycin and teicoplanin on joint cartilage in in vivo settings and its utility in routine MRSA treatment. MATERIALS AND METHODS In our study, 35 male Sprague-Dawley rats aged 28 days were used. Rats were obtained from the Regenerative and Restorative Medicine Research Center (REMER) of Istanbul Medipol University. Rats were randomly divided into 5 groups each containing 7 rats. Joint injections were administered with isoflurane analgesia every day at 6 am. Three rats (15 rats) from each group were sacrified in seventh day and evaluated immunohistologically to evaluate acute healing in articular cartilage. All remaining rats were sacrificed on day 28 and their knees were evaluated by immunohistochemical examination. RESULTS In our study, there were no complications in any rat during injection and the study period. Hematoxylin eosin (H & E) histological staining for evaluating cartilage healing and healing levels did not show statistically significant differences between the groups at first week (p > 0.05). Matrix metalloproteinase-13 (MMP-13) staining did not show any statistically significant difference between the groups. (p > 0.05). DISCUSSION MRSAseptic arthritis, diagnosed for the first time in 1960, has recently been responsible for 6-22% of all septic arthritis and is increasing day by day. The use of systemic vancomycin or teicoplanin is the first-line treatment method in MRSA septic arthritis. Serum levels reach the desired level, especially with intravenous infusion dose. On the other hand, it has been shown that intraarticular concentration does not reach a sufficient level in studies conducted. The use of intraarticular antibiotics during treatment can lead to more effective and early disease control by turning this negative situation into favor of the patient. As a result, intraarticular vancomycin and teicoplanin maximale tolerable and maintenance doses can be safely used beside surgery and intravenous antibiotics to increase efficacy of treatment, reduction of recurrence rates and reduction of mortality in MRSAseptic arthritis. CONCLUSIONS Intraarticular vancomycin and teicoplanin maximale tolerable and maintenance doses can be safely used beside surgery and intravenous antibiotics to increase efficacy of treatment, reduction of recurrence rates and reduction of mortality in MRSA septic arthritis. Key words:arthritis, infectious; methicillin-resistant Staphylococcus aureus; mortality.

Istanbul Medipol University Faculty of Medicine Department of Orthopedics and Traumatology Istanbul Turkey