This is a retrospective analysis of an 11-year experience of a single knee surgeon from a referral knee center and a total of 2024 consecutive primary TKAs were enrolled. Patients include those from all over Iran. Intrawound vancomycin powder was used in 1710 cases and the results were compared with a historical control group with 314 cases. The mean age, mean duration of surgery and mean Length of stay along with data on comorbidities and final outcome of those who were diagnosed to have superficial or deep infections are presented.
The mean length of stay in our study was 3.21 days (SD=2.05), which is somewhat higher than recent reports (25, 26). In our center, preoperative planning and paraclinical work-ups of patients were performed on an outpatient basis. Only after determining precise surgical plans, having prepared required devices, and optimizing their medical states, were TKA candidates scheduled for surgery. Patients were admitted to the hospital early in the morning and then underwent surgery the same day and if alert and well, patients were discharged the next morning. The only exceptions were those patients coming from distant cities or rural places of the country who neither had a place to stay in Tehran nor could come back any time sooner than 2 months after surgery. Since a strong family physician-based postop care system is not available in Iran, this small group of patients were discharged after 1 to 2 weeks, until knee range of motion was secured and the surgical wound completely healed. Of our TKAs, 90% were discharged in less than 6 days and 60% were discharged in less than 3 days after surgery.
Mean age in our study population was 65.20 (SD=10.83), which is somewhat younger than that of similar studies (22), despite the fact that people here refer for surgery at the latest stages of knee joint destruction. This obvious lower age of TKA candidates in Iran could be due to the Middle-eastern lifestyle which is characterized by high-flexion activities such as praying, sitting on the ground and using Iranian toilets which need squatting.
Previously it has been proved that increased operative time could result in higher complication rate especially infection, venous thromboembolism (VTE) and patient dissatisfaction (25, 27-32). Each TKA surgery took an average of 60.30 minutes (SD= 44.19) from incision to wound dressing, which is comparable to other reports (28, 33).
In the vancomycin group, there were 32 cases (1.87%) of suspected superficial incisional infection and no cases of early PJI. Seven cases of late PJI (0.41%) were diagnosed and underwent two-stage revision arthroplasties, among whom 2 patients had a history of being treated for suspected SII. Our rate of PJI is in concert with recent reported rates (22).
A discussion needs to be made on how to diagnose superficial incisional infections after TKA. To the best of our knowledge, there is no unified approach in the literature on this matter and CDC criteria are not designed, specifically for post-TKA infections. Our approach was to detect all cases suspected of having a superficial incisional infection and treating them with a short course of antibiotics. We can’t be sure if these 32 cases were in fact, infections, or solely inflammations or hypersensitivity reactions to Monocryl stitches. There was a 6-month period of time from April 2016 to September 2016, when an increase in these cases was observed (10 cases). After intense scrutiny, we found similar reports from other centers in Tehran using the same brand of Monocryl as ours. After switching to rapid Vicryl, the SII rate declined. The role of stitches in TKA wound complications has been reported before (34). We cannot still be sure how many suspected SIIs were actually stitch reactions. Howbeit, the fact that most cases happened close to one month after surgery (the time that Vicryl starts to resorb) makes this explanation more convincing. Indeed, it seems that even the quality of stitches we used has been seriously affected by tight economic sanctions. There were no records of SII over the last year of the study time.
There were some key routine practices that possibly prevented higher infection rates in our study.
First and foremost, it is the oriented and highly trained operating room (OR) personnel who understood the importance of infection control and strict infection prevention standards. Second is our approach to early wound infection. During postop follow-up examinations, if the surgical wound showed signs of erythema and/or warmth and/or itching and/or increased local pain at the surgical wound, superficial incisional infection was suspected and a one-week course of oral Levofloxacin 500mg twice daily was prescribed. This might have been a factor in the low rate of PJI among our recorded cases of SIIs. We do not use CDC criteria for surgical site infection, as it is not specifically designed for knee arthroplasty. Pain, tenderness and/or swelling which are mentioned in CDC criteria, occur in the early postoperative period of most TKAs and do not seem specific enough to diagnose a superficial infection. In fact, in knee arthroplasty, due to cumbersome management and poor outcomes of PJI, we need early diagnosis of any superficial infection and wound drainage or positive culture mentioned in the CDC criteria would procrastinate diagnosis and prevent early intervention. The third probable factor, could be the use of intrawound vancomycin powder before water-tight closure of the joint capsule. Since we started routine use of vancomycin powder in the wound at the end of TKA surgeries the infection rate decreased significantly (P=0.002). The effect of vancomycin powder on infection rate has not been proved in TKA (17-19), in contrast to spine surgery where it has been well established (14-16). Although we report promising results, its effectiveness cannot be proved based on the current study either.
The strengths of this study include a large sample size and enrolling consecutive patients to decrease selection bias. Also, all the arthroplasties were performed by a single surgeon with a unified surgical technique, which eliminates the confounding effect of different surgical techniques. Nevertheless, there is an inherent probability of selection bias due to implementing historical control subjects and lack of randomization (35). Despite our results, determining the exact effect of intrawound vancomycin on the rate of deep infection after TKA, needs prospective randomized controlled trials designed specific for its use in knee arthroplasty surgery (36, 37).