Preventive measures

The experimental evidence concerning the effect of foreign material on the pathogenesis of bacterial infection (see section 5.3.4, p. 26) and the dramatic consequences of infected joint replacement (see section 5.6, p. 53) give reason to emphasize the importance of asepsis for joint replacement surgery. The very early experiments with knee replacement surgery in the late 19th century failed due to sepsis shortly after operation (Eynon-Lewis et al. 1992). Later, the introduction of aseptic surgical techniques in the 1960s was crucial for the triumph of joint replacement surgery.

The routine preventive measures that are common for any types of surgery are thoroughly listed and described in the CDC 1999 Guideline for prevention of surgical site infection (Mangram et al. 1999). These measures include preoperative preparation of the skin in the operating room using antiseptic agents, preoperative wash and sterilization of surgical team members’ hands and forearms, use of surgical scrub suits, caps or hoods and masks, sterile gloves and gowns (all worn by the operating team members) and surgical drapes placed over the patient. Clothing and masks act as a measure against infection but also protect the staff from exposures to blood and other fluid or dust. Double gloving reduces the probability of direct contact between staff and patient tissue. The preventive measures listed above are also appropriate in joint replacement surgery, and for many these

practices represent a part of the daily routine praxis and form the basis for infection prevention.

5.5.4.1 Operating room ventilation

In addition to direct contact from the surgical staff or instrumentation, air in the operation room serves as a source of bacterial contamination. The bacteria may originate from the surfaces of the operating room equipment, from outside the operating room or may be shed by the staff.

According to the CDC guidelines, operating rooms should be at positive pressure compared to adjacent areas to minimize the probability of contamination from outside the surgical field. For the same reason, the number of personnel in the room and traffic should be minimized (Mangram et al. 1999). High efficiency particulate air filters dramatically reduce the numbers of potentially infectious particles in the air but have no effect on the probability of contamination originating in the operating room. Laminar airflow, instead, can be used to sweep potentially hazardous particles away from the operating field.

The effect of operating room ventilation on the postoperative infection rates was analyzed in a series of studies performed in the late 1970s. In a frequently cited multicenter study of 8,052 hip and knee replacements (summarized in Lidwell et al.

1987) the rate of PJI was 2.6 times less with a laminar airflow of ultra-clean air over the operating field than in conventionally ventilated operating rooms. In another study, horizontal airflow, however, was associated with increased probability of infected TKR (Salvati et al. 1982). Currently, vertical laminar flow is a standard in modern orthopedic operating rooms.

Now that systemic antibiotic prophylaxis (see section 5.5.4.2 below) is being used routinely in elective TKR the rationale for laminar airflow systems and body exhaust suits has been questioned (Miner et al. 2007). In the early study by Lidwell and co-workers (1987) the lowest rate of infections (0.2%) was seen in when the three techniques were combined. This result has, however, been criticized as the use of antibiotic prophylaxis was not allocated randomly in the different groups under comparison. Moreover, the indications and patient materials were different from those in current practice. In a recent survey of 8,288 knee replacements performed

in 295 US hospitals neither laminar airflow nor body exhaust suits had any effect on the early infection rate (Miner et al. 2007). Unfortunately, methodological limitations precluded the analysis of possible confounding variables, and the relative importance of different prophylactic measures in modern surgical practice remains unknown.

5.5.4.2 Systemic antibiotic prophylaxis

The purpose of antibiotic prophylaxis is to help host defense mechanisms to control the burden of perioperative contamination of the surgical wound (Mangram et al.

1999). As it is targeted both against airborne contamination and contamination by direct contact, antibiotic prophylaxis supplements other preventive measures.

Following the clinical experience in hip replacement surgery the practice of using systemic antibiotic prophylaxis has been adopted in knee surgery although its effectiveness has not been established in this field of surgery.

Cephalosporins are currently the most commonly used prophylactic agents in orthopedic surgery (Mangram et al. 1999, National Agency for Medicines 2008).

Their advantages are good efficacy against staphylococcal species and uropathogens, low cost and modest allergenicity. One preoperative dose (1,500 mg) of cefuroxime seems sufficient (Wymenga et al. 1992) unless there are special reasons, such as breakage of sterility or excess bleeding, to continue antibiotic prophylaxis longer.

The ideal timeframe for administering prophylactic antibiotic is within 60 minutes prior to incision (Mangram et al. 1999) – or at the latest before applying the tourniquet. In prolonged surgeries, such as bilateral knee replacements (Huotari et al. 2007c), additional doses may be required to maintain sufficient antimicrobial concentrations in the operation field (Mangram et al. 1999).

5.5.4.3 Antibiotic-impregnated cement

Bone cement used for prosthesis fixation provides an alternative or additional way to administer prophylactic antibiotics. While some authors question the rationale behind routine use of antibiotic-impregnated cement (van de Belt et al. 2001,

Hanssen 2004), others think that antibiotic-impregnated cement has been one of the main contributors for the decline in the PJI rates (Bourne 2004). Currently, antibiotic-impregnated cement is used commonly even in non-complicated primary cases especially in the Nordic countries (Engesæter et al. 2006, National Agency for Medicines 2008).

The evidence to support the use of antibiotic-impregnated cement as a measure against PJI comes largely from hip replacement surgery (Josefsson and Kolmert 1993, Espehaug et al. 1997, Engesæter et al. 2003). In knee arthroplasty, Chiu and associates (2001, 2002) demonstrated the efficacy of cefuroxime-impregnated cement in patients with diabetes and in general population undergoing TKR. No infected knee replacement occurred in the group receiving antibiotic-impregnated cement group whereas in the comparison groups receiving systemic antibiotic prophylaxis only the PJI rates were 13.5% (diabetic patients) and 3.1% (general population). A similar result was achieved in a French cohort study based on infection surveillance data (deep wound infection rates 1.52% and 9.52% in cases with and without gentamycin-impregnated cement) (Eveillard et al. 2003).

It is of note that the studies by Chiu and co-workers (2001, 2002) were performed in the absence of laminar airflow and ultra-clean air measures. Nevertheless, antibiotic-impregnated cement appears effective in the prevention of infected TKR.

At present, there is, however, insufficient data to compare different ways of antibiotic administration with other preventive measures – or with combinations of several techniques – and to define specific indications for different prophylactic measures.