Optimizing the Patient

Assessment of the general medical health of each patient with a thorough history and physical examination is an important precursor for infection prevention. Several medical comorbidities have been shown to generate a significant propensity for infection, most notably diabetes, rheumatoid arthritis, obesity, and immunosuppression (including chronic steroid use). The combination of these comorbidities is demonstrated to significantly increase the overall risk for infection. Special care should be taken in selecting patients with manageable medical comorbidities and optimizing all current medical issues before proceeding with TJA.

Infection Starts with the Host

Surgical site infection (SSI) and wound drainage greater than 48 hours has been correlated to the development of PJI. In addition to optimizing the patient’s ability to heal postoperatively, prevention of SSI involves minimizing risk from superficial bacterial sources. A study by von Eiff and colleagues used the bacterial genotype to demonstrate that 80% of nosocomial SSIs originated from native endogenous Staphylococcus aureus . The prevalence of colonization with S aureus has been dropped from 32.4% to 28.6% of infections, whereas the prevalence of methicillin-resistance S aureus (MRSA) has increased from 0.8% to 1.5%. Both S aureus and MRSA colonization have been associated with a significant increase in risk for SSI. In a study by Yano and colleagues preoperative screening for nasal colonization of MRSA in orthopedic patients revealed that 4% of patients had MRSA-positive nasal cultures of which 26% developed MRSA wound infections. Conversely, of the patients with negative nasal colonization, only 1.3% developed SSI.

However, whether SSIs result from exogenous bacterial contamination or endogenous self-inoculation and colonization is still controversial. Although intranasal S aureus colonization is a risk factor for orthopedic SSI, most postoperative bacterial strains recovered from the surgical suites were different strains than those identified in preoperative nasal samples. Despite the uncertainty of the origin, several studies have shown the effectiveness of implementation of prehospital screening and decolonization protocols in decreasing SSI. Decolonization protocols started 5 days before surgery include combination of nasal mupirocin ointment, chlorhexidine total body wash, and chlorhexidine mouth rinse and have been demonstrated to reduce postoperative infections. Buehlmann and colleagues revealed that such preadmission protocols were 98% effective in preventing PJI and decolonizing the nares and groin. In contrast, Wendt and colleagues compared decolonization protocols with a placebo group in various regions of the body and reported that preadmission decolonization protocols were only successful in eradicating MRSA from the groin, but not the nares, throat, or perineum.

Skin Preparation

It is beneficial to thoroughly examine the patient’s skin in the office and in the preoperative area. Detection of abrasions, bruising, ulcers, pet scratches, psoriatic patches, or cellulitis should be routine practice and may reduce the risk for wound infections. It is important to appreciate existing incisional scars. Incorporating previous incisions into the new incision decreases the risk for devascularized skin bridges, postoperative skin necrosis, and subsequent wound infection. Removal of hair around the incision site has become a routine part of the preoperative preparation. There are limited data to support hair removal in prevention of SSI. A Cochrane review article showed no statistical difference between hair removal and decrease in SSI. In fact, SSI statistically increased when hair was removed with a razor as compared with clippers. Alcohol or aqueous skin preparations have been shown to have a skin penetration of only 300 μm. This leaves viable bacteria deep inside hair follicles and skin recolonization may occur in 30 minutes. Although, hair removal does not reduce the risk for SSI, it does improve surgical site visibility. When implemented, it is recommended that hair be removed immediately before surgery with an electric clipper, minimizing bacterial recolonization and epidermal abrasions.

Several preoperative skin preparations are currently available; however, no one agent has superiority over the other. Investigators have compared the use of preparation regimens containing DuraPrep (3M Company, St. Paul MN) solution and a povidone-iodine scrub before TJA. Both methods were found to be equivalent in reducing the frequency of SSIs and PJIs. The addition of alcohol to aqueous skin preparations, such as chlorhexidine, has been shown to be beneficial, but has the disadvantage of drying out the skin’s top layer. Disruption of the most superficial skin layers aids bacterial proliferation. The use of skin preparation agents, such as Avagard (3M Company), moisturizes the skin preventing its drying.

Draping out the prepared surgical area is an important step in conserving sterility and decreasing the risk for infection. Care must be taken to only isolate skin that has been adequately sterilized. Plastic adhesive drapes have shown decreased rates of contamination when compared with traditional cloth drapes. Use of an iodine-impregnated drape, such as Ioban (3M Company), may theoretically decrease PJI. A Cochrane article reviewed more than 3000 patients in five different studies and found no significant decrease in PJI with antimicrobial-incorporated adhesive drapes. Appropriate draping including a water-tight seal around nonsterilized skin and use of adhesive drapes over the incision site is imperative to maintain sterility and decrease infection rates.

Prophylactic Antibiotics

Systemic prophylactic antibiotic use before TJA has been shown in several studies to reduce the rate of infection. In a recent meta-analysis of seven studies, antibiotic prophylaxis reduced the absolute risk of SSI in TJA by 8% and the relative risk by 81% compared with no antibiotic prophylaxis. Antibiotics need to be effective against organisms responsible for postoperative infections, such as S aureus , Staphylococcus epidermidis , Escherichia coli , and Proteus . Currently, the American Academy of Orthopedic Surgeons recommends antibiotics for prophylaxis with a first- or second-line cephalosporin, most commonly cefazolin and cefuroxime, in the absence of a β-lactam allergy. Clindamycin, vancomycin, or teicoplanin can be used in the presence of a documented cephalosporin allergy or known antibiotic-resistant organism, such as MRSA. Given the increasing prevalence of MRSA, it is important to recognize patients who are at higher risk of being colonized. Risk factors for MRSA include recent antibiotic use, hospitalization, female sex, diabetes, age greater than 65 years, human immunodeficiency virus, or health care workers. Those patients should have their prophylactic antibiotics adjusted accordingly.

Fulkerson and colleagues examined bacterial cultures from infected TJA and susceptibilities to prophylactic antibiotics. They found that only 61% of bacterial isolates were sensitive to cefazolin. In patients previously treated with antibiotics, the vancomycin sensitivity was only 78%, and cefazolin sensitivity was 0%. Sewick and colleagues examined the use of a dual antibiotic prophylaxis with preoperative cefazolin and vancomycin on 1828 TJAs. They found no statistical difference in SSI when compared with cefazolin alone. The use of vancomycin as a primary prophylactic antibiotic is controversial and current literature supports primary prophylaxis with a first- or second-line cephalosporin when applicable.

To reach minimal inhibitory concentration, prophylactic antibiotics should be initiated within 1 hour of start of the procedure. Several studies confirm that 24 hours of antibiotics is as effective as 48 or 72 hours. Current recommendations include one intraoperative dose of antibiotics followed by one or two additional perioperative doses. A second additional dose of antibiotics may be administered during prolonged surgical duration beyond the half-life of the antibiotic (typically 4 hours) or when blood loss exceeds 1000 mL.

Our Own Worst Enemy

A potential source for intraoperative wound contamination includes airborne bacteria. These bacteria almost commonly originate from operating room staff. Bacterial shedding from one operating room staff member can be 10,000 bacteria per minute. When compared with a completely empty operating room, the addition of five personnel increases the airborne microbial count 15-fold. This source of contamination has been well documented over the years. In fact, Charnley is credited with saying, “The living body of personnel in an operating room is by far the most important source of pathogenic organisms.” Several techniques have been implemented to minimize the circulating airborne bacterial load and promote a “clean air” environment.

Traffic Control

Ambient airborne particulate and bacteria counts increase because of bacterial shedding from operating room personnel and air exchange between the sterile operating room and nonsterile hallways. The repeated opening and closing of operating room doors has been shown to be a predictor of the number of airborne particulates in an operating room. In the modern operating room, restricting presence to only scrubbed sterile personnel is not practical because most operating room staff must regularly travel between operating rooms. To combat airborne contamination, clean air enclosures have been established within the operating room. This allows anesthesia and other unscrubbed personnel to remain physically separate from the sterile surgical field. Currently, there are little data to support the use of clean air enclosures within the operating room. Although some amount of foot traffic within the operating room is to be expected, excessive use of the operating room doors and increased number of personnel should be discouraged.

Space Suits and Laminar Flow Systems

Lidwell and colleagues first examined the use of ultraclean laminar air flow (LAF) systems in the operating room for control of airborne contamination compared with typical turbulent flow rooms. They examined greater than 8000 operating rooms and found a 75% decrease in SSI with LAF compared with a control room. Historically, use of LAF without the use of preoperative antibiotics was shown to decrease the prevalence of SSI from 3.4% to 1.2%. Vertical LAF units have demonstrated 80% to 93% reduction in environmental and surface contamination. The accepted airborne bacterial counts for ultraclean LAF is less than or equal to 10 cfu/m ³ . When combined with the use of body exhaust systems (BES), operating room bacterial counts decrease to 1 cfu/m ³ . Ritter and colleagues showed that BESs reduce airborne contamination by 38% when compared with sterile gowns and up to 69% when compared with plain surgical scrubs. Despite several studies showing the significant decrease in airborne contamination with the combination of LAF and BES, the efficacy of these methods at decreasing infection rates is still controversial. Hooper and colleagues analyzed greater than 51,000 primary THAs and greater than 36,000 TKAs assessing LAF and BES use and the rate of revision for early deep infection. Their data failed to demonstrate any decrease in the rate of infection in either modality. Similarly, Ahl and colleagues showed no statistical difference in deep infection rate when examining greater than 8000 TKAs with laminar flow rooms and body suits. Whyte and colleagues revealed that air contamination does not significantly reflect surface contamination, and proposed surface bacteria as a more substantial risk factor for SSI. Ultraclean laminar flow systems and BES remain extremely popular in TJA despite debate over their efficacy.

An alternative to using LAF systems to reduce the number of airborne bacterial and particulate load in addition to decreasing surface contaminates involves directly killing bacteria using ultraviolet lighting (UVL). UVL at 290 μW/cm ² has been shown to decrease surface bacterial counts more than with LAF alone. Ritter and colleagues prospectively examined 5890 TJA with and without UVL and revealed a 3.1 times decrease in SSI, solely by using UVL. Although effective in preventing SSI, there exist safety concerns for patient and personnel because of the carcinogenic properties of UVL. Currently, the Centers for Disease Control and Prevention and National Institutes of Health recommend against the use of UVL, citing significant safety hazards. The use of UVL seems to be an effective adjunct to ultraclean air operating room environment and with proper operating room staff and patient protective equipment, could be a cost-effective addition or alternative to LAF.

Intraoperative Anesthesia Measures

The anesthesia team plays an important intraoperative role in the prevention of postoperative wound complications and deep infections. During the procedure, the anesthesia team is responsible for implementing protocols to optimize postoperative healing. This includes an appropriate timing of perioperative antibiotics, intraoperative monitoring of blood glucose, and temperature controls.

Because of the increase in physiologic stress during the operation, insulin requirements are typically elevated. This is especially important with patients with decreased insulin response, such as type 1 and 2 diabetes. An estimated 8% of all TJAs are performed on patients with diabetes. Frequent intraoperative blood glucose monitoring is also encouraged and is of particular importance in patients with type 1 diabetes. Continual postoperative glycemic checks are required because insulin requirements may fluctuate as the patients metabolic needs readjust.

Mild hypothermia during a major operation is a common event. This has been shown to trigger thermoregulatory vasoconstriction and decrease subcutaneous perfusion and oxygen tension and promote postoperative wound infection. Reduction of oxygen tension may also impair the oxidative mechanism of neutrophils, decreasing the tissues ability to immunogenic and anabolic activity. Hypothermia also directly impairs function of the patient’s natural overall immune function. A multicenter, randomized controlled trial assessing intraoperative warming in colorectal patients demonstrated that patients with normothermia had a significantly lower risk of developing postoperative infections than their hypothermic counterparts (6% vs 19%, respectively). Hence, intraoperative normothermia is likely to decrease SSI in patients undergoing major TJA and should be implemented by the anesthesia team.

Antibiotic Bone Cement

Prevention of infection in TJA may be augmented with the use of antibiotic-impregnated cement. The addition of heat-resistant antibiotics to bone cement allows for the direct delivery of antimicrobials to the area with the greatest concern. Antibiotic-impregnated cement has been demonstrated to have bactericidal activity for at least 7 to 10 days following implantation and up to 10 years in some studies. Antibiotic-loaded bone cement (ALBC) allows for the delivery of high antibiotic concentrations at the operative site, reducing the adverse systemic effects while increasing antibiotic concentration at the surgical site. The use of ALBC in conjunction with systemic antibiotics has been shown to decrease wound infection and PJI revision rates. A randomized prospective study by Chiang and Chiu examined the prophylactic use of ALBC in primary TKAs and compared their outcomes with standard polymethyl methacrylate bone cement. In the cohort receiving ALBC, no infections were reported, whereas the standard polymethyl methacrylate cohort had a 3.1% infection rate.

Despite the promising data, the use of ALBC continues to be controversial. Concerns regarding routine use of ALBC in primary TJA include decreasing bone cement strength, development of antibiotic resistance, hypersensitivity reactions, and increased cost. Although the addition of large amounts of antibiotics to bone cement can alter cement properties, the use of lower doses has been shown to have negligible mechanical effects. The increased cost associated with the use of ALBC can adversely affect the use of TJA. To offset increased cost of approximately $60,000 per 100 patients undergoing TJA, the decrease in infection incidence needs to be greater than 1.2%. However, the use of prophylactic ALBC in high-risk patients with a history of bacterial infections or immunocompromised status is generally well accepted. Although still controversial, the use of prophylactic ALBC has been demonstrated to be effective and beneficial in properly selected patients with TJA.