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General Principles of Infection
Etiology
Bone and joint infections pose a formidable challenge to the orthopaedic surgeon. The high success rate obtained with antibiotic therapy in most bacterial diseases has not been obtained in bone and joint infections because of the physiologic and anatomic characteristics of bone. Approximately 80 million surgical cases are performed in the United States yearly, and with the rise in aging population, this will most likely increase. The overall surgical site infection (SSI) rate has been estimated by the U.S. Centers for Disease Control and Prevention (CDC) to be 2.8% in the United States. Approximately 300,000 SSIs occur each year in the United States, with affected patients requiring 6.5 more hospital days on average, which increases the cost of surgery two to five times. Although bacteremia is common (estimated to occur 25% of the time after simple tooth brushings), other etiologic factors must be present for an infection to occur. The mere presence of bacteria in bone, whether from bacteremia or from direct inoculation is insufficient to produce osteomyelitis. Illness, malnutrition, and inadequacy of the immune system can contribute to bone and joint infections. As in other parts of the body, bones and joints produce inflammatory and immune responses to infection. Osteomyelitis occurs when an adequate number of a sufficiently virulent organism overcomes the host’s natural defenses (inflammatory and immune responses) and establishes a focus of infection. Local skeletal factors also play a role in the development of infection. For example, the relative absence of phagocytic cells in the metaphysis of bones in children may explain why acute hematogenous osteomyelitis is more common in this location.
The peculiarity of an abscess in bone is that it is contained within a firm structure with little chance of tissue expansion. As infection progresses, purulent material works its way through the Haversian system and Volkmann canals and lifts the periosteum off the surface of bone. The combination of pus in the medullary cavity and in the subperiosteal space causes necrosis of cortical bone. This necrotic cortical bone, known as a sequestrum, can continue to harbor bacteria despite antibiotic treatment. Antibiotics and inflammatory cells cannot adequately access this avascular area, resulting in failure of medical treatment of osteomyelitis.
Recognizing these unique characteristics of bone infections, the best course of action is prevention. The orthopaedic surgeon should evaluate the risk of infection in each patient by considering patient-dependent and surgeon-dependent factors. Patient-dependent factors include nutrition, immunologic status, alcohol abuse, smoking, infection at a remote site, congestive heart failure, depression, and other comorbidities ( Table 20.1 ). Surgeon-dependent factors include prophylactic antibiotics, skin and wound care, operating environment, surgical technique, and treatment of impending infections, such as in open fractures. Duration of hospital stay also has been directly correlated with an increased risk of SSI. Simply stated, it is much easier to prevent an infection than it is to treat it.
Table. 20.1
Summary of Risk Factors Associated With Development of Surgical Joint Infection/Prosthetic Joint Infection
From Zainul-Abidin S, Amanatullah DF, Anderson MB, et al: General assembly, prevention, host related general: proceedings of international consensus on orthopedic infections, J Arthroplasty 34(2S):S13–S35, 2019.
| Nonmodifiable Host Factors | Modifiable Host Factors | Factors With Limited Evidence of Associations With Ssi/Pji |
|---|---|---|
| Age (≥75 years)—moderate | BMI—strong | Age—(as a continuous exposure)—limited |
| Male sex—strong | Smoking—strong | Hispanic ethnicity—limited |
| Black race—strong | High alcohol intake (alcohol abuse)—strong | Native American and Eskimo ethnicity—limited |
| TKA vs. THA—strong | Low income—strong | Asian race—limited |
| Malnutrition (low serum albumin)—strong | History of drug abuse—limited | |
| History of DM—strong | Rural location vs. nonrural location—limited | |
| History of CVD—moderate | Underweight—limited | |
| History of CHF—strong | History of hypertension—limited | |
| History of cardiac arrhythmia—strong | History of osteoarthritis—limited | |
| History of peripheral vascular disease—strong | History of posttraumatic arthritis—limited | |
| Chronic pulmonary disease—strong | Low- or high-risk dental procedures—limited | |
| Chronic obstructive pulmonary disease | History of urinary tract infection—limited | |
| History of renal disease—strong | History of dementia—limited | |
| History of liver disease/cirrhosis—strong | Hypercholesterolemia—limited | |
| History of RA—strong | Peptic ulcer disease—limited | |
| History of cancer/malignancy—strong | Valvular disease—limited | |
| History of osteonecrosis—strong | Metastatic tumor—limited | |
| History of depression—strong | History of coagulopathy—limited | |
| History of psychosis—strong | History of venous thromboembolism—limited | |
| History of HIV/AIDS—strong | Pulmonary circulatory disorders—limited | |
| Neurologic disease (hemiplegia, paraplegia)—moderate | Hypothyroidism—limited | |
| History of corticosteroid administration—strong | Hepatitis (B or C)—limited | |
| History of intra-articular corticosteroid injection—moderate | Electrolyte imbalance—limited | |
| Previous joint surgery—strong | Autogenous blood transfusion—limited | |
| Revision arthroplasty—strong | ||
| Previous joint infection—moderate | ||
| Frailty—moderate | ||
| Preoperative anemia—strong | ||
| American Society of Anesthesiologists grade >2—strong | ||
| Charlson comorbidity index (high)—strong | ||
| Preoperative hyperglycemia and high HbA1c—moderate | ||
| Allogenic blood transfusion—strong | ||
| Prophylaxis with warfarin or low-molecular weight heparin—moderate |
BMI , Body mass index; CHF , congestive heart failure; CVD , cardiovascular disease; DM , diabetes mellitus; PJI , periprosthetic joint infection; RA , rheumatoid arthritis; SSI , surgical site infection; THA , total hip arthroplasty; TKA , total knee arthroplasty.
Patient-dependent factors
It has been discovered that up to 80% of patients have at least one modifiable risk factor that, if corrected, could decrease the risk of SSI. Alcohol abuse, for instance, doubles the risk, and tobacco use more than triples the risk for infection. These substances should be discontinued 1 month before surgery is recommended. Intra-articular injections also should be discontinued 3 to 6 months before elective surgery, and any poor dentition issues should be treated.
Nutritional status
A patient’s nutritional status and immunologic response are important. A body mass index greater than 40 is associated with an eight times greater risk for SSI. Despite their appearance, obese patients are frequently malnourished. In fact, over half of patients are noted to be malnourished. If a patient is malnourished or immunocompromised and cannot mount a response to an infection, the effects of any treatment are diminished. Malnutrition adversely affects humoral and cell-mediated immunity, impairs neutrophil chemotaxis, diminishes bacterial clearance, and depresses neutrophil bactericidal function, the delivery of inflammatory cells to infectious foci, and serum complement components. Basal energy requirements of a traumatized or infected patient increase from 30% to 55% of normal. Fever of just 1°F above normal increases the body’s metabolic rate by 13%.
Nutritional status can be determined preoperatively by (1) anthropometric measurements (height, weight, triceps skinfold thickness, and arm muscle circumference), (2) measurement of serum proteins or cell types (lymphocytes), and (3) antibody reaction to certain antigens in skin testing.
Nutritional support is recommended before elective surgery for patients with recent weight losses of more than 10 lb, serum albumin levels less than 3.5 g/dL, or lymphocyte counts of less than 1500 cells/mm 3 , which can be obtained from a routine complete blood cell count and BMP-24. With the use of serum albumin and transferrin levels, the formula that follows can be used to screen for patients who may need nutritional support: [(1.2 × serum albumin) + (0.013 × serum transferrin)] − 6.43. If the sum is 0 or a negative number, the patient is nutritionally depleted and is at high risk for sepsis. If nutritional support is needed, enteral therapy should always be used when the gastrointestinal tract is functional; if not, hyperalimentation must be employed. Vitamin D deficiency also has been linked to an increase in SSIs. Vitamin D levels should be obtained preoperatively, and any deficiencies corrected at that time.
Glucose
Glycemic control is a patient modifiable risk factor that can lead to a decrease in SSI. The optimal hemoglobin A1c (HbA1c) has yet to be determined. Some advocate 7%, whereas others believe 8% is the correct value for risk stratification. Fructosamine levels have been utilized to detect hyperglycemia especially in the 2 to 3 week period before surgery. A level greater than 292 mmol/L has been shown to be a better indicator of deep infection than HbA1c (>7%). Most agree that hyperglycemia, even in nondiabetic patients, is a risk factor for developing SSI. A glucose level greater than 200 mg/dL requires treatment before elective surgery.
Rheumatoid Arthritis
The incidence of periprosthetic joint infection (PJI) is 1.6 times higher in patients with rheumatoid arthritis than with osteoarthritis. Most believe that this is associated with their use of disease-modifying antirheumatic drugs. To decrease the incidence of SSI in this population, it is recommended that these medications be discontinued according to their half-life and resumed 2 weeks postoperatively.
Immunologic status
To fight infection, the patient must mount inflammatory (white blood cell [WBC] count) and immune (antibody) responses that initially stop the spread of infection and then, ideally, destroy the infecting organisms. The body’s main cellular defense mechanisms are (1) neutrophil response, (2) humoral immunity, (3) cell-mediated immunity, and (4) reticuloendothelial cells. A deficiency in production or function of any of these predisposes the host to infection by specific groups of opportunistic pathogens. Deficiencies in the immune system may be acquired or may result from congenital abnormalities. Immunocompromised hosts are not susceptible to all opportunistic pathogens. The susceptibility to a microorganism depends on the specific defect in immunity. Abnormal neutrophils or humoral and cell-mediated immunities have been implicated in infections caused by encapsulated bacteria in infants and elderly patients, in the increased incidence of Pseudomonas infections in heroin addicts, and in Salmonella and Pneumococcus infections in patients with sickle cell anemia.
Diabetes, alcoholism, hematologic malignancy, and cytotoxic therapy are common causes of neutrophil abnormalities. If the neutrophil count decreases to less than 55/mm 3 , infections caused by Staphylococcus aureus, gram-negative bacilli, Aspergillus organisms, and Candida organisms become a major threat.
Immunoglobulins and complement factors are two plasma proteins that play crucial roles in humoral immunity. Patients with hypogammaglobulinemia or who have had a splenectomy are at increased risk of infection caused by encapsulated bacteria, such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria organisms. When a defect in a component of the complement cascade is present, S. aureus and gram-negative bacillus infections are common. Septic arthritis caused by unusual organisms such as Mycoplasma pneumoniae and Ureaplasma urealyticum has been reported and should be suspected in patients with hypogammaglobulinemia and culture-negative septic arthritis.
Cell-mediated immunity depends on an interaction between T lymphocytes and macrophages. Primary cell-mediated deficiencies are rare, but secondary cell-mediated deficiencies are common. Corticosteroid therapy, malnutrition, lymphoma, systemic lupus erythematosus, immunodeficiency in elderly patients, and autoimmune deficiency syndrome all can cause a secondary cell-mediated deficiency, which predisposes the host to fungal and mycobacterial infections as well as infection with herpes virus and Pneumocystis jiroveci .
Vaccinations also play a role in host response. The hepatitis B vaccine has dramatically reduced the incidence of hepatitis B virus (HBV), and the H. influenzae type B vaccine, that is given to children, has all but eliminated musculoskeletal infections caused by H. influenzae.
Surgeon-dependent factors
Skin preparation
Wound contamination exists whenever the skin barrier is broken, but proper skin preparation decreases the contamination caused by bacteria present on the skin. Skin barriers also may decrease skin contamination during surgery. Although the skin can never be disinfected completely, the number of bacteria present can be reduced markedly before surgery. The skin and hair can be sterilized with alcohol, iodine, hexachlorophene, or chlorhexidine, but it is almost impossible to sterilize the hair follicles and sebaceous glands where bacteria normally reside and reproduce. Skin preparations have a limited effect on sebaceous glands and hair follicles because they do not penetrate an oily environment. Disinfectants that penetrate the oily environment are absorbed by the body and have potentially toxic side effects. Hexachlorophene has better penetration but also has neurotoxic side effects. Very few level I evidence-based studies discuss if preoperative skin antiseptics actually decrease SSI and, if so, the correct method of cleansing. Most agree that the patient should bathe the night before surgery with soap and water. Some advocate adding chlorhexidine wipes. A Cochrane Library systematic review concluded that 4% chlorhexidine in 70% alcohol had the most favorable results in reducing SSI. Most agree that some form of alcohol needs to be employed with whatever skin preparation is used, whether it be chlorhexidine or iodophor. We agree with the CDC guidelines for skin preparation with slight modifications:
- 1.
The size of the area being prepared should be enough to include any additional exposure that may be required.
- 2.
The solution should be applied in concentric circles from the incision site peripherally.
- 3.
A dedicated instrument may be utilized that is removed from the operative field after preparation and before draping (i.e., sponge clamp).
- 4.
Time should be allowed for the alcohol to dry because a fire risk exists .
Hand washing is the single-most important procedure for prevention of nosocomial infections and should be performed before and after each patient encounter. Studies suggest that hand scrubbing for 2 minutes is as effective as traditional hand scrubbing for 5 minutes. The optimal duration of hand scrubbing has yet to be determined. Hand rubbing with an aqueous alcohol solution that is preceded by a 1-minute nonantiseptic hand washing for the first case of the day was found by Parienti et al. to be just as effective in prevention of SSI as traditional hand scrubbing with antiseptic soap. The effectiveness of common antiseptics is summarized in Table 20.2 .
Table. 20.2
Antimicrobial Activity ∗ and Summary of Properties of Antiseptics Used in Hand Hygiene
From Pittet D, Allegranzi B, Boyce J, et al: The World Health Organization guidelines on hand hygiene in health care and their consensus recommendations. Infec Control Hosp Epidemiol 30:611–622, 2009.
| Antiseptics | Gram-positive bacteria | Gram-negative bacteria | Viruses enveloped | Viruses nonenveloped | Mycobacteria | Fungi | Spores |
|---|---|---|---|---|---|---|---|
| Alcohols | +++ | +++ | +++ | ++ | +++ | +++ | − |
| Chloroxylenol | +++ | + | + | ± | + | + | − |
| Chlorhexidine | +++ | ++ | ++ | + | + | + | − |
| Hexachlorophene † | +++ | + | ? | ? | + | + | − |
| Iodophors | +++ | +++ | ++ | ++ | ++ | ++ | ± ‡ |
| Triclosan ¶ | +++ | ++ | ? | ? | ± | ± ¶ | − |
| Quaternary ammonium compounds § | ++ | + | + | ? | ± | ± | − |
| Antiseptics | Typical Conc. In% | Speed of Action | Residual Activity | Use |
|---|---|---|---|---|
| Alcohols | 60%–70% | Fast | No | HR |
| Chloroxylenol | 0.5%–4% | Slow | Contradictory | HW |
| Chlorhexidine | 0.5%–4% | Intermediate | Yes | HR/HW |
| Hexachlorophene † | 3% | Slow | Yes | HW, but not recommended |
| Iodophors | 0.5%–10% | Intermediate | Contradictory | HW |
| Triclosan || | 0.1%–2% | Intermediate | Yes | HW; seldom |
| Quaternary ammonium compounds § | Slow | No | HR, HW; Seldom; +alcohols |
Good = +++, moderate = ++, poor = +, variable = ±, none = −
HR, Hand rubbing; HW , hand washing.
∗ Activity varies with concentration.
‡ In concentrations used in antiseptics, iodophors are not sporicidal.
¶ Activity against Candida spp ., but little activity against filamentous fungi.
§ Bacteriostatic, fungistatic, microbicidal at high concentrations.
Hair removal at the operative site is not recommended unless done in the operating room with clippers. Shaving the operative site the night before surgery can cause local trauma that produces a favorable environment for bacterial reproduction.
Prevention of infection transmission between the patient and the surgeon also includes proper surgical attire. Edlich et al. showed that a narrow glove gauntlet (cuff) significantly increased the security of the gown-glove interface. The U.S. Food and Drug Administration accepts there is a 2.5% failure rate of new unused sterile gloves. Glove perforation has been reported to occur in up to 48% of operations. Perforations usually occur approximately 40 minutes into the procedure, and as much as 83% of the time the surgeon is unaware of the perforation. Most frequently, the perforation occurs on the index finger of the nondominant hand. Double gloving reduces the exposure rate by as much as 87%. In addition, double gloving decreases the volume of blood on a solid needle (through a wipe-clean pass mechanism from the outer glove) as much as 95%. A meta-analysis by Tanner and Parkinson found that double gloving decreased skin contamination, and the use of Biogel indicator gloves (Regent Medical, Norcross, GA) increased the awareness of glove perforation. A darker glove should be worn as the indicator glove. When both gloves were compromised, however, the indicator gloves did not increase the awareness of a perforation. As long as the indicator glove was intact, perforation of the outer glove was promptly detected in 90% of cases. Wearing an outer cloth glove over a latex glove significantly reduced the number of perforations to the innermost latex glove. When a liner glove was used between two latex gloves, the perforation rate of the innermost glove decreased. No reduction in perforations was seen when using an outer steel–weave glove. Double gloving does not provide reduction in perforations when tears occur as a result of geometry configurations such as bone or hollow-core needles. At a minimum, surgical gloves should be changed after draping, before handling implants, and then every 2 hours. No level I evidence exists currently that conclusively proves reduction of SSI with the use of surgical mask, caps, shoe covers, cloth versus disposable gowns, or operating room attire worn outside the hospital; however, experience dictates their usefulness. A very large number of patients will be required to sufficiently power future level I studies.
Operating room environment
Airborne bacteria are another source of wound contamination in the operating room. These bacteria usually are gram positive and originate almost exclusively from humans in the operating room; 5000 to 55,000 particles are shed per minute by each individual in the operating room. Conventional operating room air may contain 10 to 15 bacteria per cubic foot and 250,000 particles per cubic foot. The number of door openings and surgical personnel has been shown to increase the number of airborne particles and, therefore, should be kept to a minimum. Bouffant style hats allow significantly greater microbial shedding than disposable skull caps and perhaps should be avoided. In past research, airborne bacterial concentrations in the operating room were thought to be reduced by at least 80% with laminar-airflow systems and even more with personnel-isolator systems. Wound contamination rates have been reported to be reduced by 80% with the use of these systems, although an increased infection rate has been reported with the use of horizontal laminar flow after total knee arthroplasty, possibly from deposition of bacteria shed by scrubbed personnel who were not wearing personnel-isolator systems. However, most recent studies have shown that the use of laminar flow does not decrease SSI. At this time, laminar flow is no longer required. Ultraviolet light also has been noted to decrease the incidence of wound infection by reducing the number of airborne bacteria; however, the use of ultraviolet light rooms is not recommended by the Hospital Infection Control Practice Advisory Committee or the CDC because of the increased risk to surgical personnel of exposure to ultraviolet light. It can be employed as a method for terminal cleaning of the unoccupied operating room.
No level I evidence exists that forced air warming increases SSI; however, a multicentered pooled data study by Augustine showed a 78% reduction in SSI after discontinuing forced air warming. Normothermia has shown to decrease SSI.
Additional evidence exists for changing the scalpel after the first incision, changing the suction tip every hour, avoiding a back-table splash basin (the dirty pond), keeping operative time to less than 2.5 hours to decrease the occurrence of infection. Of note, low-pressure (bulb) lavage has been demonstrated to be equal to high-pressure (pulse) lavage. The addition of antibiotics to the irrigation fluid had no additional benefit and, therefore, is not recommended. Although little has changed in over 50 years in our use of surgical attire and little clinically based evidence exists for scrub masks, head coverings, iodine-impregnated plastic drapes, and many of our “standard sterile techniques,” we believe that the practices listed in Table 20.3 should be adhered to in an effort to minimize the risk of SSI.
Table. 20.3
Methods for Reducing Surgical Site Infection
Modified from Johnson R, Jameson SS, Sanders RD, et al: Reducing surgical site infection in arthroplasty of the lower limb. A multi-disciplinary approach, Bone Joint Res 2(3):58–65, 2013.
| PATIENT FACTORS | |
| Diabetes mellitus | Aggressive glucose control; if HgbA1c >7%, recommend delaying elective surgery DMARDs and methotrexate should NOT be stopped |
| Rheumatoid arthritis | Perioperative steroids are generally not required (stress dose steroids) Balance the risks and benefits of stopping anti-TNF at 3–5 half-lives preoperatively, restarting after wound healing and no evidence of infection |
| Obesity (BMI ≥30 kg/m 2 ) | Dietician input to encourage weight loss over long period before surgery without rapid weight loss preoperatively Adjust perioperative antibiotic doses appropriately In extremely obese, consider bariatric surgery before surgery |
| Smoking | Consider a smoking cessation program 4–6 weeks preoperatively |
| Carrier screening | MRSA and MSSA screening based on local guidelines, and decolonize before admission which may include mupirocin ointment to the area for 5 days and chlorhexidine betadine for 5 days |
| Oral hygiene | Complete any dental treatment before elective surgery |
| PREOPERATIVE FACTORS | |
| Patient preparation | Shower on day of surgery If shaving required, use electric clippers on day of surgery Avoid oil-based skin moisturizers |
| Antibiotics | Prophylactic antibiotics should be given within 1 h before incision and continued for 24 h postoperatively (antibiotic type dependent on local guidelines) Administer antibiotics at a minimum of 5 min before tourniquet inflation If cementation is required, should be antibiotic-impregnated |
| NSAIDs | Those with short half-lives (including ibuprofen) stop a minimum of 48 h prior; those with long half-lives (naproxen) stop within 3–7 days prior |
| PERIOPERATIVE FACTORS | |
| Theater | Keep theater door opening to a minimum |
| Personnel | Hand wash with antiseptic surgical solution, using a single-use brush or pic for the nails Before subsequent operations hands should be washed with either an alcoholic hand rub or an antiseptic surgical solution Double glove and change gloves regularly minimum at 2 h; change outer gloves when draping |
| Skin preparation | Use an alcohol prewash followed by a 2% chlorhexidine-alcohol scrub solution |
| Anesthetic | Maintain normothermia Maintain normovolemia A higher inspired oxygen concentration perioperatively and for 6 h postoperative may be of benefit |
| Drapes | Use of iodine-impregnated incise drapes may be of benefit (in patients without allergy) |
| Blood transfusion | Optimize preoperative hemoglobin If possible, transfusion should be avoided intraoperatively and, if anticipated, should be given more than 48 h before surgery Antifibrinolytics may indirectly reduce SSI by reducing the need for transfusion |
| POSTOPERATIVE FACTORS | |
| Dental procedures | Insufficient evidence to recommend the use of prophylactic antibiotics for patients undergoing routine dental procedures following joint replacement |
BMI , Body mass index; DMARDs, disease-modifying antirheumatic drugs; MRSA, methicillin-resistant Staphylococcus aureus ; MSSA, methicillin-sensitive S. aureus ; NSAIDs, nonsteroidal antiinflammatory drugs; SSI, surgical site infection; TNF , tumor necrosis factor.
Prophylactic antibiotic therapy
Many studies have shown the effectiveness of prophylactic antibiotics in reducing infection rates after orthopaedic procedures. During the first 24 hours, infection depends on the number of bacteria present. During the first 2 hours, the host defense mechanism works to decrease the overall number of bacteria. During the next 4 hours, the number of bacteria remains constant, with the bacteria that are multiplying and the bacteria that are being killed by the host defenses being about equal. These first 6 hours are called the “golden period,” after which the bacteria multiply exponentially. Antibiotics decrease bacterial growth geometrically and delay the reproduction of the bacteria. The administration of prophylactic antibiotics expands the golden period.
A prophylactic antibiotic should be safe, bactericidal, and effective against the most common organisms causing infections in orthopaedic surgery. Because the patient’s skin remains the major source of orthopaedic infection, prophylactic antibiotics should be directed against the organism most commonly found on the skin, which is S. aureus, although the frequency of Staphylococcus epidermidis is increasing. This increase in S. epidermidis is important because this organism has antibiotic resistance and often gives erroneous sensitivity data. Escherichia coli and Proteus organisms also should be covered by antibiotic prophylaxis. In the United States, first-generation cephalosporins (cefazolin weight adjusted, but a minimum of 2 g for patients weighing more than 70 kg and 3 g for patients weighing over 120 kg) have been favored for many reasons. They are relatively nontoxic, inexpensive, and effective against most potential pathogens in orthopaedic surgery. Cephalosporins are more effective against S. epidermidis than are semisynthetic penicillins. Clindamycin can be given if a patient has a history of anaphylaxis to penicillin. Routine use of vancomycin for prophylaxis should be avoided. If a patient has risk factors that predisposes to an infection, then weight-adjusted vancomycin (15 mg/kg, 1 g over 1 hour to avoid red man syndrome) may be added to the preoperative antibiotic protocol.
Antibiotic therapy should begin immediately before surgery (30 to 60 minutes before skin incision). A maximal dose of antibiotic (weight adjusted) should be given and can be repeated every 4 hours intraoperatively or whenever the blood loss exceeds 1000 to 1500 mL. Little is gained by extending antibiotic coverage over 24 hours, and the possibility of side effects, such as thrombophlebitis, allergic reactions, superinfections, or drug fever, is increased. Prophylactic antibiotics should not be extended past 24 hours even if drains and catheters are still in place. The current CDC recommends no additional antibiotics after skin closure. Namias et al. found that antibiotic coverage for longer than 4 days led to increased bacteremia and intravenous line infections in patients in intensive care units. Evidence now shows that 24 hours of antibiotic administration is just as beneficial as 48 to 72 hours. Currently, antibiotic prophylaxis for patients undergoing colonoscopy, upper gastrointestinal endoscopy, or dental procedures (even in patients with total joint arthroplasty) is not recommended. For current prophylaxis please visit www.orthoguidelines.org/auc . If antibiotics are to be used see Table 20.4 for recommended antibiotics and dosing.
Table. 20.4
Appropriate Prophylactic Antibiotics and Dosages
From, American Academy of Orthopaedic Surgeons Board of Directors and the American Dental Association Council on Scientific Affaris: Appropriate use criteria for the management of patients with orthopaedic implants undergoing dental procedures, 2016.
| Situation | Agent | Regimen—single dose 30–60 min before dental procedures | |
|---|---|---|---|
| Adults | Children | ||
| Oral | Amoxicillin | 2 g | 50 mg/kg |
| Unable to take oral medication | Ampicillin or ceftriaxone | 2 g IM or IV ∗ 1 g IM or IV |
50 mg/kg IM or IV 50 mg/kg IM or IV |
| Allergic to oral penicillins or ampicillin | Cephalexin † , ‡ or azithromycin or clarithromycin | 2 g 500 mg |
50 m/kg 15 mg/kg |
| Allergic to penicillins or ampicillin and unable to take oral medication | Ceftriaxone, ‡ azithromycin, clarithromycin | 1 g IM or IV Equivalent dose 500 mg IV |
50 mg/kg IM or IV Equivalent dose |
∗ Intramuscular injections should be avoided in persons receiving anticoagulants.
† Or other first-or second-generation oral cephalosporin in equivalent adult or pediatric dosage.
‡ Cephalosporins should not be used in an individual with a history of anaphylaxis, angioedema, or urticaria with penicillins or ampicillin.
Antibiotic irrigation has not found a definite role in orthopaedic surgery. Several studies have shown a decrease in colony counts in wounds and a decrease in infection rates with the use of antibiotic irrigation in general surgical procedures. When a topical antibiotic is used, it should have (1) a wide spectrum of antibacterial activity, (2) the ability to remain in contact with normal tissues without causing significant local irritation, (3) low systemic absorption and toxicity, (4) low allergenicity, (5) minimal potential to induce bacterial resistance, and (6) availability in a topical preparation that can be easily suspended in a physiologic solution. We have employed the recommendations of the CDC as well as the World Health Organization (WHO) in utilizing a dilute (sterile water not tap) povidone-iodine wound soak before closure to decrease SSI. We follow the recommendations of Brown et al., utilizing 17.5 mL of 10% povidone-iodine in 500 to 1000 mL sterile normal saline irrigation of the wound for 3 minutes. The wound is then irrigated with normal saline. This has led to a decrease in SSI from 0.97% to 0.15%. Although the numbers may appear small, the overall increase in surgeries (by 2030: TKA increase 673% and THA increase by 174%) will significantly reduce infections in individual patients. This solution should be avoided in patients who are allergic to iodine or when cartilage-sparing procedures are performed (i.e., unicompartmental knee replacements). In addition, when liposomal bupivacaine is used, the povidone-iodine solution should be applied before the bupivacaine because it is toxic to liposomes. We no longer routinely add antibiotics to our irrigation solutions. The use of powdered vancomycin sprinkled locally into the wound remains controversial. Hydrogen peroxide also is no longer recommended for wound irrigation because of its associated cytotoxicity, impaired wound healing, and oxygen embolic phenomenon.
The importance of irrigation and debridement in the treatment of open fractures has been well documented. The principles of elimination of devitalized tissue and dead space, evacuation of hematomas, and soft-tissue coverage also can be applied to “clean” orthopaedic cases.
Methicillin-Resistant Staphylococcus Aureus
The evolution of S. aureus into a multiple-drug–resistant pathogen, methicillin-resistant S. aureus (MRSA), has become a major health concern worldwide. Approximately 57% of S. aureus bacteria are methicillin resistant, and now vancomycin-resistant strains are being reported. This is probably one of the most worrisome problems in the fight against bacterial infections. Initially, MRSA was seen only in hospital settings and long-term care facilities; however, it is now becoming increasingly prevalent in young, healthy individuals in the community ( Table 20.5 ; At-Risk Groups). It has been estimated that 4% of the population in the United States are carriers of MRSA. It is particularly virulent, with a mortality rate of approximately 20%.
Table. 20.5
At-Risk Groups and Risk Factors for Community-Acquired Methicillin-Resistant Staphylococcus aureus
From Marcotte AL, Trzeciak MA: Community-acquired methicillin-resistant Staphylococcus aureus: an emerging pathogen in orthopaedics, J Am Acad Orthop Surg 16:98–106, 2008.
| At-Risk Groups | Risk Factors |
|---|---|
|
|
S. aureus infection in orthopaedic hospitalized patients generally is around 3%; however, over half of these patients have MRSA. Osteomyelitis caused by MRSA is an infrequent presentation, but treatment can be especially troublesome, and reports of subperiosteal abscess and necrotizing fasciitis also are increasing. Estimates of MRSA infection after total joint replacement range from 1% to 4%, and infection can occur up to 12 years after surgery. Kim et al. prospectively studied the feasibility of bacterial prescreening before elective orthopaedic surgery. They found that 22.6% of 7019 patients were S. aureus carriers and 4.4% were MRSA carriers. MRSA carriers had a statistically significantly higher rate of SSIs than methicillin-sensitive S. aureus (MSSA) carriers (0.97% compared with 0.14%; P = 0.0162). Although not statistically significant, MSSA carriers, approximately 30% of the United States population, also had higher rates of SSIs. After screening was initiated, the institutional infection rate dropped from 0.45% to 0.19% ( P = 0.0093). The cost-effectiveness of such screening programs has not been determined, although with the increasing prevalence of MRSA, these costs may be justified.
Approximately 3% of MRSA outbreaks have been attributed to asymptomatic colonized health care workers. Schwarzkopf et al. prospectively studied the prevalence of S. aureus colonization in orthopaedic surgeons and their patients and found that among surgeons and residents there was a higher prevalence of MRSA compared with a high-risk group of patients. Junior residents had the same prevalence of MRSA colonization as institutionalized patients, most likely because of the substantial time spent in direct patient care. These researchers recommended hand hygiene for the prevention of MRSA. In addition, universal decolonization of patients with mupirocin was recommended before total joint and spine surgeries, although further study of this practice is indicated. Skramm et al. proved that the S. aureus colonies that were isolated from operating personnel were indeed the same strain found at the SSI up to 85% of the time. No true proof exists that decolonization of MRSA carriers decreases SSI incidence. There is no definitive recommendation on screening and preoperative treatment of MRSA carriers. However, some advocate povidone-iodine nasal ointment, which would also ease fears of emerging resistance to mupirocin use.
Because of the prevalence of community-acquired (CA)-MRSA, it is necessary to rapidly identify the organism, determine antibiotic sensitivity, and begin antibiotic therapy (for empirical coverage see Table 22.3 ). Polymerase chain reaction (PCR) can be used to detect Staphylococcus with results within 24 hours as opposed to conventional cultures that can take 3 days before results are available. Vancomycin or teicoplanin should be considered in patients with colonization of MRSA or when screening results before surgery are not available. For invasive infections, intravenous vancomycin is recommended or, alternatively, daptomycin, gentamicin, rifampin, and linezolid can be used. In cases of necrotizing fasciitis, clindamycin, gentamicin, rifampin, trimethoprim-sulfamethoxazole, and vancomycin are effective. Rifampin should never be used alone as the single antibiotic. Until a sensitivity determination can be made, antimicrobial coverage specifically of CA-MRSA is recommended. For deep subperiosteal abscesses or superficial abscesses, irrigation and debridement are necessary to reduce bacterial counts. Overuse of quinolones may be driving the selection of MRSA over MSSA and should be avoided. Obtaining an infectious disease consult is highly recommended.
In summary, despite few direct evidence-based studies, best current efforts at controlling SSI are described in Table 20.3 .
Diagnosis
The diagnosis of infection may be obvious or obscure. Signs and symptoms vary with the rate and extent of bone and joint involvement. Characteristic features of fever, chills, nausea, vomiting, malaise, erythema, swelling, and tenderness may or may not be present. The classic triad is fever, swelling, and tenderness (pain). Pain probably is the most common symptom. Fever is not always a consistent finding. Infection may also be as indolent as a progressive backache or a decrease in or loss of function of an extremity. No single test is able to serve as a definitive indicator of the presence of musculoskeletal infection.
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