Transmission and Prevention of Occupational Infections in Orthopaedic Surgeons

1 Department of Orthopaedics and Traumatology, Chinese University of Hong Kong, 5/F, Clinical Science Building, Prince of Wales Hospital, Hong Kong Special Administrative Region, China. E-mail address for K.C. Wong: skcwong@ort.cuhk.edu.hk

Investigation performed at the Department of Orthopaedics and Traumatology, Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China

The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Abstract

Microorganisms are transmitted in hospitals mainly by contact, droplet, and airborne routes.

Orthopaedic surgeons have a substantial occupational risk of contracting a blood-borne infection because of frequent handling of sharp instruments and objects during operative procedures.

Aerosolization means the formation of aerosols and droplets when blood or other body fluids are mechanically disturbed. Smaller particles (<5 µm) will remain suspended in air. Pathogens that can survive in these small airborne particles may cause infection if they are inhaled.

Aerosol-generating procedures in patients with tuberculosis or severe acute respiratory syndrome (SARS) may facilitate airborne transmission.

The Hospital Infection Control Practices Advisory Committee and the Centers for Disease Control and Prevention have established guidelines for isolation precautions in hospitals.

Introduction

Surgeons and health-care workers have always had a high risk of exposure to blood-borne diseases as a result of their occupation. Orthopaedic surgeons have substantial occupational exposure to blood and the risk of blood-borne infection because of frequent handling of sharp instruments, metal objects (e.g., wire), and bone fragments during operative procedures1-4.

The purpose of this review is to discuss the risk of occupational blood-borne infection and the means of disease transmission by contact, droplet, and airborne routes in orthopaedic surgery. The role of aerosolization in the facilitation of disease transmission will be analyzed. Severe acute respiratory syndrome (SARS), the recently recognized and highly contagious respiratory infection, will be discussed in detail. Finally, precautionary measures to protect against occupational infection will be reviewed.

Means of Transmission of Microorganisms

Understanding the means of transmission of infectious diseases is very important in the prevention of occupational transmission of pathogens. Microorganisms are transmitted in hospitals mainly by contact, droplet, and airborne routes.

Contact Transmission

This is the most important and frequent mode of transmission of nosocomial infection. There are two types of contact transmission: direct and indirect. Direct-contact transmission involves direct body-to-body contact with the transfer of microorganisms during routine care of patients. Indirect-contact transmission is the transmission of pathogens by contact with contaminated objects such as dressings, needles, and instruments.

Droplet Transmission

Droplets are primarily generated by patients during coughing, sneezing, and talking and during the performance of certain procedures such as suctioning and bronchoscopy. Transmission occurs when droplets containing microorganisms generated from the infected patient are propelled a short distance through the air and deposited on the skin or mucosal surface of the health-care worker. Severe acute respiratory syndrome (SARS) is one of the illnesses transmitted by droplets, and it has spread worldwide and raised global concern.

Airborne Transmission

Aerosolization means the formation of aerosols and droplets when blood or another body fluid is mechanically disturbed. Small particles (<5 µm) can remain suspended in air and can be dispersed widely by air currents. Airborne transmission can occur by dissemination of these small particles if they contain pathogens, and inhalation of these particles may result in infection. Mycobacterium tuberculosis is an example of a typical microorganism transmitted by this airborne route.

Contact Transmission

Health-care workers and particularly surgeons are at risk for occupational transmission of blood-borne pathogens, such as hepatitis-B virus, hepatitis-C virus, and human immunodeficiency virus (HIV). Infection with blood-borne pathogens occurs mainly by contact transmission—i.e., percutaneous or mucocutaneous exposure to blood-borne pathogens. Percutaneous exposure is due to needlesticks or cuts from other sharp instruments, implanted materials, or bone fragments contaminated with the blood of infected patients. Mucocutaneous exposure occurs through contact of the mucous membrane of the eyes, nose, or mouth or contact of the skin with the blood of infected patients. Percutaneous injuries are a substantial risk for health care workers, with 5520 percutaneous injuries reported by fifteen hospitals participating in the Centers for Disease Control and Prevention National Surveillance System for Hospital Health Care Workers (NaSH) between June 1995 and July 19995. Of 4569 percutaneous injuries, 2826 (62%) were associated with hollow-bore needles5. Of 3057 percutaneous injuries, approximately 38% occurred during use of needles and 42% occurred after use and before disposal of needles5.

The risk of percutaneous and mucocutaneous exposure for orthopaedic surgeons and operating room personnel has also been investigated. Gerberding et al.3 discussed the risk of exposure to blood at San Francisco General Hospital after analyzing data on 1307 consecutive operations. They found that percutaneous injury occurred in twenty-two operations (1.7%) and mucocutaneous exposure occurred in sixty-two (4.7%). The risk of exposure was higher when procedures lasted more than three hours and blood loss exceeded 300 mL.

Quebbeman et al.4 studied the prevalence of percutaneous injuries and mucocutaneous exposure during 234 operations involving 1763 operating room personnel. They found that percutaneous injuries occurred in thirty-five operations (15%) and mucocutaneous exposure, in 118 (50%). In addition, orthopaedic surgeons had increased face and neck contamination due to splattering of blood from power tools and the use of irrigation fluids.

In a study in which a mail survey was sent to 1200 orthopaedic surgeons in the United Kingdom and 800 (67%) responded, 511 surgeons reported that they had sustained needlestick injuries or contamination of the eyes with patients' body fluid within the past month6.

In another investigation, orthopaedic surgeons attending the annual meeting of the American Academy of Orthopaedic Surgeons in 1991 were surveyed about occupational blood contact and HIV infection2. Of 7147 orthopaedic surgeons at the meeting, 3420 (47.9%) participated in the survey; 2989 (87.4%) reported cutaneous contact with blood and 1340 (39.2%) reported percutaneous contact with blood in the previous month. One hundred and nine surgeons (3.2%) reported percutaneous contact with the blood of a patient known to have HIV infection or acquired immunodeficiency syndrome (AIDS) in their career. Among 108 participants with nonoccupational HIV risk factors, only two were positive for the HIV antibody. Among 3267 participants without nonoccupational HIV risk factors, none was positive for the HIV antibody.

Surgeons sustain most percutaneous injuries when they are suturing. The index finger of the nondominant hand is often injured because of the surgeon's use of his or her fingers to hold tissue while suturing or during blind suturing7,8.

The occupational risk of infection with blood-borne pathogens depends on a variety of factors9 as presented in Table I.

TABLE I Factors That Affect the Risk of Occupational Infection with Blood-Borne Pathogens

Prevalence of pathogens in the patient population

Amount of pathogens in the blood of the patient at the time of exposure

Type of pathogens

Incidence of percutaneous or mucocutaneous exposure

Type and severity of percutaneous injuries; i.e., whether the injuries were caused by a solid-bore needle, a hollow-bore needle, a scalpel, or another instrument. (A laboratory experiment demonstrated that more blood is transferred by deeper injuries and hollow-bore needles97. Therefore, the risk is higher with hollow-bore needles and deeper injuries than it is with solid-bore needles and superficial injuries.)

Availability and use of preexposure vaccination and postexposure prophylaxis (i.e., treatment for prevention of disease once exposure has occurred)

Hepatitis-B Virus

The risk of transmission of hepatitis-B virus during a single percutaneous exposure of an unvaccinated person to blood infected with the virus ranges from 6% to 30%10,11. The risk associated with mucocutaneous exposure has not been quantified but may be higher than the risk with other blood-borne pathogens. Hepatitis-B virus can survive in dried blood at room temperature on environmental surfaces for at least one week12. The potential for transmission of hepatitis-B virus through contact with environmental surfaces has been demonstrated in investigations of outbreaks of infections with hepatitis-B virus among patients and staff of hemodialysis units13,14. Hepatitis-B virus has been found in saliva but is usually undetectable in urine and feces15. Transmission of the virus by human bites is therefore possible and has been documented16. The risk of infection after exposure depends on the status of the hepatitis-Be antigen of the source individual. The presence of hepatitis-Be antigen in the serum is associated with higher levels of circulating virus in the blood and therefore with greater infectivity of an individual who is positive for the antigen11.

Vaccination against hepatitis B is a safe and effective way to prevent hepatitis-B infection. It is strongly recommended that all surgeons receive the vaccine. Testing for antibody response should be completed one to two months after the third vaccine dose. A protective antibody response is 10 mIU/mL. Vaccine-induced hepatitis-B surface antibodies decline gradually over time17. However, immune memory remains intact indefinitely following immunization, and people with declining levels of hepatitis-B surface antibodies are still protected against the disease18. Therefore, neither booster doses of hepatitis-B vaccine nor periodic testing for hepatitis-B surface antibodies is necessary for previously immunized surgeons19. The hepatitis-B vaccination status and the vaccine-response status of the exposed surgeon will aid in determining appropriate postexposure prophylaxis. The mainstay of postexposure prophylaxis is hepatitis-B vaccine, but in some settings the addition of hepatitis-B immunoglobulin provides better protection. Table II summarizes the recommendations of the Centers for Disease Control and Prevention for postexposure prophylaxis after parenteral exposure to hepatitis-B virus.

TABLE II Recommended Postexposure Prophylaxis Following Parenteral Exposure to Hepatitis B Virus

A nonresponder is a person with an inadequate antibody response to hepatitis-B virus vaccine (hepatitis-B surface antibodies < 10 mIU/mL). The option of giving one dose of hepatitis-B immunoglobulin and reinitiating the vaccine series is preferred for nonresponders who have not completed a second three-dose vaccine series. The option of two doses of hepatitis-B immunoglobulin is preferred for persons who previously completed a second vaccine series but did not respond to it. A responder is a person with an adequate protective antibody response to hepatitis-B virus vaccine (hepatitis-B surface antibodies 10 mIU/mL).

Hepatitis-C Virus

The prevalence of anti-hepatitis-C virus seroconversion (an indication of infection) after an accidental percutaneous exposure to blood infected with the virus averages 1.8% and ranges from 0% to 7%20. The prevalence is lower than that associated with exposure to hepatitis-B virus. Transmission rarely occurs from exposure of the mucous membrane to blood. We are aware of only two case reports demonstrating transmission of hepatitis-C virus following occupational conjunctival exposure to blood21,22. To our knowledge, transmission of hepatitis-C virus during exposure of intact or nonintact skin to the blood of patients with hepatitis-C virus infection has never been documented. In addition, hepatitis-C virus RNA has not been detected in the urine, feces, or saliva from patients with chronic hepatitis-C virus infection23. The risk of transmission of hepatitis-C virus during exposure to the above secretions has not been quantified but is expected to be low. Currently, neither vaccines nor medications for postexposure treatment are available to prevent hepatitis-C virus infection.

Human Immunodeficiency Virus (HIV)

The risk of HIV infection due to a single percutaneous injury is estimated to be 0.3% (95% confidence interval = 0.2% to 0.5%)24,25. It is higher than the estimated risk of infection after exposure of a mucosal membrane (0.09%) (95% confidence interval = 0.006% to 0.5%)26. Transmission of HIV due to exposure involving small amounts of blood on intact skin has not been documented, to our knowledge. In one prospective study of 2712 cases of exposure of intact skin to HIV, no infections were found27. Therefore, a small amount of HIV on intact skin probably poses no risk. In one case-control study of health-care workers who had percutaneous exposure to HIV, the risk of HIV infection was shown to increase with exposure to a larger amount of HIV-infected blood28. Four factors were also found to be associated with an increased risk of HIV transmission in that study: (1) deep injury, (2) visible blood on the device that caused the injury, (3) a procedure that involved a large-gauge hollow-bore needle directly placed in a vein or artery, and (4) exposure to a patient with acquired immunodeficiency syndrome or a high plasma viral burden28.

HIV has been found in the saliva from some AIDS patients, although in lower quantities than in the plasma29. HIV has not been recovered from the sweat of HIV-infected persons. The risk of transmission through exposure to these fluids is probably considerably lower than the risk with exposure to HIV-infected blood27. The relative infectivity of HIV varies among individuals and over time for a single individual30. Unlike the case for hepatitis-B virus infection, there is currently no readily available laboratory test with which to assess increased HIV infectivity.

Although medications for postexposure prophylaxis against HIV infection are available, data regarding their efficacy are limited. Zidovudine (azidothymidine [AZT]), a nucleoside analogue reverse transcriptase inhibitor, is the only drug that has been studied and shown to reduce the risk of HIV transmission following occupational exposure. A retrospective case-control study on health-care workers revealed an 81% (95% confidence interval = 48% to 94%) reduction in the risk of infection with the use of AZT after percutaneous exposure28. However, a combination of antiviral medications, rather than a one-drug AZT regimen, is now recommended (based on data derived from treatment of HIV-infected patients) for its theoretical advantage of more effective prevention of HIV transmission31. The Centers for Disease Control and Prevention (CDC) recommended a basic two-drug regimen of AZT and lamivudine when there is a risk of infection. A three-drug regimen, with the addition of a protease inhibitor such as indinavir, is recommended when there is a higher risk of transmission31. All of these antiviral drugs are potentially toxic and have been associated with side effects. As most instances of occupational exposure to HIV do not result in HIV transmission, the risks and benefits of prescribing postexposure prophylaxis must be carefully considered.

Droplet and Airborne Transmission

Tuberculosis is a respiratory infection caused by Mycobacterium tuberculosis and is spread by airborne transmission. The SARS virus is predominantly spread by droplets shed from respiratory secretions of infected individuals. Although airborne transmission does not seem to be a major route for the spread of the SARS virus, there have been anecdotal reports that aerosol-generating procedures might facilitate transmission of the virus in some cases32. As a result, it is crucial to understand the role of aerosolization of body fluids in facilitating disease transmission.

Aerosolization

Aerosols are defined as fine particles with a diameter of 10 µm that are suspended in a gas. Droplets are much larger particles that have a definite trajectory pathway away from the site of production33. Aerosols and droplets can be formed when blood or another body fluid is mechanically disturbed. They are thus generated by some patients during coughing and sneezing; they can also be generated by the use of pulsed irrigation or power tools during operative procedures. The more violent the disturbance, the more likely is the formation of aerosols and smaller droplets. Larger particles (5 µm in diameter) settle rapidly under gravity, whereas smaller particles (<5 µm in diameter) settle slowly and remain in the air.

If a suspension of microorganisms is aerosolized, the liquid component will dry up rapidly, leaving the microbial contents as droplet nuclei suspended in air. These droplet nuclei containing microorganisms, usually referred to as infected airborne particles, can be dispersed by air currents generated by ventilation or movement of people and can reach a long distance from an infected source. Particles of <5 µm in diameter are more likely to reach the alveoli of the lung than are larger particles, which tend to be trapped in the upper respiratory tract. Therefore, airborne transmission can occur by dissemination of these infected airborne particles if a susceptible host inhales them. Contact transmission of infection may also occur if these aerosols come into contact with mucous membranes or small wounds34. Thus, special air handling and ventilation are required to prevent this airborne infection.

Droplets generated from infected persons do not travel far, usually 3 ft (0.9 m) in air, and are deposited on environmental surfaces or on the skin or mucous membranes of individuals. Any pathogens that can survive in these droplets pose a risk of infection.

Mucocutaneous exposure due to droplet transmission should not be confused with airborne transmission by aerosols35 because droplets do not remain suspended in air. Special air handling or ventilation is thus not required to prevent droplet transmission.

Particles of various sizes are produced during coughing and sneezing. Pathogens capable of surviving in small droplet nuclei (<5 µm in diameter) then become airborne. To be capable of surviving in small droplet nuclei, the pathogen must be durable and resistant to drying. Therefore, when a patient with tuberculosis coughs, he or she spreads the disease by the airborne route. When a patient with influenza coughs, he or she spreads the disease by droplet transmission. SARS is thought to spread predominantly by droplet transmission.

Although it is known that blood-borne pathogens can be transmitted through mucous membrane exposure, there is a lack of evidence suggesting that blood-borne pathogens can be transmitted by inhalation of aerosolized blood. Hepatitis-B virus infection is not transmitted by inhalation of aerosolized blood36,37. However, studies have shown that common orthopaedic power tools are capable of generating respirable blood containing aerosols38-40. These aerosols can be spread all over the operating room, contaminating the animate and inanimate environmental surfaces39. A study in which cascade impactors were mounted in the breathing zones of primary and assistant surgeons demonstrated that the surgeons were exposed to respirable blood containing aerosols in the operating rooms41. An experimental study demonstrated that HIV can remain viable in cool aerosols generated by power tools42. This may cause HIV transmission to surgeons exposed to aerosols generated during operations on HIV-infected patients. Therefore, aerosolized blood-borne pathogens may lead to airborne infection if the aerosols containing the pathogens are inhaled. Additional work is required to determine whether this aerosol amounts to a significant occupational risk in operating theaters.

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Precautionary measures against contact with infectious aerosols and droplets have to be mandatory during procedures in which high-speed orthopaedic power tools are used. Every person present during the surgery should wear personal protective apparel, including surgical gloves, a water-resistant surgical gown with long sleeves, a surgical mask, and full-face protection with a face-shield. Additional respiratory protective equipment should be used when surgeons operate on patients with tuberculosis or SARS. It is recommended that the surgery be performed by experienced surgeons and anesthetists and sufficiently trained personnel to reduce operative time and the duration of exposure to infectious aerosols. Use of diathermy and power tools should be kept to a minimum. Wound irrigation with bulb syringes is preferred to pulsed irrigation. It is critical to remove and dispose of protective apparel and respiratory devices without contaminating oneself at the conclusion of the procedure. It is essential to wash the hands prior to touching the face, eyes, or nose after removal of protective apparel. Most operating rooms undergo up to twenty room-air exchanges per hour. Therefore, any infectious aerosol particles should be removed quickly. However, the entire operating theater must be properly decontaminated between cases, as pathogens within droplets can survive for hours outside the body on inanimate environmental surfaces.

Tuberculosis

Tuberculosis is the prototype disease for the study of airborne infection because it is transmitted effectively through the air when people in close contact with a person with active disease inhale droplet nuclei containing tubercle bacilli (1 to 5 µm in diameter).

Investigations of outbreaks of tuberculosis can illustrate several important principles of disease transmission. One study showed that inadequate ventilation resulted in recirculation of contaminated air and positive tuberculin conversion in 35% of sixty employees43. Tuberculosis may also spread through inhalation of aerosols generated during the care of a tuberculous skin lesion44 or during procedures such as irrigation of tuberculous abscesses of the hip and thigh with saline solution45. These cases demonstrated that nonpulmonary tuberculosis could also be contagious in certain settings. Other aerosol-generating procedures such as nasotracheal suctioning can amplify the risk of transmission, as shown by an outbreak in an emergency room, where an intubated man was present for only four hours and spread infection to at least sixteen of the 112 emergency room staff46. Managing unsuspected cases of tuberculosis also results in a higher risk of tuberculin conversion47. Early identification and a high index of suspicion of the disease are essential for preventing the disease.

Severe Acute Respiratory Syndrome (SARS)

SARS is a newly recognized, severe febrile respiratory illness caused by a previously unknown coronavirus, SARS-associated coronavirus (SARS-CoV). The condition primarily affects people who come into close contact with infected patients as well as health-care workers who look after the patients. This highly contagious respiratory infection can affect healthy people and can frequently result in rapid deterioration and progress to respiratory failure. It is also a potentially fatal disease. In an epidemiological study of 1425 patients with SARS, the mortality rate was reported to range from 13.2% for patients younger than sixty years of age to 43.3% for those older than sixty years of age48. SARS was spread worldwide to thirty countries by travelers in 2003, prompting the World Health Organization to issue a global alert for the first time in more than a decade.

The primary mode of spread is by droplet transmission. It occurs when individuals come into close contact with contaminated respiratory droplets that were shed from secretions of an infected person during coughing or sneezing49. SARS-CoV can be found in urine and feces from infected individuals50. New evidence suggests that the virus survives in feces and urine at room temperature for at least one to two days. Heating to 56°C kills the virus, as does exposure to many commonly used disinfectants51. SARS-CoV can thus be transmitted if people touch their own mucous membrane with their contaminated hands. Blood can also contain SARS-CoV, and viremia has been detected up to ten days after the onset of symptoms in patients with SARS52. There is a theoretical risk that SARS-CoV can behave like other blood-borne pathogens and spread the disease by contact transmission. However, we are not aware of any study in which this possibility was investigated. More work is required to determine whether this means of transmission of SARS actually exists.

Originally, SARS was not thought to spread by the airborne route. However, the outbreak in Hong Kong that originated at the Metropole Hotel53 and the Amoy Gardens54 indicates that airborne transmission is possible in special settings. Aerosolization of body fluids of an infected person may facilitate the transmission. However, there is a lack of evidence suggesting that SARS can be transmitted secondarily by aerosolization of blood.

It has been shown that the viral load in the nasopharyngeal aspirates of SARS patients does not peak until ten days after the onset of symptoms. At fifteen days, it decreases to the levels measured during the initial presentation to the hospital (mean, 3.2 days after the onset of symptoms). In the stool, the viral load appears to peak at fourteen days after the onset of symptoms50. The infectivity of SARS-CoV might be variable over time, even during the symptomatic phase of the disease, and transmission may be more likely during the later stages of the disease.

The World Health Organization categorizes SARS into suspected and probable cases according to the case definition55. In brief, the case definition of SARS includes a fever of 38°C during the two days before presentation; coughing, shortness of breath, malaise, or headache; new pulmonary infiltrates on chest radiographs or high-resolution computed tomography scans; a history of contact with an infected person; absence of an alternative diagnosis to explain the clinical presentation; and laboratory evidence of SARS-CoV infection. Therefore, SARS is diagnosed according to clinical and radiographic features, contact history, and laboratory tests. However, existing reverse transcriptase-polymerase chain reaction (RT-PCR) tests for SARS-CoV are not very accurate, especially during the early phase of the disease when the viral load is low. The positivity of the test thus depends on the timing of the collection of the specimens. Interpretation of these assays must be performed carefully because of the possibility of false-negative results, which are frequent early in the course of the infection, and false-positive results, which are especially important concerns. Existing antibody tests of seroconversion are generally useful only after three weeks have elapsed following the disease onset, which is far too late to be of much practical use. Therefore, in the absence of a reliable and rapid laboratory test, the diagnosis of SARS is based purely on clinical and radiographic features and a positive contact history.

This may cause some difficulties in identifying SARS, particularly in geriatric patients. Early symptoms of SARS such as fever, malaise, and headache are nonspecific and are associated with other, more common illnesses. Frail elderly patients with multiple coexisting chronic diseases might have no fever at presentation56,57, leading to a delay in diagnosis. Therefore, the initial diagnosis depends largely on a history of exposure risk. However, geriatric patients may not be able to provide a precise contact history. Also, some patients may be reluctant to reveal a true contact history because of a fear of social stigma or quarantine of their families or friends58.

In the presence of infection, frail geriatric patients tend to have a history of falls, confusion, incontinence, and poor feeding at presentation. Focus on the management of injuries or fractures resulting from falls by geriatric patients may distract orthopaedic surgeons from investigating the medical cause of the injury, such as SARS59. Identification of SARS in this group thus requires a high index of suspicion. Unrecognized cases of SARS may lead to future outbreaks60.

No vaccines have yet been developed and no antiviral treatment has been shown to be effective against SARS. Success in controlling disease transmission relies on early identification of suspected cases, proper isolation, and implementation of and adherence to infection control precautions61.

Prevention of Occupational Infection Among Orthopaedic Surgeons

The Hospital Infection Control Practices Advisory Committee (HICPAC) and the Centers for Disease Control and Prevention have established guidelines for isolation precautions in hospitals62. Because pathogens and host factors are sometimes more difficult to eliminate, a more feasible way of controlling the spread of disease is by taking isolation precautions to interrupt the spread directly at the level of transmission.

There are two tiers of HICPAC Isolation Precautions. The first tier is Standard Precautions. They are designed for the care of all inpatients, irrespective of their underlying diseases or presumed infection status. Blood and all other body fluids of patients are considered to be potentially infectious. The second tier is Transmission-Based Precautions. They are used for patients known or suspected to be infected or colonized with transmissible or epidemiologically important pathogens for which additional precautions beyond Standard Precautions are required to prevent nosocomial transmission. Transmission-Based Precautions are based on the knowledge of routes of transmission. They are classified as Contact Precautions, Droplet Precautions, and Airborne Precautions. The precautions may be combined for diseases that have multiple modes of transmission such as SARS. They are also expected to be used in addition to Standard Precautions.

While it is impossible to apply Transmission-Based Precautions to all patients, early identification of certain infectious diseases that warrant the additional use of these enhanced precautions is crucial. The risk of transmission of infection will certainly be minimized if precautions based on the diagnosis of infectious diseases can be implemented early.

As a result, Standard Precautions should be applied whenever there is a risk of exposure to blood or other body fluids of any patient. Contact Precautions should also be taken when health-care workers are caring for patients with blood-borne pathogens, and Droplet or Airborne Precautions should be added when they are dealing with patients with a disease such as SARS or tuberculosis.

A summary of Standard Precautions is provided in Table III. The reader is referred to the Centers for Disease Control and Prevention for complete recommendations with regard to both Standard and Transmission-Based Precautions62.

TABLE III Summary of Standard Precautions

Take care to prevent injuries when handling sharp instruments and needles; carefully dispose of all sharp devices; do not recap needles or use one-handed scoop technique; use mouthpieces, resuscitation bags, or other ventilation devices as an alternative to mouth-to-mouth resuscitation

Patient placement

Place patients who contaminate the environment or who do not assist in maintaining appropriate hygiene in a private room

The following sections will address the important issues pertinent to dealing with infectious diseases in orthopaedic practice. Only salient features of the Standard Precautions and Transmission-Based Precautions will be highlighted.

Hand-Washing

Hand-washing is the single most important and simplest step taken by surgeons to prevent disease transmission. It must be actively reinforced. Hand antisepsis reduces the incidence of nosocomial infection63-65. A recent study showed that increased hand-washing by hospital personnel reduced the acquisition of various health-care-associated pathogens65. Both this study and another66 showed that the prevalence of infection decreased as adherence to hand hygiene measures improved.

Studies have also indicated that scrubbing for five minutes reduces bacterial counts as effectively as does scrubbing for ten minutes67,68. Scrubbing for two to three minutes could reduce bacterial counts to acceptable levels as well69,70.

Protocols for hand antisepsis for surgical personnel have required scrubbing with a brush. However, the use of a brush may cause skin damage and lead to shedding of bacteria from the hands. Studies have also demonstrated that a brush is not necessary to reduce bacterial counts on the hands of surgical personnel to acceptable levels71-73. Therefore, brushes may do more harm than they contribute to cleaning. Their use should be restricted to cleaning the fingernails only.

Clinical trials have compared the effect of hand-washing with plain soap and water with the effect of some form of hand antisepsis on infection rates. Nosocomial infection rates were lower when antiseptic hand-washing was performed by hospital personnel74,75.

An alcohol-based surgical hand-rub is effective for hand antisepsis76-78. In one prospective, randomized trial of 4387 consecutive operations, hand rubbing with aqueous alcoholic solution preceded by a one-minute nonantiseptic hand wash was shown to be as effective as a traditional surgical hand-scrub with antiseptic soap (4% povidone iodine or 4% chlorhexidine gluconate) in preventing surgical site infection76. The authors concluded that hand rubbing with liquid aqueous alcoholic solution can be used safely as an alternative to the traditional surgical hand scrub. In another study, alcohol preparations were even more effective than povidone-iodine or chlorhexidine for the surgical scrub77. As a result, the presurgical scrub has been replaced in many European countries by the alcoholic rub. Table IV summarizes the characteristics of common hand antiseptic agents.

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TABLE IV Summary of the Characteristics of Common Antiseptic Agents78,98,99

* A score of +++ = excellent, ++ = good, + = fair, and - = poor. All agents are effective against enveloped viruses, which include hepatitis-B virus, hepatitis-C virus, HIV, and coronavirus. Residual activity increases with addition of a low concentration (0.5% to 1%) of chlorhexidine.

The Healthcare Infection Control Practices Advisory Committee and the Hand Hygiene Task Force of the Centers for Disease Control and Prevention have given the following recommendations for surgical hand antisepsis79:

Remove debris from underneath the fingernails with use of a nail cleaner under running water.

Perform hand antisepsis with use of either an antimicrobial soap or an alcohol-based hand-rub that has persistent activity before performing surgical procedures.

Scrub hands and forearms for the length of time recommended by the manufacturer of the hand cleaner, usually two to six minutes. Long scrub times (e.g., ten minutes) are not necessary.

Before applying an alcohol-based surgical hand-scrub product with persistent activity, prewash hands and forearms with a non-antimicrobial soap and dry hands and forearms completely. After applying the alcohol-based product as recommended, allow hands and forearms to dry thoroughly before donning sterile gloves.

Gloves

Wearing gloves is fundamental to both Standard and Transmission-Based Precautions. Gloves provide barrier protection to surgeons and reduce the risk of exposure to blood-borne pathogens as recommended by the Occupational Safety and Health Administration (OSHA)80. In the 2002 Cochrane Database Systematic Review of double gloving, the findings from eighteen randomized, controlled trials showed that double gloving reduces surgical cross infection. Wearing a glove liner between two pairs of latex gloves or wearing cloth outer gloves to perform joint replacement surgery decreases perforations to the innermost gloves more than does the use of double latex gloves81. One biomechanical study comparing double latex gloves with single latex orthopaedic gloves indicated that double gloves might be a desirable alternative to single orthopaedic gloves82. The most common concern that surgeons have about wearing double gloves is loss of touch sensitivity. Watts et al. found a significant difference (p < 0.05) in tactile sensation when similar pressure was applied by surgeons wearing single or double gloves83. However, the authors of the study concluded that this difference could be minimized by applying firmer pressure when wearing double gloves.

Masks, Protective Eyewear, and Face-Shields

Masks, eye protection, and face-shields are essential Contact and Droplet Precautions. They form an effective barrier that protects surgeons from exposure to infectious droplets and splashes. Eye protection is critical for orthopaedic surgeons because of the frequent use of power tools, which spray body fluid. In a prospective study of conjunctival contamination during common orthopaedic operations, forty-three (65%) of sixty-six goggles worn by surgeons were contaminated. The contamination rate of the protective flaps at the sides of the goggles was relatively low (5%), suggesting that ordinary spectacles, which are more convenient and comfortable than standard goggles, provide adequate protection during routine use84. Therefore, orthopaedic surgeons working in a high-risk environment must protect themselves against possible conjunctival contamination by wearing a mask with eye protection, goggles, or a face-shield or by minimizing the spraying of body fluid in the operating theater during the use of power tools.

Gowns

Sterile surgical gowns are used to create a barrier between the surgical field and potential sources of bacteria. They reduce wound contamination and clinical infection rates in clean surgery85. It has been estimated that, in joint replacement operations, 98% of bacteria found in patients' wounds come directly or indirectly from the air in the operating theater86. Studies have compared the effectiveness of occlusive clothing with that of body exhaust suits in reducing airborne bacterial contamination during joint replacement operations87-89. Body exhaust suits did not reduce the airborne bacterial contamination in the operating theater significantly more than did occlusive clothing (p > 0.05).

Different types of surgical occlusive clothing can offer different degrees of barrier protection to surgeons. Surgical gown fabrics with higher water and oil repellency and smaller pore sizes generally provide greater barrier protection90. In one comparative study, the amount of blood strike-through and bacterial penetration was lower with polypropylene disposable surgical gowns than it was with polyester-wood pulp disposable gowns or reusable, cotton gowns91.

Body exhaust suits or air exhaust systems with portable high-efficiency particulate filters are designed to protect patients from contamination by surgical teams. They can protect surgeons only against pathogens spread by contact or droplet transmission, not against those spread by airborne transmission. Additional respiratory protective equipment should be worn if there is a risk of airborne infection.

Strategies to Prevent Airborne Infection with Tuberculosis

The concept of reducing the risk of occupational exposure to airborne transmission of tuberculosis has evolved into three levels of control: administrative, engineering, and personal respiratory protection92.

The most important component is administrative control, which affects the largest number of persons. This involves implementation of administrative measures, such as maintaining a high index of suspicion, rapid identification, isolation, diagnostic evaluation, and treatment of the disease.

The second level of control is the use of environmental or engineering procedures, which eliminate the risk of exposure to health-care workers without reliance on their efforts. Examples include negative-pressure isolation rooms with more than twelve air exchanges per hour to remove potentially infected air from the environment, air cleaning with use of high-efficiency particulate air filters, or ultraviolet germicidal irradiation.

The last level is the use of personal respiratory protection equipment. On a hospital-wide basis, it is less effective than administrative and engineering control because respiratory protection can only reduce, not eliminate, the risk in the few areas where exposure to tuberculosis can still occur (e.g., rooms in which patients with known or suspected tuberculosis are being isolated and treatment rooms in which cough-inducing or aerosol-generating procedures are performed on such patients). These strategies also provide guidelines for dealing with other diseases with possible airborne transmission, such as SARS.

Personal Respiratory Protective Equipment

Surgical Masks

Surgical masks (Fig. 1) are generally worn by health-care workers to provide protection against pathogens spread by droplet transmission. However, they provide inadequate respiratory protection against pathogens with airborne transmission or during high-risk procedures that generate aerosols. They may have up to 50% filter leakage and are not sufficiently tight-fitting to prevent inhalation of aerosols. Therefore, they can provide protection only against larger droplets93,94.

Fig. 1 Surgical mask

N95 Respirators

An N95 respirator (Fig. 2) or an equivalent or higher-standard respirator should be worn for all contact with patients with tuberculosis or SARS. N95 respirators are air-purifying respirators, which protect against pathogens with droplet or airborne transmission. They fulfill the filtering efficiency criteria of the National Institute for Occupational Safety and Health (NIOSH) N95 standard. They are capable of filtering with at least 95% efficiency both larger droplets and most penetrating aerosols of 0.3 µm in diameter95. Air-purifying respirators require the user to generate negative pressure to "suck air through" the filtering material of the respirators. Facial hair prevents a good seal as will use of the wrong size of respirator. Before one of these respirators is used, it should be fit-tested according to the manufacturer's recommendations. Users should also check the fit of the respirator every time they wear them by placing both hands over the respirator and exhaling vigorously to determine if the respirator seals tightly to the face. Users should replace the respirator immediately if breathing becomes difficult, the respirator becomes damaged, or a proper face fit cannot be maintained. Respirators can be worn for six to eight hours continuously before being replaced. The outer surface should not be touched, and it must be replaced if it becomes grossly contaminated or wet. Models with exhalation valves should not be used in areas where a clean or sterile field is required.

Fig. 2 N95 respirator

Powered Air-Purifying Respirators

Nonoperative contact with patients with tuberculosis or SARS can be made with use of an N95 respirator, but an invasive procedure or an aerosol-generating procedure on such patients requires use of a highly protective respirator such as a powered air-purifying respirator (Fig. 3). It has been shown that, when a patient with tuberculous infection underwent a procedure that generated respiratory aerosols, operating personnel had to wear a powered air-purifying respirator in order to provide sufficient respiratory protection96. The Centers for Disease Control and Prevention recommended that the same principle be applied to patients with SARS32. At this time, there is inadequate information to determine whether this enhanced respiratory protection will reduce the transmission of SARS.

Fig. 3 Power air-purifying respirator. The respirator has a motor-driven fan that draws contaminated room air into a high-efficiency particulate air (HEPA) filter with a 99.97% filtering efficiency. The purified air is then delivered under positive pressure to the hood by means of a snap-in hose connector that is secured into the back of the hood. An N95 respirator is worn underneath the powered air-purifying respirator to provide maximum protection and protect the sterile surgical field from the respiratory secretions of the user.

In view of the possible airborne transmission of infectious aerosols from patients with tuberculosis or SARS, all operating room personnel should wear a powered air-purifying respirator with a hood that covers the head, neck, and shoulder regions during high-risk aerosol-generating procedures. The powered air-purifying respirator has a motor-driven fan that draws contaminated room air into a high-efficiency particulate air (HEPA) filter with a 99.97% filtering efficiency. The purified air is then delivered under positive pressure to the hood by means of a snap-in hose connector that is secured into the back of the hood. The exhaled air of the user escapes at the lower end of the hood, which is covered by an overlying waterproof gown. An N95 respirator is worn underneath the powered air-purifying respirator to provide maximum protection and protect the sterile surgical field from the respiratory secretions of the user.

Operating personnel should be trained and rehearsed on how to use the respiratory protective devices correctly because improper use will lead to a false sense of security. Dizziness or claustrophobia may be experienced when wearing a powered air-purifying respirator.

Overview

Orthopaedic surgeons are frequently exposed to blood and are at a high risk for blood-borne infection. The SARS outbreak has alerted us to the need for reviewing our current practices of infection control. Understanding the means of transmission of infectious diseases is very important in preventing occupational transmission of pathogens. There is a concern about secondary infection by aerosolization of blood or other body fluids during the use of power tools. Epidemiological studies on the risk of this means of transmission will be very difficult because of the need to control all risk factors in order to establish the relative infectivity of the patients compared with that of a control group not generating aerosols. Because of this current uncertainty, extra precautions should be adopted during aerosol-generating procedures.

Acknowledgments

NOTE: The authors acknowledge the help of Dr. Henry Ho for his work in editing the manuscript.

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