Infection in Patients after Implantation of an Orthopedic Device

Abstract

During the last several decades, the use of appropriate antibiotics has significantly improved our ability to prevent and treat infection that occurs after implantation of an orthopedic device. Despite improved prevention and treatment of this condition, patients who develop an infection secondary to implantation of an orthopedic device face increased mortality, morbidity, and/or delayed recovery. The presence of an orthopedic device significantly reduces the number of bacteria required to produce colonization and decreases the ability of the body’s own defense mechanism and antibiotics to resolve this condition. Efforts devoted to prevention of infection are much more effective than those spent treating the condition once it has developed. Pretreatment of patients with antibiotics and the use of ultra clean surgical rooms have been shown effective. Prevention will become increasingly important as antibiotic resistant strains of bacteria become more prevalent and the number of arthroplasty procedures performed also increases.

There are two general types of orthopedic devices that are implanted. First, hardware such as plates, screws, rods, and wires are used for the fixation of fractures. Second, prostheses are implanted to replace joints that are damaged due to deterioration or trauma. The largest and most commonly implanted are hip and knee replacement prostheses, referred to as total hips and total knees. ¹ This review will focus on joint replacement prostheses.

The incidence of infection after the implantation of orthopedic devices is low, ranging from approximately 1% in primary cases to 3% in secondary procedures. This relatively low infection rate is the result of modern operating room technology, pretreatment with antibiotics, and a constant awareness on the part of the surgical team. The inherent risk of infection associated with implantation of foreign material in the human body is exaggerated in orthopedic surgery by several factors. A major factor is the dead space always present around the wound after implantation of an orthopedic device. ² The formation of a hematoma in this dead space increases the risk of infection through several mechanisms. First, a hematoma is an excellent location for bacterial growth. Previous studies have suggested that antibiotics administered postoperatively do not penetrate hematomas easily and may not reach a clinically effective concentration in the hematoma. ³ Second, presence of the hematoma can also devascularize the surrounding tissue, thus decreasing the ability of normal defense mechanisms to enter the affected area. The presence of a hematoma can also prevent the entry of antibiotics into the tissue near the wound. ²

Another factor contributing to the risk of infection is the inherently low blood flow to cortical bone. ⁴ This is compromised to a greater extent by the surgical techniques required for device implantation. Reaming of the bone causes death of the tissue in the immediate area, further decreasing blood supply. Ultimately, this results in an increased presence of devascularized and dead bony tissue. This condition may last for at least 1 year after surgery. ²

In addition to the inherent risks of infection associated with arthroplasty, patients with conditions such as increased age, obesity, use of corticosteroids, diabetes mellitus, and rheumatoid arthritis are further at risk. Malnutrition also places individuals at a greater risk of infection. ^2,5 These factors should be considered by the surgeon when considering surgery and planning postoperative care for the patient.

The term osteomyelitis is defined as inflammation in bone. Most frequently, this condition is secondary to the presence of a bacterial infection. In the orthopedic literature, osteomyelitis is often used to indicate infection in bone not necessarily associated with the presence of an implanted device. In this study, the terms infection and bone infection will be used rather than osteomyelitis. Unless otherwise indicated, this is in reference to infections in bone associated with an implanted orthopedic device.

Historical Considerations

Infections in the bone have been insidious since the beginning of recorded time. ⁶ Hippocrates is credited with accurately describing bony infections and recognizing the relationship between nonhealing wounds and the presence of dead bone. ⁶

The ability to prevent infection in bony injuries did not advance substantially for many years. In the late 1800s, techniques for cleaning wounds were developed. This included the use of Dakin’s solution and the use of maggots to debride dead tissue. The latter approach was used as late as 1928; however, the method fell into disuse because no advantage over surgical technique was found. ²

The introduction of sulfonamides in the 1930s signaled the advent of the antibiotic era. When combined with improved surgical techniques, the use of sulfonamides represented a major step forward in the prevention and treatment of bone infection. ² The next major step forward in the treatment of bone infection coincided with the introduction of penicillin after World War II. Since then, the development of more affective antibiotics and improved drug delivery techniques has increased our ability to treat infection in the bone; however, prevention still remains the most effective weapon. In an otherwise healthy individual, mortality from infection of bone is low in the United States; however, the presence of an orthopedic implant substantially increases the risk of death. ³ Any patient who develops an infection in the bone secondary to implantation of an orthopedic device will face increased morbidity and the likelihood of a delayed recovery and prolonged disability. ^2,6

John Charnley, an orthopaedic surgeon in England, is credited with making hip replacement a successful operation. He stated: “Postoperative infection after total hip replacement is the saddest of all complications; it is sad because it seriously limits the success of any subsequent operation undertaken to revise a poor result following a first intervention.”⁷ Charnley’s battle with postoperative infection is an interesting historical illustration of the challenges faced by joint implant surgeons. Charnley had success anchoring the prosthetic components in the bone of the hip by using dental cement in 1957. His early total hips all failed, however, due to premature wear of the acetabular components that were made from Teflon, a material chosen for its property of low friction; however, it turned out to be too soft. After changing the acetabular cup to high-density polyethylene, Charnley’s first successful total hips were implanted in 1960, in a conventional operating room. However, his success was limited by a 7% rate of infection. Charnley tried to reduce the bacteria in the operating room environment by building an enclosure that isolated the patient’s surgical site from the anesthesiologist, OR nurse, and any visitors in the room. Only the surgeon and his assistant were within the enclosure, nicknamed the “greenhouse.” Even the patient’s head, arms, and shoulders were outside the enclosure. ⁸ The enclosure alone, used from late 1961 to mid 1962, reduced the infection rate to 3.5%. ⁹ Charnley’s next refinement, implemented from mid 1962 through 1966, increased the number of air exchanges per hour in the OR from 10 to 130, and dropped the rate of infection to 3%. ⁹ Charnley then designed and installed a system that created directional (laminar) air flow carrying airborne bacteria away from the surgical site and allowing 300 air exchanges per hour. This laminar flow system used within the greenhouse enclosure lowered the infection rate after 865 total hip replacements from mid 1966 to late 1967 to 1.5%. ⁹ Charnley’s next step toward reducing bacteria in the operating environment was to augment the surgeon’s gown, which is exposed to the patient, with an extra layer of material. This front apron, used from late 1967 to late 1969 further lowered the postoperative infection rate to 1.07%. ⁹

Although his innovations over a 9 year period had reduced the rate of infection from 7 to 1%, Charnley was not satisfied. He subsequently developed a “body exhaust” system for the surgeon and assistants. Use of this system for 5,405 hip replacements from January 1970 through December 1974 resulted in a rate of postoperative infection of 0.61%. ⁹ This low infection rate was achieved without the adjunctive use of systemic prophylactic antibiotics. Charnley made the decision not to use prophylactic antibiotics deliberately, for fear of producing infections caused by resistant organisms and so that his other measures to prevent infection could be studied with scientific validity. ^8,9 Armed with newer information regarding the efficacy of systemic antibiotics, however, in an address to hip surgeons in 1982, Charnley stated “Because of the tragic seriousness of postoperative infection, I am prepared to combine a perfect ultra clean air operating room environment with antibiotic prophylaxis. I hope this demonstrates how very seriously I regard it as our duty to continue in the future to study to eliminate postoperative infection by any means, or combination of means, whatsoever.”⁷ Charnley’s practice of using laminar air flow and body exhaust suits in the operating room is still used by joint implant surgeons today.

Frequency of Total Joint Replacement Procedures in the United States

An average of 531,000 arthroplasties were performed annually between 1985 and 1988 in the United States. In 1985, the most frequent arthroplasty procedure was performed on the hip. ¹⁰ In only a few years, the number of the type of arthroplasty procedures changed substantially in the United States. From 1993 to 1995, an average of 648,000 arthroplasties were completed each year in the United States. Of these, 47% were total knees and 38.5% were total hips. The number of total knee replacements increased 67% in just 5 years, from 125,000 in 1990 to 216,000 in 1995. ⁸ It is estimated that, by the year 2030, the number of total knee replacements will reach 454,000. This increase is due to both an increase in patient population and the effect of population aging. During the same time frame, it is estimated that the number of total hip replacements will increase to 106,000. ¹¹ This represents an increase of approximately 80% and 75%, respectively, during a 30 year period.

Will the rate, number, or both, of bone infection cases acquired secondary to arthroplasty increase in the future? Several factors should be considered before this question is answered. A significant portion of the estimated increase in arthroplasty procedures is attributed to an increase in the age of our population. Potentially, this could increase the incidence of infection in bone due to several factors. First, increasing age is accepted as a risk factor for infection due to decreased immune system function and an increase in malnutrition frequently seen in the elderly. Second, increased longevity will undoubtedly increase the number of hip revisions, a more extensive procedure also associated with an increased risk of infection. New antibiotics will be developed, which will be useful in the prevention and treatment of infection; however, an increase in drug resistant bacteria will have the opposite effect. The balance of these two factors is difficult, if not impossible, to estimate at this time. This knowledge is important in predicting the future cost to society produced by bone infections. Assuming no change in the rate of infection, the total number of cases can be expected to rise substantially due solely to the anticipated rise in the number of procedures that will be performed in the future. This alone will inflict a substantial financial burden on the medical system.

Prevention of Infection During Joint Replacement

Several uncontrollable factors predispose patients undergoing arthroplasty to an increased risk of infection. It is well accepted that the introduction of a foreign body decreases the number of bacteria required to produce a clinical infection. Elek and Conen ¹² demonstrated this in a controlled study conducted more than 40 years ago. In their study, a subcutaneous injection of 10⁶Staphylococcus aureus organisms did not produce an infection if no foreign body was present. In a similar setting, compromised by the presence of a foreign body, infection was produced by as few as 100 organisms. ¹² When combined with additional factors associated with patient health, the length of the operation, and low circulation in the bone, the risk of infection is always present. Because of these concerns, strict adherence to aseptic techniques during each case is essential if the number of infections is to be controlled.

As in any surgery, preparation of the patient before the operation is very important. Any number of disinfectant agents can be used to remove bacteria from the patient’s skin. ² It is impossible to remove all bacteria from the hair follicles; however, the number can be reduced substantially by the use of well accepted patient preparation techniques. It is now recommended that the skin be shaved only over the surgical incision site and this should be accomplished at the time of surgery. Shaving the night before can produce a local microenvironment suitable for bacteria growth, thereby increasing the risk of patient infection. ² Appropriate preparation and draping of the patient is mandatory but does not guarantee the prevention of infection.

The use of prophylactic antibiotics is the most effective means of reducing the prevalence of postoperative wound infection after joint replacement surgery. ¹³ Although the timing, agent, and duration of administration of prophylactic antibiotics are controversial, many surgeons chose to administer 1 g of cefazolin 30 minutes before the skin incision. This first generation cephalosporin is chosen because it has a long serum half-life, is relatively nontoxic, and is inexpensive compared with other antimicrobial agents. ¹³ For patients with a true Type I hypersensitivity to penicillin, vancomycin is an excellent alternative for prophylaxis, ¹³ although it is relatively more expensive, toxic, prone to development of resistant bacteria, and cumbersome to administer perioperatively. There is no evidence to support administration of prophylactic antibiotics beyond 24 hours after surgery, although some surgeons choose to continue prophylaxis until all indwelling catheters (urinary, wound drainage) are removed.

Addition of antibiotics to the irrigation used during surgery is also controversial. Topical antibiotic irrigation fluids have not been studied extensively in the clinical setting of total joint arthroplasty. Support for the use of topical antibiotic irrigation is present in the general surgical literature; thus, use during implantation of orthopedic devices seems reasonable. ¹³

The addition of antibiotics to acrylic bone cement to reduce the rate of infection after joint replacement has been studied in the orthopedic literature. There are studies that show a statistically significant reduction in infection after primary joint replacement surgery with the addition of antibiotics to the cement. Most notably, the Norwegian arthroplasty register of 10,611 primary hip arthroplasties revealed a 0.4% rate of revision for infection when both antibiotic-impregnated cement and systemic prophylactic antibiotics were used. The relative risk for infection without antibiotic cement was 4.3. ¹⁴ Similarly, in a study of revision procedures and those in which a metallic implant had been previously implanted, gentamicin-impregnated cement reduced the rate of infection significantly (2.83 to 0.52%, and 4 to 1.82%, respectively). ¹⁵ Addition of small amounts of heat stable powdered antibiotics does not significantly weaken the cement and, therefore, does not shorten the useful life of the implant. ¹⁶ At this time, most joint implant surgeons choose to add antibiotics to cement for selected revision procedures but not for all primary procedures. This strategy will probably continue until the long-term efficacy and cost benefits are better studied. ¹³

Other than hematogenous infection, infection after joint replacement is directly related to environmental contamination. ¹⁷ Lidwell showed a direct correlation between infection rates after joint replacement and environmental OR contamination. ^18,19 Most bacterial contamination gets transferred to the wound secondarily after first landing on supposedly “sterile surfaces.”²⁰ Ritter ¹⁷ in Mooresville, Indiana, has studied the operating room environment extensively. The following summarizes his findings. Operating room personnel are the major source of bacteria in the OR. ¹⁷Staphylococcus aureus has been cultured from one third of all OR personnel and S. epidermidis is cultured almost every time from OR personnel. ²¹ The quantity of environmental bacteria is related directly to the amount of bacteria OR personnel shed and the number of people present. ²² Facemasks and head covers offer no environmental protection. The use of body exhaust is helpful, however all OR personnel, including anesthesia, nurses, and visitors, must wear inclusive gowns. This is often not practicable.

Laminar air flow is most helpful with greater than 90% reduction of airborne bacteria at the wound and 60% reduction of airborne bacteria in the OR. ¹⁷ Ritter advises, “…to reduce environmental bacterial contamination the number of personnel in the operating room and the length of time for the actual surgery should be reduced, because wound contamination occurs first by direct fall out from environment and second by contaminated equipment and gloved hands that initially were contaminated by the environment.”¹⁷

Diabetes mellitus, obesity, extreme age, and malnutrition compromise immune status and are important factors in the host’s ability to control bacteria that inevitably settle into the wound during surgery. Rheumatoid arthritis doubles the risk of infection for both hip and knee replacement. Local factors such as prior surgery can adversely affect the outcome because of the decreased vascularity of scar tissue and the increased time required to perform revision surgery. ²³

Infection after joint replacement can be iatrogenic, due to direct contamination of the surgical wound, or hematogenous, due to seeding of the operative site at any time after the completion of surgery. The prevalence of hematogenous infection is unknown. It can occur in the early postoperative period or years later. The Mayo Clinic group has shown a time dependent wound susceptibility predisposing hematogenous infection, based on incidence rates for infection after joint implantation. The incidence of infection caused by different organisms decreases sharply for the first 3 months after surgery and continues to decrease until 2 years postoperative, at which point it levels off. ¹³ These data suggest that additional measures to minimize the risk of hematogenous seeding of artificial joints may be warranted for the first 2 years after implantation. Elective procedures that may cause bacteremia, such as teeth cleaning and other dental procedures, genitourinary or gastrointestinal procedures should be delayed or avoided, during this period, if possible. Due to these concerns, consideration should be given to administering prophylactic antibiotics to patients with artificial joints that must undergo invasive procedures. An advisory statement prepared by an expert panel of infectious disease specialists, the American Dental Association, and American Academy of Orthopaedic Surgeons was released in 1997. ²⁴ Antibiotic prophylaxis is recommended for any high-risk patient who is undergoing a high-risk dental procedure, such as cleaning, extraction, or root canal. The prophylactic antibiotics, penicillin or clindamycin, are specific for oral flora and should be taken 1 hour before the procedure. High risk patients include those less than 2 years out from surgery, and those with rheumatoid arthritis, lupus, diabetes, prior prosthetic joint infection, malnourishment, or hemophilia.

Development of Infection in Bone after Implantation of an Orthopedic Device

Bone infection can be caused by either gram-positive or gram-negative bacteria, with gram-positive bacteria being the most common culprit. When all cases are considered, S. aureus is the leading cause of bone infection; however, S. epidermidis causes more infections in patients when orthopedic devices are present. ^25,26 Bacterial adherence to biomaterial is a crucial event in the pathogenesis of prosthetic joint infection. Adherence is a complex multistep process that is influenced by bacterial, biomaterial, and host-derived factors. S. epidermidis possesses a number of polysaccharide and proteinaceous adhesions to enable S. epidermidis to quickly and avidly adhere to biomaterials. ²⁵

In the operating room, the patient’s own skin is the primary source of staphylococcal surgical bacteria. During the operation, S. epidermidis can enters the host body through the surgical incision. ²⁵ The presence of the prosthetic device causes chronic inflammation, thus impairing the body’s ability to phagocytize the bacteria. This impaired phagocytosis inhibits the body’s ability to destroy the bacteria, thus allowing even small numbers of the organism to establish a colony on the device. ^27,28

Infection in bone can also be induced by bacteria spread through hematogenous routes. S. aureus is the most predominant pathogen spread via this mechanism. Once again, the presence of the prosthesis is paramount to the establishment of the bacterial infection. Without the presence of the foreign body, significantly greater numbers of bacteria are required to produce adverse affects.

In a much smaller number of patients, bone infection is produced by gram-negative organisms. Bacteria referred to as enterics are the gram-negative organisms most frequently causing infection in bone. The members of this group (i.e., the Enterobacteriaceae family) most frequently associated with infection include Escherichia, Klebsiella, Proteus, and Enterobacter. ²⁹ Infections occurring shortly after implant of a joint prosthesis are generally caused by gram-positive cocci. Infection in bone produced by gram-negative bacteria usually appears later. The delayed appearance of gram-negative infections would suggest that these infections are caused by organisms from exogenous sources such as pulmonary infections, gastrointestinal infections, genitourinary tract infections, and wound infections near the implant. Dental manipulations have also been implicated in the development of these delayed cases of bone infection. ²⁴

Frequently, more than one type of bacteria is involved in the infection process. ²⁹ These multibacterial infections account for more than two thirds of adult bone infection cases. Frequently, S. epidermidis is present and accompanied by one or more different bacteria strains.

Diagnosis of Bone Infection

One third of bone infections occur within the first 12 weeks after implantation of an orthopedic device. ²³ These patients present with an elevated temperature and a joint that is tender and warm. The incision may drain spontaneously. Identification of the exact location of the infection is important, but it is often difficult to determine whether the infection is located in the superficial portions of the wound or extends into the joint. The erythrocyte sedimentation rate, C-reactive protein, or both, may be elevated, but this finding does not help separate superficial from deep infection. Roentgenograms are usually normal.

Technetium bone scans will usually be positive and are of little value in separating superficial from deep infections. Gallium-67 and indium-111 scans produce similar results. ⁶ Definitive determination of the infection location may require reoperation. If reoperation is undertaken and the infection is suspected of being superficial only, care should be taken to prevent transmission of bacteria into the joint. The surgeon should follow the primary incision route down to the deep fascia. The suture should be carefully examined to determine whether the infection extends below the superficial layers. If the physician cannot make a positive determination based on these observations, a needle aspiration of the joint should be used to make the definitive diagnosis. If the infection is found to be superficial only, the wound should be irrigated with large volumes of physiologic solution containing antibiotics. All necrotic tissue should be removed, and the area closed loosely leaving a suction drain in place. ⁶ Appropriate antibiotics and appropriate wound care should be initiated to control the infection and prevent its spread. The area should be monitored closely to determine whether spread into the joint occurs.

Infection in a patient with an artificial joint is classified based on the time elapsed from the initial surgery, until they present with infection. Acute infections are present within 12 weeks, subacute within 12 to 52 weeks, and late after 1 year. ²³ An infection at the site of an arthroplasty should be treated aggressively. Delay in either diagnosis or initiation of appropriate treatment may adversely affect outcome. Salvage of the artificial joint may be possible if the infection is detected early, the components are well fixed in the bone, and the organism is sensitive to antibiotics.

Treatment of Infection Associated with Orthopedic Devices

As mentioned previously, the presence of a foreign body significantly decreases the number of bacteria needed for colonization. This is certainly true with orthopedic implants such as total knees and total hips. Bacteria appear to attach to the prosthetic surfaces and form protective barriers or bacterial biofilms over the colony surface. Once developed, the biofilm helps the bacteria adhere to the prosthetic device, colonize, and increase their resistance to antibiotics. ^26–29 The growth rate of different bacteria known to produce varying quantities of slime biofilm was measured across time. In this study, it was shown that the high slime-producing bacteria showed more adherence than those producing low amounts. The slime producing bacteria also grew more rapidly. ^27,28 These indicate that biofilm production by bacteria is an important component in both the adherence and growth of bacteria on artificial surfaces. Because of this, the standard treatment for infections after implantation of orthopedic devices initially involves removal of the device. This procedure is followed by debridement of bone and affected soft tissue followed by the administration of appropriate antibiotics. ^2,6

Treatment of infection associated with an artificial joint is based on several factors. The patient’s overall health and ability to fight infection and withstand further operative interventions is important. The causative organism(s) and its sensitivity to antibiotic treatment are relevant. The time elapsed since the onset of infection is also important. There are four general approaches that can be taken: retention of components, two stage revision, one stage revision, and resection arthroplasty.

First, if the infection is detected early, within 3 to 6 weeks of onset, and the infecting organism is of low virulence and susceptible to antibiotic treatment, and the artificial joint is well affixed to bone, retention of the artificial joint may be possible. ³⁰ This approach may also be taken in a sick patient who is unable to withstand surgical intervention. In the former case, the chance for success is reasonable, after appropriate surgical debridement and administration of antibiotics, intravenous for at least 6 weeks and subsequently orally. In the latter case, chronic antibiotic suppression is warranted. Despite this, success is limited for patients with late chronic infections.

The second approach to a patient with an infected artificial joint, two stage revision, is the standard. ³¹ This approach involves removal of the prosthesis, including any foreign material such as bone cement and plastic plugs used to restrict the flow of cement down the femoral canal. More than one debridement may be necessary, until the patient is clinically free of infection. The prosthesis is left out for a period of at least 6 weeks while the patient receives intravenous antibiotics under the direction of an infectious disease specialist. A cement spacer that contains high concentrations of antibiotics is often implanted. This serves two functions. First, delivery of high concentrations of antibiotics to the site of the infection maximizes local bacterial eradication while minimizing toxic side effects. Second, the spacer facilitates subsequent re-implantation by maintaining the tissues around the joint in a physiologic tension. If, and when, based on clinical judgment and laboratory tests, the patient is free of infection, a new artificial joint can then be reimplanted. Antibiotic impregnated cement is often used at reimplantation. Using this approach, success in eradicating infection can be achieved in approximately 90% of patients.

The third method of treatment is the one stage revision. ³¹ Several centers have reported 80 to 90% success in treating prosthetic infections with one stage revisions. With this approach, the infected prosthesis is removed and the joint thoroughly debrided, and a new joint implanted at the same surgery. This approach is attractive for patients that may have difficulty tolerating more than one operation and the period of time without a joint, during which mobility is limited.

The fourth approach to a patient with an infected artificial joint is to remove the artificial joint and leave it out permanently, so-called resection arthroplasty. This approach results in decreased function and should be reserved for those patients with immune compromise, inadequate bone stock, loss of important hip stabilizing muscles, or persistent infection despite repeated debridement. ³⁰

The oral administration of antibiotics alone is inappropriate for the treatment of patients with infected bone. Orally administered antibiotics never reach adequate concentration in the infected bone. Parenteral administration of antibiotics for 6 weeks has become a standard antibiotic therapy for systemic administration. Although this time frame has not been scientifically proven, studies have suggested that it takes 4–6 weeks for debrided bone to be protected by revascularized tissue. ²

Summary

Infections secondary to the implantation of orthopedic devices occur in 1 to 3% of all arthroplasty procedures. This rate is influenced by the patient’s condition (age, nutritional status, immunologic status, etc.) and by the type of surgical procedure. Primary cases have a lower incidence of infection than secondary procedures. Strict adherence to aseptic conditions is essential in reducing the risk of bacterial infection. The use of preoperative antibiotics and ultra clean rooms has also been shown effective in further reducing the risk of infection after implantation of an orthopedic device. The most frequent organism producing infection after arthroplasty is S. epidermidis. Multibacterial colonies are present in up to two thirds of all cases. Gram-negative bacteria are less frequent producers of infection in bone; however, they may be present either by themselves or in combination with other bacteria. It can be difficult to separate infections in the superficial layers of the tissue from those that penetrate into the joint and bone. Reoperation and needle aspiration may be required to achieve a definitive diagnosis. The treatment of bone infection associated with an arthroplasty most typically involves removal of the orthopedic hardware. This removes a major site for bacterial colonization and increases the likelihood of a positive outcome. Necrotic bone and soft tissue must be debrided surgically prior to the administration of appropriate antibiotics. Systemic antibiotics are given intravenously for a period usually ranging up to 6 weeks; however, this time frame has not been proven scientifically. The local administration of antibiotics can be accomplished using an infusion withdrawal approach or by placement of cement that has been impregnated with antibiotics. This latter approach allows the physician to increase the concentration of the antibiotic in the local area without producing high circulating concentrations. Reimplantation of an orthopedic prosthesis should be considered only after the infected area has reestablished newly vascularized tissue and the infection is totally controlled. The influence of infection in bone on the practice of orthopedic surgery and our medical community in the future is uncertain. The positive effects of new antibiotics will be countered by the presence of new strains of bacteria that are antibiotic resistant. If the percentage of arthroplasty cases that develop infection remains constant, the total number of cases can be expected to increase by 75% in the next 30 years, because of the predicted increase in total joint procedures.