Patient-Dependent Factors

Surgeon-Dependent Factors

Laboratory Studies

A complete blood cell count, including differential and erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), should be obtained during initial evaluation of bone and joint infections. The white blood cell count is an unreliable indicator of infection and often is normal even when infection is present. The differential shows increases in neutrophils during acute infections. The ESR becomes elevated when infection is present, but this does not occur exclusively in the presence of infection. Fractures or other underlying diseases can cause elevation of the ESR. The ESR also is unreliable in neonates, patients with sickle cell disease, patients taking corticosteroids, and patients whose symptoms have been present for less than 48 hours. Peak elevation of the ESR occurs at 3 to 5 days after infection and returns to normal approximately 3 weeks after treatment is begun. CRP, synthesized by the liver in response to infection, is a better way to follow the response of infection to treatment. CRP increases within 6 hours of infection, reaches a peak elevation 2 days after infection, and returns to normal within 1 week after adequate treatment has begun. Other tests, such as the S. aureus surface antigen or antibody test and counterimmunofluorescence studies of the urine, are promising, but their usefulness in clinical situations has not been proved. Material obtained from aspiration of joint fluid can be sent to the laboratory for a cell count and differential to distinguish acute septic arthritis from other causes of arthritis. In septic arthritis, the cell count usually is greater than 80,000/mm³, with more than 75% of the cells being neutrophils (Table 20-3). Jung et al. devised an algorithm to predict the probability of septic arthritis in children (Table 20-4). A Gram stain also should be obtained. Gram stains identify the types of organisms (gram-positive or gram-negative) in about a third of bone and joint aspirates. Intraoperative frozen section also should be obtained in cases in which infection is suspected. A white blood cell count greater than 10 per high-power field is considered indicative of infection, whereas a count less than 5 per high-power field all but excludes infection.

TABLE 20-3 Synovial Fluid Analysis

From Morrissy RT: Septic arthritis. In Gustilo RB, Genninger RP, Tsukayama DT, editors: Orthopaedic infection: diagnosis and treatment, Philadelphia, 1989, WB Saunders.

Imaging Studies

Radiographic studies are helpful but are not as useful in the diagnosis of acute bone and joint infections as they are in following responses to treatment. Plain radiographs show soft tissue swelling, joint space narrowing or widening, and bone destruction (Fig. 20-1). Bone destruction is not apparent on radiographs, however, until an infection has been present for 10 to 21 days. In addition, 30% to 50% of the bone matrix must be lost to show a lytic lesion on radiographs (Fig. 20-2). Wheat found that fewer than 5% of plain radiographs were initially abnormal in bone and joint infections, and fewer than 30% were abnormal at 1 week; however, 90% were abnormal at 3 to 4 weeks. If initial radiographs are normal in the evaluation of bone and joint infections, other imaging methods that show soft tissue swelling and loss of normal fat planes around the involved bone or joint should be used.

FIGURE 20-1 A, Radiographic evidence of acute bone and joint infection. B, Treatment with antibiotic cement spacer.

(Courtesy of Andrew Crenshaw.)

FIGURE 20-2 Anteroposterior (A) and lateral (B) radiographs showing bone destruction.

Conventional tomography can be useful in identifying a sequestrum or subchondral bony plate destruction, although it has largely been replaced with more conventional radiographic methods. Arthrography helps document proper aspiration of a suspected septic joint. Dye should be injected only after fluid is obtained from the joint because the bactericidal effect of iodinated contrast material can cause a false-negative culture result. CT can help determine the extent of medullary involvement. Pus within the medullary cavity replaces the marrow fat, causing an increased density on the CT scan. Adjacent soft tissue abscesses also are seen easily (Fig. 20-3). CT diagnosis of acute osteomyelitis is based on detection of intraosseous gas, osteolysis, soft tissue masses, abscesses, or foreign bodies. Additionally, increased vascularity after administration of a contrast agent also can aid in the diagnosis. Narrowing of the medullary cavity by granulation tissue and new bone is readily shown during the healing phase of osteomyelitis. CT identifies sequestra in chronic osteomyelitis (Fig. 20-4). It also is helpful in identifying alterations in areas poorly seen on plain films, such as the sternoclavicular joint, sacroiliac joint, and spine. Contrast material can be used to delineate abscesses in necrotic tissue that does not enhance from surrounding hyperemic tissue.

FIGURE 20-3 CT of pelvic abscess in a child.

FIGURE 20-4 A and B, CT scans showing sequestra.

(Courtesy of Todd Williams.)

Ultrasonography can also be used to localize an abscess cavity, detect joint effusion, or guide a physician in the proper placement of the needle when obtaining aspirate from a bone or joint.

Radionuclide scanning has become a useful imaging adjunct in the diagnosis of osteomyelitis. Although radiography and CT give a structural or anatomical picture, radionuclide scanning gives a more physiological picture. Bone scintigraphy does not detect the presence of infection but, instead, reflects inflammatory changes or the reaction of bone to the infection. Radionuclide scanning also is useful in patients with metallic implants in whom CT and MRI are of limited value because of contraindications and metallic-generated artifact, although metal subtracting software is improving imaging in these patients. The three most commonly used radioisotopes are technetium-99m (^99mTc) phosphate, gallium-67 (⁶⁷Ga) citrate, and indium-111 (¹¹¹In)–labeled leukocytes. The most common is ^99mTc phosphate, which can detect osteomyelitis within 48 hours after clinical onset of infection. The uptake of this compound is related primarily to osteoblastic activity, although regional blood flow also plays a role in skeletal uptake. After intravenous injection, the technetium is distributed rapidly throughout the extracellular compartment. Bone uptake is rapid, with more than 50% of the administered dose being delivered to bone within 1 hour. The remainder of the dye is excreted by the kidneys into the urine.

The standard technique of ^99mTc phosphate imaging is to perform a three-phase study. Although this does not increase the sensitivity of the test significantly, it does increase specificity from 74% to 94%. The three-phase bone scan consists of images taken in (1) the flow phase, (2) the immediate or equilibrium phase, and (3) the delayed phase. The flow-phase image is similar to a radionuclide angiogram in that it shows blood flow. The equilibrium or blood pool image shows relative vascular flow and distribution of the radioisotope into the extracellular space. The delayed-phase image generally is obtained 2 to 4 hours after injection when renal excretion has eliminated most of the isotope except that taken up by osteoblastic activity. This image shows osteoblastic activity and is positive in numerous disease states, including osteomyelitis, tumors, degenerative joint disease, trauma, and postsurgical changes. Usually a focus of osteomyelitis appears as an area of increased tracer uptake on delayed images. To have a “hot spot” on a bone scan, the vasculature to the involved bone must be intact. If blood flow to the involved area is decreased by subperiosteal pus, necrosis (i.e., sequestrum), joint effusion, vasospasm, or soft tissue swelling, a “cold” scan may result.

A major disadvantage of three-phase ^99mTc phosphate bone scintigraphy is that the increased uptake caused by osteomyelitis is difficult to distinguish from that caused by degenerative joint disease or posttraumatic or postsurgical changes. The relative activity in each of the three phases may be helpful in differentiating other causes of increased uptake. Cellulitis causes increased activity during the flow and equilibrium phases and a decreased or normal uptake in the delayed phase. Osteomyelitis causes increased uptake in all three phases (Fig. 20-5). Increased uptake in the delayed phase but not in the flow or equilibrium phase suggests degenerative joint disease (Table 20-5). ^99mTc phosphate bone scans are unreliable in neonates (<6 weeks old) and usually are negative in 60% of these patients with bone or joint infections.

FIGURE 20-5 Three-phase bone scan showing osteomyelitis.

(Courtesy of Michael Fleming.)

⁶⁷Ga citrate is the oldest tracer and has been used to localize inflammatory lesions as well as malignant tissue. The mechanism of gallium deposition is controversial; it seems to be related to increased endothelial permeability or diffusion by transportation as gallium-transferrin. The specificity of a ⁶⁷Ga citrate scan alone is poor (82%). ⁶⁷Ga citrate scanning can be useful in osteomyelitis when it is used in conjunction with ^99mTc phosphate scanning. In purely reactive bone formation (posttraumatic or postsurgical), the intensity on the ^99mTc phosphate scan is proportionally greater than that on the ⁶⁷Ga citrate scan. In areas of inflammation, however, gallium uptake either exceeds that of technetium in relative magnitude or displays a different spatial configuration of activity. A disadvantage of ⁶⁷Ga citrate imaging is its slow clearance after injection, which requires a delay in imaging ranging from 24 hours after injection for the appendicular skeleton to 72 hours for the axial skeleton. Specificity decreases in ⁶⁷Ga citrate scintigraphy when the lesion is located peripherally rather than centrally. With the combination of ⁶⁷Ga citrate and ^99mTc phosphate scans, sensitivity and specificity are 70% and up to 93%, respectively, for the detection of osteomyelitis.

¹¹¹In–labeled leukocytes have been suggested for differentiating between osteomyelitis and reactive bone formation. This scan is positive at earlier stages of osteomyelitis than ^99mTc phosphate scintigraphy. The leukocyte scanning technique involves in vitro radionuclide labeling and injection of autologous leukocytes, predominantly polymorphonuclear neutrophilic leukocytes, followed by imaging 24 to 48 hours later. Fifty milliliters of the patient’s venous blood is obtained, separated from the other blood elements in vitro, and labeled with ¹¹¹In. The labeled leukocytes are reinjected into the patient, and scans are obtained at 24 hours. A scan is positive if focal accumulation of activity exceeds adjacent normal bone activity. Scintigraphy with ¹¹¹In has been reported to be helpful in the diagnosis of acute osteomyelitis, but there is disagreement about its efficacy in chronic osteomyelitis because the latter is predominantly lymphocytic and may give a negative or “cold” scan. The ¹¹¹In scan also is unreliable for differentiating between aseptic and septic loosening of a painful arthroplasty. Teller et al. did not recommend the routine use of ^99mTc phosphate with ¹¹¹In-labeled scans for detecting aseptic or septic loosening of arthroplasty because of the high cost associated with these tests and the low specificity and sensitivity of 78% and 64%, respectively. Prandini et al., in a meta-analysis, found that ^99mTc-labeled white blood cells had a greater sensitivity (89%) and specificity (90.1%) than ¹¹¹In-labeled white blood cells. Several authors have recommended prolonging the scan time until 24 hours for the ^99mTc-labeled white blood cell scan to improve detection. ¹¹¹In-labeled monoclonal immunoglobulin is a substitute for ¹¹¹In-labeled leukocytes. It seems to be as effective as ¹¹¹In-labeled leukocytes, does not require phlebotomy, and avoids the risk of radiation to white blood cells and the perceived risk of malignant transformation. According to Hakki et al., compared with ¹¹¹In-labeled leukocytes and ^99mTc phosphate scintigraphy, monoclonal antibody fragment (LeukoScan, Granuloscint, NeutoSpect) has better sensitivity, specificity, and diagnostic accuracy. In addition, these researchers suggested that LeukoScan is a stronger diagnostic tool in patients with a low leukocyte count (i.e., human immunodeficiency virus [HIV]–infected patients) and in patients with chronic osteomyelitis. However, meta-analysis studies show that these agents are less accurate than in vitro–labeled white blood cells in most patients, and a risk of allergic reaction (some fatal) does exist especially when repeated scans are necessary. These agents have limited availability in the United States; however, the quest for a more perfect monoclonal antibody fragment continues. The detection of chronic osteomyelitis, especially of the central skeleton, can be enhanced with a ^99mTc/ciprofloxacin (infection) scan and fluorine-18 (¹⁸F)-fluorodeoxyglucose-labeled positron emission tomography (FDG-PET). FDG-PET is the most accurate test (92%) with the most positive predictive value (94%). It is extremely useful for chronic infections and infections already treated with antibiotics. However, it is the most expensive and is not readily available in all health care centers.

MRI has been used for evaluating bone and joint infections. MRI is a complex imaging method that aligns the body’s protons along the axis of a powerful external magnetic field and records the motion of the protons as they return to the magnetic field alignment after absorbing energy from a radiofrequency-generating coil. Each type of tissue has its own unique signal characteristics. Two parameters are evaluated. The first is the echo time (TE), which is the time that elapses between the initial radiofrequency pulse and its return back to the radio antenna (akin to a sonar ping). The second is repetition time (TR), which is the time between the applied consecutive radiofrequency pulses to the patient (the frequency of pings). When the TR and TE are short, a T1 image is produced that shows fat as a high, bright signal. When the TR and TE are long, a T2 image is obtained that shows water as a bright signal. An additional signal is obtained by suppressing the fat signal; this is called short tau inversion recovery (STIR). STIR signals have a high negative predictive value for osteomyelitis of almost 100%; however, STIR cannot be used to differentiate fluid collections (e.g., abscesses) from circumscribed soft tissue edema. The reported abnormal images reflect an increase in water content, resulting from edema in the marrow cavity. Marrow fat is replaced by edema and cellular infiltrates that are lower in signal than fat on T1 images and higher in signal than fat on T2 and STIR images. The classic findings of osteomyelitis on MRI are a decrease in the normally high marrow signal on T1 images and a normal or increased signal on T2 images (Fig. 20-6). According to Boutin et al., MRI is the most appropriate tool to rule out cartilaginous epiphyseal infection. Mazur et al. showed that MRI was superior in sensitivity (97%) and specificity (92%) to ^99mTc phosphate bone scintigraphy for detection of osteomyelitis. MRI detects changes (e.g., lytic areas) much earlier in the course of disease than radiographs because it shows the condition of the intramedullary cavity. The signal changes seen on MRI are nonspecific, and anything that causes edema or hyperemia (e.g., fractures, tumors, and inflammatory processes) produces signal changes similar to that of osteomyelitis. Although MRI is good for detailing marrow involvement and discitis, it does little to detect early cortical bone involvement.

FIGURE 20-6 MRI of abscess (images on left).

(Courtesy of Amber Turner.)

Gadolinium contrast material can be added to MRI to help distinguish an abscess (bright signal involved abscess with no enhancements of the fluid within the abscess) from coexisting cellulitis. In addition, it enhances granulation tissue surrounding a sinus tract or sequestrum but does not enhance the tract or sequestrum in the bone. Gadolinium contrast does not help in differentiating osteomyelitis from bone marrow edema.

In general, sequestra in sinus tracks, abscesses, and subperiosteal fluid collections are all positive MRI signs that suggest osteomyelitis. MRI should be reserved for patients with inconclusive findings, patients with infections involving the pelvis or spine, and patients who may require surgical intervention. It is extremely useful for detection of acute hematogenous osteomyelitis.

In summary:

Culture Studies

Although blood tests, radiographic imaging, and clinical signs all give presumptive evidence of an infection, they do not suffice for an actual bacteriological diagnosis that would allow development of a treatment plan including correct antibiotic selection. The laboratory has the responsibility of isolating and identifying the offending organism and determining antibiotic susceptibility. This process can be easier and more informative when there is proper communication between the orthopaedic surgeon and laboratory personnel. The latter should be informed of patient risk factors, antibiotic therapy, culture site, how the culture was obtained, and what possible organisms are sought.

The timing and selection of the culture are crucial. Most orthopaedic infections are deep seated, and adequate culture specimens are difficult to obtain. Despite this, every effort should be made to obtain a culture specimen before antibiotic therapy is begun. Cultures of superficial wounds or sinus tracks should not be relied on because they have been shown to be poor indicators of deep infection and usually are polymicrobial. Swab cultures of a sinus track give misleading results unless S. aureus coagulase is the predominant isolate or unless a single species is isolated in pure culture. The preferred specimen in most bacterial and yeast infections is aspirated fluid (joint or purulent fluid). A deep wound biopsy or a curetted specimen after cleaning the wound is acceptable. In certain bacterial and fungal infections, a tissue biopsy specimen from the edge of the wound is preferable. Aerobic and anaerobic swabs are more commonly used, but aspirated fluid or a tissue biopsy specimen is preferable. According to Levine and Evans, the use of blood culture vials intraoperatively for placement of aspirated fluid is more sensitive than swab cultures or tissue biopsy; however, others such as Wilson and Winn saw no advantage in using blood culture vials or swabs and that fluid sent to the laboratory in sterile environment was all that was required. Tissue specimens should be placed in small carbon dioxide–filled containers to reduce exposure to air.

Rapid diagnostic procedures that may aid in initial decision making are qualitative tests only. A Gram stain determines if gram-negative or gram-positive bacteria are present. Bacterial morphology and some measure of inflammation also can be obtained from a Gram stain. If the Gram stain is negative, and infection is strongly suspected because of the presence of many acute inflammatory cells, an acridine orange stain using a fluorescent microscope may aid in detection of gram-negative bacteria.

When a fungal infection is suspected, a 10% potassium hydroxide wet mount preparation or a fluorescein calcofluor white stain aids in the detection of characteristic fungal morphology. Other special stains, such as acid-fast, rhodamine auramine, or fluorescein-tagged antibody stains, also can help in making a rapid diagnosis. The development of monoclonal antibodies to specific bacterial antigens has had a major effect, but except for the detection of the bacterial antigens of H. influenzae, Neisseria meningitidis, and S. pneumoniae in synovial fluid these tests are useful only in the rapid identification of already isolated bacteria and not for detecting specific bacteria in a clinical specimen.

Several different types of media are available for isolation and identification of bacteria. The initial specimen should be cultured for aerobic and facultative and strict anaerobic organisms. Media for these organisms should include blood agar, chocolate agar for H. influenzae and Neisseria gonorrhoeae, and a nutrient-enriched broth for fastidious organisms. Selective media should be used when fungi or acid-fast bacteria are suspected. Usually an organism can be identified in 24 to 48 hours, but some isolates can take several days or weeks.

After the organism has been isolated and identified, its antimicrobial sensitivity should be determined. The three principal ways to test sensitivity or antimicrobial effectiveness are (1) in vitro susceptibility testing of a bacterial isolate, (2) measurement of the patient’s inhibiting or bactericidal serum level against his or her own infectious bacteria, and (3) measurement of actual serum concentration of the antibiotic the patient is receiving.

The National Committee for Clinical Laboratory Standards provides recommendations for standardized tests and suggests the prototype generic antibiotic that can be tested to represent each class of antibiotic when in vitro antimicrobial susceptibilities are performed. The in vitro susceptibility studies are based on (1) serial dilution of the test antibiotic in broth or on a solid agar medium, (2) antibiotic diffusion from a paper disc into a solid agar medium, or (3) antibiotic elution from paper disc into broth. The lowest concentration of an antibiotic that inhibits growth of the patient’s isolate is designated the minimal inhibitory concentration (MIC). If the MIC level can be easily achieved in the patient’s serum using normal dosage and route of administration, the organism is said to be susceptible or sensitive. After the MIC has been determined, a subculture can be performed to determine the minimal bactericidal concentration, which is the lowest concentration of antimicrobial agent that allows survival of less than 0.1% of the original cultured inoculum.

In the disc diffusion method, the zone of inhibited growth around an antibiotic-impregnated disc is measured and compared with a standard test bacterium. This is reported as sensitive, intermediate, or resistant, depending on the magnitude of the zone of inhibition. Broth disc elution is used for anaerobic bacteria. An antibiotic-impregnated paper disc is placed in an anaerobic broth and incubated along with the bacterium to be tested. Visual results are read as no growth (sensitive) or growth (resistant).

Measuring the serum bactericidal concentration (SBC) is another way of measuring antimicrobial effectiveness. The SBC measures the activity of the patient’s own serum against the infecting organism. The lowest dilution of the patient’s serum that kills 99.9% of a standard inoculum is called the SBC. This requires that the patient’s serum be obtained at peak and trough concentrations. This method has gained popularity in the treatment of pediatric septic arthritis and osteomyelitis to test the adequacy of oral antibiotic dosage. The oral dose is adjusted to give a peak SBC of 1 : 8 or 1 : 16 and a trough SBC of 1 : 2 or higher.

Actual antimicrobial concentration in serum also can be measured. This usually is done to determine whether an effective therapeutic level is being obtained and to guide antibiotic dosage to avoid toxic side effects.

Two special tests that can be used in orthopaedic infections are quantitative tissue cultures and in vitro antibiotic synergism versus antagonism susceptibility. Quantitative tissue culture has been helpful in detecting clinically significant infections in burn patients. Its use in orthopaedics has aided in decisions regarding wound closure and antibiotic therapy. After débridement of an open wound, a 1-mL tissue specimen is taken and a quantitative Gram stain smear is obtained from 0.01 mL of an undiluted homogenate. This is transferred onto a clean glass microscope slide and spread in an area not exceeding 15 mm in diameter. After drying, the slide is Gram stained and the entire smear is examined microscopically at a magnification of 1000. The presence of a single organism in any field indicates a positive smear, suggesting ongoing infection. The remainder of the tissue homogenate can be serially diluted in nutrient broth for quantitative culture. Cultures containing 10 organisms per gram of tissue have a high probability of remaining infected if closed. The accuracy of quantitative microbiological techniques has been reported to be 84% for Gram stain and 89% for culture. In vitro antibiotic testing for synergism and antagonism should be considered when a persistent infection is refractory to antibiotic treatment. This test measures the sum effect in vitro of two different antibiotics.

Often, antibiotic therapy is begun before a definitive culture result is obtained, and the selection of an antibiotic is based on the most probable causative bacteria, which varies considerably depending on age and epidemiological factors. S. aureus is most frequently isolated in infectious arthritis. After this, N. gonorrhoeae is more common in adults younger than 30 years, and H. influenzae type B is more common in children younger than 2 years. These three bacteria, along with various Streptococcus species, constitute most known isolates in joint infections. In contrast, prosthetic joint infections most often are caused by skin flora, such as S. epidermidis and other coagulase-negative Staphylococcus and gram-negative bacilli that are transient skin colonizers.

The etiological agent for osteomyelitis also depends on age, epidemiological factors, and whether the osteomyelitis is primary or secondary. S. aureus is the most frequent isolate in osteomyelitis, but Salmonella organisms have an increased incidence in patients with sickle cell anemia or neonatal osteomyelitis. Postsurgical osteomyelitis also has a predominance of skin flora and hospital flora. This is where an individual hospital statistical survey of infections would be beneficial.

Molecular diagnostic tests for detection of infections are still experimental, expensive, and not readily available. However, polymerase chain reaction techniques aimed at the bacterial 16 S rRNA DNA sequence can be performed. This identifies the presence of bacteria but not the specific organism. A high false-positive rate still exists, and improvements are still forthcoming with additional research and development. Moojen et al. have added a reverse line hybridization process that will identify some of the more common orthopaedic pathogens. The clinical usefulness of these molecular diagnostic tests is evident in several areas. They can identify the specific pathogens responsible for musculoskeletal infection even if pretest antibiotics have already been given, can identify organisms that cause low-grade infections (small concentration of organisms), and can rapidly recognize infections that usually have long culture times (e.g., tuberculosis).

Diagnostic Tests

Because the serological tests currently used for the detection of HIV depend on the formation of antibodies by the infected patient, there is a period of time known as the “window period” during which the patient is infectious before the appearance of the HIV antibodies. Most patients (approximately 99%) develop antibodies to HIV within 6 months of the initial infection, but delayed seroconversion (after 1 year) has been reported. Reliance on a single test may give a false sense of security.

The enzyme-linked immunosorbent assay (ELISA) was developed to test antibodies to the retrovirus. Because it is a serological test, the detection of HIV antibodies by ELISA indicates a past infection. The antibodies usually increase to levels detectable by this test in 1 to 3 months. If the test is reactive, it is repeated; if it remains reactive, a confirmatory test, usually a Western blot, is performed. According to the CDC, the sensitivity of the ELISA is at least 99% when it is performed under optimal laboratory conditions on serum specimens from individuals infected for 3 months or longer. The ELISA was designed to be overly sensitive and is more likely to produce false-positive than false-negative results. The most frequent reason for a false-negative result is that the infected individual had not yet developed antibodies to HIV at the time of testing.

Confirmatory Tests

The Western blot test is the most common confirmatory test. It is far less likely to produce false results, but they do occur. The probability of obtaining false-positive tests with the ELISA and Western blot testing sequence in a population with a low incidence of infection has been estimated to be 1 in approximately 350,000. Other confirmatory tests are the antigen detection test, in situ hybridization test, indirect immunofluorescence assay, radioimmunoprecipitation assay, and polymerase chain reaction test. The CD4 lymphocyte count is not a diagnostic test but rather a measurement of the degree of immunosuppression.

Musculoskeletal Syndromes in Human Immunodeficiency Virus–Infected Patients

The most common musculoskeletal syndromes in HIV-infected patients are manifestations of drug toxicity, reactive arthritis, infectious arthritis, myositis, tendinitis, and bursitis. General principles to be kept in mind when evaluating an HIV-infected patient with musculoskeletal problems include the following: (1) Any musculoskeletal syndrome that occurs in non–HIV-infected patients can occur in HIV-infected patients; (2) HIV infection can alter the clinical presentation, severity, and course of musculoskeletal problems; and (3) early diagnosis of infections is especially important to prevent their spread in an immunocompromised patient (Table 20-7).

TABLE 20-7 Musculoskeletal Syndromes in Human Immunodeficiency Virus–Infected Patients

From Lane N: HIV disease and arthritis: diagnostic and therapeutic dilemmas. In Cohen PT, Sande MA, Volberding PA, editors: The AIDS knowledge base, Boston, 1994, Little, Brown.

Reactive arthritis usually occurs in the foot and ankle. Tendinitis involving the Achilles tendon and the anterior and posterior tibial tendons is common. Septic arthritis occurs more commonly in intravenous drug abusers and hemophiliacs who have become infected with HIV. Gram-positive bacteria, such as S. aureus and S. pneumoniae, commonly found in noninfected patients with septic arthritis and bursitis, also are the most frequently reported organisms causing septic arthritis and bursitis in HIV-infected individuals. Primary osteomyelitis has been reported in HIV-infected patients, but usually it is the result of direct extension from a septic joint. An HIV-infected patient with a total joint prosthesis may be at an increased risk for infection as immunosuppression progresses.

Muscle pain or myositis is a common complaint in HIV-infected patients, including idiopathic polymyositis, polymyositis secondary to zidovudine toxicity, and pyomyositis. Idiopathic polymyositis and zidovudine polymyositis have similar signs and symptoms. Patients complain of muscle weakness and have elevated creatine phosphokinase levels, and muscle biopsy specimens show myofibril necrosis and associated inflammation. Pyomyositis, usually caused by S. aureus, can present as a solitary abscess or multiple abscesses within the muscle. The patient has fever, localized muscle pain, swelling, and erythema. Aspiration and systemic antibiotics usually are adequate treatment of pyomyositis, but surgical incision and drainage are occasionally necessary.

Risks and Prevention

The risk of orthopaedic surgeons contracting HIV infection from patients is unknown at this time. However, no documented seroconversion has ever been reported in orthopaedic surgeons. According to the CDC report through 2006, no new documented cases of HIV seroconversion have occurred in any health care worker since 2000. It is important for health care personnel to continue universal precautions to continue to keep the risk low. The potential for disease transmission still exist. Three factors that must be known to calculate an orthopaedic surgeon’s risk of incurring HIV from punctures in the operating room are (1) the frequency of punctures, (2) the percentage of surgical patients who are HIV positive, and (3) the risk of HIV transmission per needle stick from known HIV-positive patients.

At the end of 2008, it was estimated by the World Health Organization that approximately 33.4 million people worldwide were infected with HIV, and approximately 25 million had died of HIV-related diseases. Individuals with new infections in 2008 numbered 2.7 million with 430,000 being children younger than 15 years. At the end of 2008 women accounted for 50% of all adults worldwide with HIV infection. In the United States, it has been estimated that 0.4% of the population is HIV-positive with approximately 21% of positive patients unaware of their HIV infection. The exact prevalence of HIV-infected patients in a specific surgeon’s practice is impossible to calculate without prospective testing; however, it has been reported to be 10%, with regional and local variations in that trauma centers have a greater prevalence of HIV-infected patients. According to the CDC in 1986, the overall prevalence of HIV infection was 1% of the U.S. hospital population admitted for reasons other than HIV infection. The CDC reported in 1993 that only 30% of HIV-infected patients were recognized at the time of treatment. By 2006, 57 cases of documented occupational HIV infection in health care workers (nurses and medical technicians make up the vast majority) had been reported in the United States, and approximately 140 additional cases had a possible occupational etiology for HIV infection. Most (48) were related to a single percutaneous needle stick.

Lemaire and Masson noted that 6% to 50% of operations result in at least one blood contact between patient and health care worker, and 1.3% to 15.4% of procedures involve a sharp injury. Risk decreased with surgical experience but increased with operative time. Fitch et al. found that the greatest risk for occupational transmission of HIV involved parenteral injection of blood through orthopaedic pins or hollow-core needles. No cases of transmission from solid-core needles or exposure of an open wound to blood have been documented. Other potential sites of transmission include mucous membranes and isolated skin exposure. Risk increases with increased viral load of the patient, quantity of blood injected, and depth of inoculation. Based on data obtained by the American Board of Orthopaedic Surgeons, the estimated puncture rate for the orthopaedic attending physician is 2.8%, averaging approximately 10 punctures a year. In 1998, the CDC estimated that the percentage of HIV-positive patients averaged 1% to 5.6%, depending on the geographical area and the type of practice. The risk of transmission per needle stick has been estimated by the CDC to be approximately 0.3%. These figures put the annual risk to the orthopaedic surgeon between 0.025% and 0.5%, a cumulative (>40 years of practice) risk of 0.6%. The risk of transmission of HIV from an infected orthopaedic surgeon to a noninfected patient has not been reported.

In the absence of an effective means of prophylaxis, including a vaccine, the chief defense against HIV infection is the prevention of its transmission. Health care workers at risk are those most prone to sustain needle sticks, cuts, and skin tears in the presence of contaminated body fluids and tissues. The cases of HIV transmission through wounds underscore the importance of infection control procedures, especially in the operating room.

During orthopaedic surgical procedures, contact with blood and other body fluids containing blood in gross or microscopic amounts is frequent (3.7%). Lacerations from bone fragments and edges and cuts and needle sticks must be avoided. The estimated risk after a mucocutaneous exposure was reported to be 0.09% based on one seroconversion in six studies. The American Academy of Orthopaedic Surgeons (AAOS) has developed several basic recommendations for procedures in the operating room (Box 20-1). These precautions involve wearing surgical gowns that offer protection against contact with blood, using nontouch techniques for surgery and suturing, not passing sharp instruments from hand to hand (establishing a “hands-free” zone), and proper removal of contaminated gowns and postoperative scrub. Specific recommendations by the AAOS can be found in their information statement Preventing the Transmission of Bloodborne Pathogens (2008).

Chemoprophylaxis for occupational exposure to HIV is controversial. The most effective means of avoiding occupational HIV seroconversion is the employment of universal precautions. The practice of using protective eyewear is advised because projection of blood causes 3% to 5% of contaminations. Standard eyeglasses may provide protection because less than 5% of contamination has been found to be present on the protective side flaps of wraparound eye protectors. Double gloving reduces the risk of blood contact from 29% to 13%; however, the gloves must be changed at least every 2 hours or every hour for trauma cases. Indicator gloves also can be used to alert the surgeon to breaks in glove protection. Kevlar gloves should be used when bone fragments are present or saws are used.

After exposure of a health care worker to blood, a rapid HIV test should be performed on the source. If it is negative, no chemoprophylaxis should be offered. However, if it is positive, chemoprophylaxis should be offered. The rapid HIV test does have a low false-positive rate; therefore, all positive results should be followed with standard enzyme immunoassay and a Western blot assay. The test also will not identify HIV-positive patients if they have been infected less than 3 months. A decrease in seroconversion rates of 79% has been shown with the use of chemoprophylaxis after exposure using zidovudine and lamivudine, chain terminators for reverse transcriptase. Adding a protease inhibitor, indinavir, further decreases antiretroviral activity. These drugs should be started within 2 hours of exposure and generally are recommended for at least a 4-week course. In 2005, the CDC updated U.S. Public Health Service Guidelines for the management of occupational exposures to hepatitis B virus, hepatitis C virus, and HIV; recommendations for chemoprophylaxis can be found in Table 20-8. The most current postexposure prophylaxis (PEP) drug regimen can be found at the National HIV/AIDS Clinicians Consultation Center (http://www.ucsf.edu/hivcntr). Also questions about PEP can be answered at National Clinicians postexposure prophylaxis hot line (PEPline) at (888) HIV-4911. Most exposures to HIV-infected blood do not cause seroconversion, and toxicity of a chemoprophylactic regimen must be considered before the initiation of treatment. If available, consultation with infectious disease is recommended.

Additional concern for bloodborne pathogens extends to hepatitis. Approximately 10,000 health care workers become infected with the hepatitis B virus annually after an occupational exposure. The development of a vaccine for hepatitis B virus has resulted in a decrease of transmission and is recommended for most health care workers. The risk of hepatitis C has continued to increase. There is no PEP recommendation after contact with hepatitic C virus. Universal precautions should be used to decrease the risk of seroconversion from these pathogens.