Most joint replacement surgery is performed for elderly patients. (See also Chapter 17) In a few percent of cases their postoperative course is complicated by infection, and the outcome is poorer with higher mortality and morbidity than in younger patients (25,26). Patients with rheumatoid arthritis have both a higher incidence of joint infection following surgery, and have a poorer outcome when infection occurs. Other groups of patients said to be at greater risk include those with previous surgery on that joint, diabetes mellitus, poor nutritional status, and very old patients. In general, the range of infecting organisms is much broader in the latter susceptible patients, and the fluid should be cultured for less common pathogens such as anaerobic bacteria, fungi, and mycobacteria.
A classic acute presentation of prosthetic joint infection with fever, pain, and inflammation, suggests infection with S. aureus, streptococci, or enteric bacilli. On the other hand, many months or even years after surgery less virulent organisms, such as coagu-lase-negative staphylococci, viridans streptococci, or diphtheroids, or rarely anaerobic bacteria, may be cultured during an evaluation for chronic joint pain or for radiographi-cally noted loosening of the prosthesis. When joint infection follows wound infection, multiple pathogens may be present. Some advocate preoperative treatment of asymptomatic bacteriuria, with the hope of reducing infection risk (25). Radiography, including various types of scans, is of uncertain usefulness—the gold standard for diagnostic testing remains joint aspiration and examination of synovial fluid. In contrast to routine aspiration of nonprosthetic joints, the presence of a foreign body in a joint means that accidental inoculation of organisms during needle aspiration is a special hazard.
The best hope of cure requires a two-stage surgical procedure—removal of the prosthesis and cement is accompanied by a 6-wk course of bactericidal antibiotic therapy chosen on the basis of in vitro susceptibility studies (26). Reimplantation is performed at the conclusion of the 6-wk antibiotic course. A new prosthesis may not be feasible at all, however, and the realistic options for some elderly patients may be limited to joint fusion or amputation. Simple surgical drainage with retention of the prosthesis plus a defined course of antibiotic therapy is generally not successful, and should be reserved only for acute cases (symptoms no longer than 5 d) that are promptly diagnosed, drained, and treated vigorously (27)—even then, success with this approach is achieved in only about a third of patients (25). Antibiotic therapy should be continued longer than 6 wk if the prosthesis is left in place (28,29). There are no studies of suppressive or follow-up oral therapy, although the availability of excellent new oral antibiotics makes this a reasonable choice for some patients.
Patients with rheumatoid arthritis have the highest incidence of septic arthritis, most often due to S. aureus. As many as half of elderly patients with septic arthritis have underlying rheumatoid arthritis, and about 20% of patients with rheumatoid arthritis develop joint infections at some time during the illness (22). Polyarticular infection that can resemble an excerbation of their underlying disease is peculiar to patients with rheumatoid arthritis. Their predispositions to infection include chronically inflamed joints, corticosteroid and other antiinflammatory therapy, breakdown of rheumatoid nodules, and ulcers in the skin overlying deformed joints. Symptoms of infection tend to be insidious and the diagnosis of infection is delayed or ascribed to the underlying disease; perhaps as a result, outcomes tend to be worse than septic arthritis in patients without rheumatoid arthritis (22). In most circumstances, an acutely inflamed joint in a patient with rheumatoid arthritis should be considered to be septic arthritis until infection has been excluded.
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