| Diagnosis of orthopaedic prosthesis infections with radionuclide techniques; clinical application of various imaging methods | ||
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Coventry (1975), and later Fitzgerald et al. (1977), described perhaps the most common system for the classification of infections in total hip arthroplasty. This classification is based on the mode or timing of infection.
Type I infections originate at the time of operation and become symptomatic in the immediate postoperative period. They are called early postoperative infections. The patient is usually seen during the first month after the operation, and the diagnosis can be made on the basis of a medical history and a physical examination. Systemic signs of infection may be present, and there is usually continuous pain. The wound may be erythematous, swollen, fluctuant and tender and there may be purulent wound drainage on examination. These infections are caused by infected hematomas and wound infections spreading to the periprosthetic space.
Type II infections are also believed to originate at the time of operation, but the onset of symptoms in these cases is delayed. These infections are also called late chronic infections. The patient is usually seen between six months and two years after the operation. This type of infection is associated with deteriorating function and increasing pain. Pain is often present from the time of the procedure, and it may be activity-related or occur during rest. Early loosening of the components is often the only clue to infection, and systemic symptoms are not part of the presentation. The findings on examination are non-specific and similar to those associated with aseptic loosening.
Type III infections, also called hematogenous infections, are the least common and are caused by hematogenous spread to the hip, which usually occurs two years after arthroplasty or later. Dental manipulation, catheter-associated urinary tract infections and remote infections may trigger hematogenous seeding. Streptococci are more frequently isolated in this type of infections than in others. There is generally a febrile episode accompanied by sudden deterioration of the hip. These infections are likely to occur in patients who are immunosuppressed for inflammatory arthropathy or transplantation and in patients with recurrent episodes of bacteremia (Spangehl et al. 1998).