Revision total knee arthroplasty: planning, controversies, and management--infection.
Routine blood work that includes ESR, CRP, and glucose levels, and plain radiographs and knee aspirations are obtained from our patients who have clinical suspicion of infection. If the culture result is positive and blood tests suggest infection, the surgical plan is a two-stage revision with an interval period of intravenous antibiotic administration. Risk factors are identified, and the patient's condition optimized. An infectious disease consultant is also involved in the treatment care plan and advises the patient about the best antibiotic, management of proper antibiotic levels, and home care. If culture results are negative, cultures are repeated every week for 3 to 4 weeks after the patient stops taking antibiotics. If the cultures yield positive results, a two-stage revision protocol is initiated. In patients who have 3 to 4 negative culture results, normal blood tests and radiographs, and no history of any immunocompromised state, such as diabetes or rheumatoid arthritis, diagnoses such as polyethylene wear or synovitis can be considered. If patients have any involved risk factor or blood tests, equivocal or suggestive, isotope scintigraphy is requested. We examine tissue in patients with positive scans and equivocal blood test results with clinical suspicion of infection. We prefer an open arthrotomy, which allows us to take multiple specimens for frozen section, assess fixation of the implant, and look for any other signs of infection. If the frozen section reveals more than 10 PMNLs per high-power field, we proceed to stage 1 revision after obtaining intraoperative cultures. If an organism grows in the cultures, stage 2 protocol is initiated. If no cultures are obtained at 7 to 10 days of incubation, we may consider earlier stage 2 revision at 4 to 6 weeks (Fig. 1). In patients in whom the frozen section reveals less than 5 PMNLs per high-power field, component fixation should be assessed, and if they are loose, revision of the knee should be initiated. As with a septic revision, use of antibiotic-impregnated cement can be considered for fixation. If the components are well fixed, a polyethylene tibial tray is exchanged. In either circumstance, intraoperative cultures should be obtained, and if they yield positive results, antibiotics should be continued for 6 to 12 weeks.