The AAOS gives a moderate strength of recommendation for synovial fluid testing including leukocyte count and neutrophil percentage, aerobic and anaerobic bacterial cultures, leukocyte esterase, alpha-defensin, CRP, and nucleic acid amplification testing (eg, polymerase chain reaction) for bacteria [54]. A recent manuscript advises intraoperative synovial fluid re-cultures are necessary even if the preoperative aspiration culture is positive and any discordance between preoperative aspiration culture and intraoperative synovial fluid culture should be noted [91]. If the joint aspirate culture is positive on the basis of both cell count with differential and positive cultures, then infection is considered likely and treatment is initiated [54,92]. In that setting, no further imaging is supported for the diagnostic workup of the infection. Berbari [46] studied 897 cases of periprosthetic joint infection and found that approximately 7% were associated with negative cultures. If the preoperative synovial cultures remain negative, multiple intraoperative periprosthetic tissues should be submitted for aerobic and anaerobic bacterial culture [54]. MRI Knee Without and With IV Contrast MRI may have a role in the workup of periprosthetic infection. Advances in metal artifact reduction may expand the potential role of MRI. Using metal reduction techniques, Potter and Foo found that infected synovium has hyperintense laminar appearance, distinct from the appearance of particle disease [22,93]. They noted that, in selected cases, MRI may be helpful in detecting extracapsular spread of infection and abscess formation. IV contrast may provide additional benefit in this regard [93]. On the basis of their findings, Plodkowski [94] examined 28 patients with proven infected TKAs and 28 controls with noninfected TKA.
Imaging After Total Knee Arthroplasty. The AAOS gives a moderate strength of recommendation for synovial fluid testing including leukocyte count and neutrophil percentage, aerobic and anaerobic bacterial cultures, leukocyte esterase, alpha-defensin, CRP, and nucleic acid amplification testing (eg, polymerase chain reaction) for bacteria [54]. A recent manuscript advises intraoperative synovial fluid re-cultures are necessary even if the preoperative aspiration culture is positive and any discordance between preoperative aspiration culture and intraoperative synovial fluid culture should be noted [91]. If the joint aspirate culture is positive on the basis of both cell count with differential and positive cultures, then infection is considered likely and treatment is initiated [54,92]. In that setting, no further imaging is supported for the diagnostic workup of the infection. Berbari [46] studied 897 cases of periprosthetic joint infection and found that approximately 7% were associated with negative cultures. If the preoperative synovial cultures remain negative, multiple intraoperative periprosthetic tissues should be submitted for aerobic and anaerobic bacterial culture [54]. MRI Knee Without and With IV Contrast MRI may have a role in the workup of periprosthetic infection. Advances in metal artifact reduction may expand the potential role of MRI. Using metal reduction techniques, Potter and Foo found that infected synovium has hyperintense laminar appearance, distinct from the appearance of particle disease [22,93]. They noted that, in selected cases, MRI may be helpful in detecting extracapsular spread of infection and abscess formation. IV contrast may provide additional benefit in this regard [93]. On the basis of their findings, Plodkowski [94] examined 28 patients with proven infected TKAs and 28 controls with noninfected TKA.