[Diagnosis of Periprosthetic Infection - What's Obligation, What's Optional?]

Periprothetic infection after primary or revision arthroplasty is of increasing importance. The incidence of infection in primary arthroplasty is approximately 1 %. Revision arthroplasty has higher infection rates, which increase with the number of revision surgeries. Aim of this Paper: An overview of the current diagnosis of periprosthetic infection.

This selective analysis is based on a lecture by the author at the DKOU 2015.

Periprosthetic infection is taken as having been demonstrated when either two periprosthetic cultures contain the same microorganism, or if there is a fistula communicating with a joint. If only minor criteria are met, the detection of an infection is more difficult. The medical history only provides supporting evidence, especially as regards the course of the pain. Physical examination is more helpful, especially if there is redness, swelling, heat or wound dehiscence. Radiological pathologies, such as osteolysis or bone resorption can only be found in advanced infections. Nuclear medicine scans only possess acceptable sensitivity and specificity in combination with leukocyte scintigraphy. ESR, CRP and leukocyte blood count of the blood are of poor specificity. Important and targeted diagnostic steps include joint aspiration under aseptic conditions, although this exhibits a relatively high rate of false negative results. The conditions for this must be stringently observed. This is usefully complemented by cytological examinations and biopsies for tissue culture. Sensitivity and specificity are then increased. Sonication can significantly enhance the detection of an infection. The leukocyte esterase test is inexpensive and easy to perform and is therefore very much in vogue at the moment; however it is useless if there is contamination with blood. Recent studies indicate that the alpha-defensin test possesses high sensitivity and specificity, but has the disadvantage of being expensive.

In patients with suspected periprosthetic infection, the primary aim is either to exclude an infection, or to detect a pathogen. The essential components are careful evaluation of the medical history, accompanied by imaging and laboratory tests. A critical approach is essential. Joint aspiration has become the gold standard in detecting periprosthetic infections. This should be performed in conjunction with a cytological analysis of the synovial fluid. An improvement in sensitivity and specificity can be archived by taking tissue samples. Sonication significantly improves the results. The latter method, the leukocyte esterase test and the alpha-defensin test are optional. The essential components are a rigorous evaluation, a clear algorithm and interdisciplinary collaboration with microbiologists and possibly infectiologists.