| Summary: | <p><strong>Aims</strong>: this study compared the patient and microbiological profile of prosthetic
joint infection (PJI) for patients treated with two-stage revision for knee
arthroplasty with that of lower-limb endoprostheses for oncological
resection.
<strong>Patient and methods</strong>:
a total of 118 patients were treated with two-stage revision surgery for infected knee
arthroplasty and lower-limb endoprostheses between 1999 and 2019. A total of 74
patients had two-stage revision for PJI of knee arthroplasty, and 44 had
two-stage revision of oncology knee endoprostheses. There were 68 men and
50 women. The mean ages of the arthroplasty and oncology cohorts were 70.2 years (range of 50–89) and 36.1 years (range of 12–78) respectively (<span class="inline-formula"><i>p</i><0</span>.01). Patient host and extremity criteria were categorized according to the
Musculoskeletal Infection Society (MSIS) host and extremity staging system. The patient microbiological culture, the
incidence of polymicrobial infection, and multidrug resistance (MDR) were
analysed and recorded.
<strong>Results</strong>:
polymicrobial infection was reported in 16 % (12 patients) of knee
arthroplasty PJI cases and in 14.5 % (8 patients) of endoprostheses PJI cases
(<span class="inline-formula"><i>p</i>=0</span>.783). There was a significantly higher incidence of MDR in
endoprostheses PJI, isolated in 36.4 % of cultures, compared with knee
arthroplasty PJI (17.2 %, <span class="inline-formula"><i>p</i>=0</span>.01). Gram-positive organisms were isolated
in more than 80 % of cultures from both cohorts. Coagulase-negative
<i>Staphylococcus</i> (CoNS) was the most common Gram-positive organism, and <i>Escherichia coli</i> was the most common
Gram-negative organism in both groups. According to the MSIS staging system,
the host and extremity grades of the oncology PJI cohort were significantly
worse than those for the arthroplasty PJI cohort (<span class="inline-formula"><i>p</i><0</span>.05).
<strong>Conclusion</strong>:
empirical antibiotic prophylaxis against PJI in orthopaedic oncology is
based upon PJI in arthroplasty, despite oncology patients presenting with
worse host and extremity staging. CoNS was the most common
infective organism in both groups; however, pathogens showing MDR were significantly
more prevalent in oncological PJI of the knee. Therefore, empirical broad-spectrum treatment is recommended in oncological patients following revision
surgery.</p>
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