Figure 1. Anteroposterior radiograph of the right knee.
Figure 2. Lateral radiograph of the right knee.
A 71-year-old man presents to the office with right knee pain and swelling after he underwent knee replacement 3 months earlier. Anteroposterior and lateral radiographs are obtained (Figures 1 and 2). On examination, the knee is warm and erythematous; +1 effusion is noted. Aspiration of the synovial fluid reveals turbid fluid with a white cell count of 80,000 cells/µL.
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Postoperative total knee infection is one of the most serious complications following knee arthroplasty and may be experienced by up to 5% of patients despite strict adherence to an aseptic technique and perioperative antibiotic use.1 When patients present with a warm, swollen knee and fever, periprosthetic joint infection should be suspected. The first diagnostic step is to assess inflammatory markers such as serum erythrocyte sedimentation rate, C-reactive protein, and complete blood count.2 If these inflammatory markers are elevated, joint aspiration should be performed. The aspirated synovial fluid should be sent for analysis to identify the pathogen and confirm the diagnosis; elevation >1100 cells/µL and polymorphic neutrophil count >64% raise suspicion of periprosthetic infection.
Treatment of a periprosthetic infection remains controversial. The most common treatment choices include irrigation and debridement with polyethylene exchange, 1-stage revision arthroplasty, or 2-stage revision arthroplasty. Irrigation and debridement usually involves knee arthrotomy, polyethylene liner exchange, and 3 L of irrigation before wound closure. A 1-stage revision, which is the least used of the 3 choices, includes removal of implants, irrigation and debridement, then re-implantation of the components. A 2-stage revision includes removal of all implants, placement of an antibiotic-impregnated cement spacer, and administration of intravenous antibiotics. At 3 months the cement spacer is removed and, if all intraoperative cultures remain negative, the knee is revised. The most successful treatment option of the choices provided is the 2-stage procedure. Irrigation and debridement has a 71% to 79% success rate for avoiding future revision surgery for infection.1 The success rate for 1-stage revision is 82% to 87%, and the success rate for 2-stage revision is 87% to 90%.1
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).
1. Leta TH, Lygre SH, Schrama JC, et al. Outcome of revision surgery for infection after total knee arthroplasty: results of 3 surgical strategies. JBJS Rev. 2019;7(6):e4.
2. Clark CR. Periprosthetic infection in total knee arthroplasty. JBJS website. https://www.jbjs.org/summary.php?id=219&native=1. Published December 3, 2018. Accessed September 16, 2019.
This article originally appeared on Clinical Advisor