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    Working Up the Patient with a Painful Total Knee Arthroplasty

    Infection is the number one cause of failure in total knee arthroplasty (TKA), with approximately 25% of TKA patients needing a revision due to infection in the first few years after surgery.

    Treating an infected TKA is easier once the approach to diagnosis is streamlined, according to Henry D. Clarke, MD, from the Mayo Clinic, Phoenix, Arizona, who shared his insights on the workup for patients with pain following a TKA at the ICJR West meeting in Napa, California.

    Patient complaints of pain are often non-specific, although recent or post-operative drainage raises a red flag for infection. During the evaluation for infection, ask the patient about:

    • Location of the pain
    • Onset: Persistent pain since surgery or sudden pain in a well-functioning knee replacement
    • Severity of the pain
    • Character of the pain: Constant (rest), less mechanical
    • Problems occurring around surgery, such as prolonged drainage, an unusually long time for wound healing, fever and chills
    • Antibiotic history before or after surgery

    Diagnostic tests for periprosthetic joint infection (PJI) include:

    • Preoperative studies
      • Hematologic: white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP). The ESR and CRP are considered reliable indicators of PJI when they are considered together.
      • Aspiration: culture, synovial cell count. Aspirate when the ESR or CRP levels are elevated or when there is a suspicion of PJI after the history and physical.
      • Imaging: radiographs, nuclear medicine scans. Bone scans and nuclear medicine tests are not generally helpful.
    • Intraoperative studies
      • Gram stains are considered unreliable in diagnosing PJI because of the high incidence of false positives.
      • Frozen section is reasonably reliable, depending on the pathologist’s experience.
      • The reliability of cultures can be improved by taking at least three tissues specimens using clean instruments.

    Dr. Clarke’s preoperative workup of potential PJI in his TKA patients complaining of pain:

    Always

    Frequently

    Rarely

    Never

    • History and physical
    • ESR and CRP
    • X-rays (to identify components and other causes of failure, not to diagnose infection)

    Aspiration

    • Cell count and differential (if elevated ESR or CRP or if clinical suspicion of PJI)
    • Two sets of aerobic and anaerobic cultures
    • Fungus culture
    • Crystals
    • Leukocyte esterase
    • Technetium bone scan and indium WBC scan
    • Gram stain

    Dr. Clarke’s intraoperative diagnosis of an infected TKA:

    Always

    Sometimes

    Rarely

    Never

    • Three or more sets of tissue and fluid cultures
    • Frozen section greater than 5 WBCs/high power field
    • Sonification of prostheses for culture (if pre-operative cultures are negative
     
    • Gram stain

    Dr. Clarke made one final note that he will hold pre-operative antibiotics if his working diagnosis before surgery is PJI but the pathogen has not yet been identified.

    Dr. Clarke’s presentation can be found here.