A 63-year-old man with a history of hypertension, type 2 diabetes, and severe osteoarthritis underwent a right total knee arthroplasty 3 months earlier. He comes to his primary care physician with persistent pain and swelling of the right knee. The patient has pain with activity and at rest, with the most significant pain associated with weight bearing. He has no fevers, chills, nausea, vomiting, or diarrhea. He goes to rehabilitation but his participation has been limited over the past week due to persistent pain.
His temperature is 37.1 C (98.7 F), blood pressure is 114/74 mm Hg, pulse is 86/min, and respirations are 18/min. Examination shows a moderately swollen right knee with decreased range of motion. The surgical scar is intact without surrounding erythema. Examination of the left knee is within normal limits.
An x-ray of the knee reveals an intact prosthesis. Laboratory tests, including complete blood count, electrolyte panel, C-reactive protein, and erythrocyte sedimentation rate, have been ordered.
Which of the following is the best next step in management of this patient's condition?

Question

A 63-year-old man with a history of hypertension, type 2 diabetes, and severe osteoarthritis underwent a right total knee arthroplasty 3 months earlier.  He comes to his primary care physician with persistent pain and swelling of the right knee.  The patient has pain with activity and at rest, with the most significant pain associated with weight bearing.  He has no fevers, chills, nausea, vomiting, or diarrhea.  He goes to rehabilitation but his participation has been limited over the past week due to persistent pain.
His temperature is 37.1 C (98.7 F), blood pressure is 114/74 mm Hg, pulse is 86/min, and respirations are 18/min.  Examination shows a moderately swollen right knee with decreased range of motion.  The surgical scar is intact without surrounding erythema.  Examination of the left knee is within normal limits.
An x-ray of the knee reveals an intact prosthesis.  Laboratory tests, including complete blood count, electrolyte panel, C-reactive protein, and erythrocyte sedimentation rate, have been ordered.
Which of the following is the best next step in management of this patient's condition?

Quizplus · Accepted Answer

This patient's increased knee pain and swelling 3 months after arthroplasty is concerning for either aseptic mechanical complication of the prosthesis or early-onset prosthetic joint infection (PJI). Mechanical complications typically present with pain associated with weight bearing or activity. PJI often presents with persistent pain and other localized or systemic symptoms of infection (eg, joint effusion, wound drainage, fever, erythema, induration, edema). PJI can present as early (< 3 months), delayed (3-12 months), or late onset (> 12 months) after surgery. Although plain films can be helpful in establishing the diagnosis of PJI, the sensitivity and specificity of x-ray findings are limited. The absence of x-ray findings should not deter further consideration of PJI in the appropriate setting. Diagnostic arthrocentesis should be performed in patients with suspected PJI unless open surgical drainage is anticipated or an obvious sign of infection, such as a sinus tract, is present. Synovial fluid analysis should include a cell count and differential and Gram stain and culture for aerobic and anaerobic organisms. Erythrocyte sedimentation rate and C-reactive protein can be useful adjunctive tests in establishing the diagnosis. Blood cultures should also be performed. Early-onset PJI usually improves with surgical debridement followed by prolonged antibiotics. Delayed and late onset may also require prosthesis removal if debridement shows an infected prosthesis. (Choice B) Unless there are clear signs of sepsis, the use of antibiotics should follow arthrocentesis to maximize the yield of synovial fluid culture and direct antibiotic therapy. This patient appears clinically stable and should first undergo arthrocentesis. (Choice C) MRI can be done only in patients with titanium or tantalum prostheses but is still not as sensitive as arthrocentesis. (Choice D) Naproxen with close follow-up is indicated for symptomatic relief in noninfectious causes of joint pain (eg, bursitis). Although naproxen may also help this patient's symptoms, he should first undergo arthrocentesis to evaluate for PJI. (Choice E) Technetium 99m colloid bone scan is nonspecific and may show high false-positive results in the early months after prosthetic joint implantation due to periprosthetic bone remodeling. Educational objective: Prosthetic joint infection should be considered in patients with increasing pain after joint replacement. Arthrocentesis establishes the diagnosis. Treatment involves surgical debridement (or removal in delayed or late-onset cases) followed by a prolonged course of intravenous antibiotics. __________ References: Diagnosis and management of prosthetic joint infection: clinical practice guidelines by the Infectious Diseases Society of America. (http://www.ncbi.nlm.nih.gov/pubmed/23223583) Prosthetic joint infection: diagnosis and management. (http://www.ncbi.nlm.nih.gov/pubmed/21905787)

A 63-Year-Old Man with a History of Hypertension, Type 2