From the Guidelines
Credit acne around a knee replacement a year after surgery is most likely due to a condition called prosthetic joint infection (PJI), which requires immediate medical attention from an orthopedic surgeon. This serious complication occurs when bacteria colonize the artificial joint, causing inflammation, drainage, and skin changes that may resemble acne. The diagnosis of PJI can be difficult and utilizes many different diagnostic modalities including serologic, radiographic, and microbiologic diagnostic tests, as noted in the study by 1.
Some key points to consider in the diagnosis and management of PJI include:
- The use of serum ESR, CRP, and serum interleukin-6 testing for patients being assessed for peri-prosthetic joint infection, as recommended by the American Academy of Orthopaedic Surgeons (AAOS) guidelines 1
- The importance of joint aspiration, often with fluoroscopy or ultrasound guidance, in diagnosing joint infection after TKA, as found to be extremely useful in the study by 1
- The need for a combination of antibiotics and possibly surgical intervention in the treatment of PJI, with antibiotics alone being sufficient for early or less severe infections, and more severe cases requiring surgical debridement, implant removal, antibiotic spacer placement, and eventual revision surgery, as discussed in the study by 1
The infection likely developed either from bacteria introduced during the original surgery, through bloodstream spread from another infection site, or through a break in the skin near the prosthesis. Risk factors include diabetes, obesity, immune system disorders, and previous joint infections. Do not delay seeking treatment as untreated PJI can lead to implant failure, bone loss, and systemic infection.
In terms of treatment, the study by 1 recommends 4 to 6 weeks of pathogen-specific intravenous or highly bioavailable oral antimicrobial therapy, with the specific treatment depending on the microorganism involved. For example, for Propionibacterium acnes, the preferred treatment is penicillin G 20 million units IV q24 h, with alternative treatments including clindamycin 600–900 mg IV q8 h or clindamycin 300–450 mg PO qid.
Overall, the management of PJI requires a comprehensive approach, including diagnosis, treatment, and prevention of future infections, and should be guided by the most recent and highest quality evidence, such as the study by 1.
From the Research
Causes of Credit Acne in Knee Replacement
- Credit acne, also known as crepitus, is a common complication after knee replacement surgery, characterized by a grinding or crunching sensation in the knee joint 2, 3.
- The exact cause of credit acne is not fully understood, but several factors may contribute to its development, including:
- Infection: Periprosthetic joint infection (PJI) is a leading cause of revision surgery and can lead to credit acne 2, 4.
- Wear and tear: Over time, the artificial joint components can wear out, leading to crepitus and other complications 3.
- Poor implant positioning: Incorrect positioning of the implant can lead to abnormal wear patterns and crepitus 5.
- Soft tissue imbalance: Imbalance in the soft tissues surrounding the knee joint can cause crepitus and other complications 6.
Risk Factors for Credit Acne
- Several risk factors may increase the likelihood of developing credit acne after knee replacement surgery, including:
- Use of vancomycin as a prophylactic antibiotic: While vancomycin has been shown to reduce the risk of PJI, it may also increase the risk of acute kidney injury and other complications 6.
- Pre-existing kidney disease: Patients with pre-existing kidney disease may be at higher risk of developing credit acne due to the increased risk of acute kidney injury 6.
- ASA class: Patients with higher ASA classes may be at higher risk of developing credit acne due to the increased risk of complications 6.