Infection after total knee arthroplasty difficult to treat effectively

Infections resulting from total knee arthroplasty can be potentially disastrous, especially if the infection recurs following initial treatment. Thus, it is crucial to handle an infection as thoroughly as possible while still retaining the patient’s function, said Robert T. Trousdale, MD, during a presentation at Orthopedics Today Hawaii 2009.

“There are a lot of things that we can do in the operating room during the operation to help decrease our risk of infection,” he said. “The rate of infection after total knee arthroplasty has decreased over the last three decades, but it remains a significant problem as more and more patients are undergoing the procedure.”

Trousdale outlined the goals of infection treatment, including the eradication of the infection, alleviation of the patient?s pain and restoration of any function the patient previously maintained. Treatment options include amputation, arthrodesis, reimplantation, resection arthroplasty, debridement and suppression.

Amputation offers the best chance of curing infection after a total knee replacement, Trousdale said, but even that approach cannot guarantee a 100% success rate. Worse, amputation offers the absolute worst functionality of any treatment option.

Reimplantation provides the best potential function, but that functionality comes at the cost of the highest reinfection rate among any available treatments, he noted. Arthrodesis is more capable of curing the infection, but offers less functionality than reimplantation.

Trousdale said understanding the risks inherent in reinfection is imperative for the patient.

“All decisions should be made with the knowledge that if the patient becomes reinfected, salvage becomes very difficult,” he said.

Trousdale cited 24 patients of his who experienced a reinfection after reimplantation. Of those 24, 10 received fusions, five went on suppressive antibiotics, four had to undergo amputation, three dealt with persistent pseudoarthrosis, one had a resection and only one had a successful reimplantation. These patients averaged 9.3 surgical procedures per knee.

While reimplantation offers the best chance for optimal functional outcome, there are still many controversies and questions surrounding its use, Trousdale said. For example, the optimal duration of staging is unknown.

“We’ve seen it go up to 1 year,” he said.

Other questions and controversies include the optimal duration and route of antibiotic delivery, the efficacy of antibiotic spacers and bone cement, the role of spacer blocks/PROSTALAC (prosthesis of antibiotic-loaded acrylic cement) on functional outcome, and the use of allograft in the face of previous infection.

Indications that a new implant might work include good bone stock, adequate soft tissues and immunocompetence, Trousdale said. Contraindications include persistent infection, an immunocompromised host, extremely poor bone stock and extremely poor soft tissues.

Reference:
Trousdale RT. Prevention, diagnosis and treatment of infection. Presented at Orthopedics Today Hawaii 2009. Jan. 11-14, 2009. Kohala Coast, Hawaii.