Outcome of retained two stage exchange arthroplasties in the treatment of infected total knee replacement

ABSTRACT

We studied the outcome of retained two stage exchange arthroplasties that were implanted as a method of treatment of infected total knee replacements. Among a group of 31 infected knees, we were left with 18 patients that were followed for minimum of 2 years. The mean age distribution at the last follow up was 69 years, with an equal distribution between males and females. Sixteen patients [88.8%] had their primary replacement for primary osteoarthritis and 2 patients [11.2%] were rheumatoid patients. Presentation varied between pain, swelling, warmth, stiffness and /or reduction in mobility. The shortest period of presentation with infection following the primary knee replacement was two weeks and the longest was 115 months, with an average of 21.3 months. A full diagnostic workup was carried out before an infection diagnosis could be established. Patients were subjected to the well known two stage exchange arthroplasty protocol with a first stage debridement and removal of prosthesis and all cements, followed by insertion of a cement spacer. The first stage was followed by a period of antibiotics of a minimum of 6 weeks until all laboratory evidence of infection has been cleared, with clinical quiescence. This was followed by a second stage revision total knee with insertion of a new prosthesis. The shortest period of follow up was 2 years and the longest was 5.5 years, with an average follow up of 3.1 years. At the last follow up, patients were evaluated based on the Knee Society Scoring System. The lowest knee score was 18 and the highest was 94 with a mean of 68.2. The lowest functional score was 5 and the highest was 100 with a mean functional score of 56.1. It was observed that the functional score was much lower than the knee score due to associated general ill health of this group of elderly patients. However, the results obtained were generally felt to be superior to other salvage procedures namely, arthrodesis, resection arthroplasty or amputation which are generally left for failed other modalities of treatment. Still, there is a lot or room for improvement if more laboratory and microbiological facilities were available, in a specialized centre dedicated for the management of these difficult cases