The Insall Award paper - Infection in total knee replacement - A retrospective review of 6489 total knee replacements

Six thousand four hundred eighty-nine knee replacements were done in 6120 p atients at the authors' institution between 1993 and 1999. Operations were done in a theater with vertical laminar How and with the surgical team usin g body exhaust suits. Of these knee replacements, 116 knees became infected and 113 were available for followup. One hundred of the infections occurre d in patients undergoing primary knee replacement, whereas the remaining in fections occurred in patients undergoing revision knee replacement. Ninety- seven of these knees (86%) had deep periprosthetic infections and the remai ning 16 knees had superficial wound infections. One third of the deep infec tions occurred within the first 3 months after surgery and the remaining 2/ 3 occurred after 3 months. The overall early deep infection rate for patien ts undergoing a primary knee replacement was 0.39%, whereas the rate for pa tients undergoing a revision knee replacement was 0.97%. A cohort of noninf ected knee replacements from patients matched for gender, age, and month of surgery was used as a control group. Those comorbidities that were statist ically significant in increasing the risk of infection were prior open surg ical procedures, immunosuppressive therapy, poor nutrition, hypokalemia, di abetes mellitus, obesity, and a history of smoking. Patients undergoing rev ision procedures had a statistically higher risk of infection than did pati ents undergoing primary surgeries. If the surgery took longer than 2.5 hour s, the risk of infection was increased significantly. There was no change i n the infection rate when the perioperative antibiotic prophylaxis was decr eased from 48 to 24 hours after surgery. The predominant infectious organis ms were gram-positive (Staphylococcus aureus, Staphylococcus; epidermidis, and Streptococcus Group B). Twenty percent of the knees that were infected clinically had no organisms that could be identified. In each case, the pat ient had been treated empirically at another institution with antibiotics b efore a culture of the joint was obtained.