Deep prosthetic infections are a significant cause of failure after arthroplastic surgery. Superficial wound infections are a risk factor for deep infections. We aimed to quantify the risk of deep infection after superficial wound infections, and analyse the microbiology of organisms grown.

We defused Superficial Infection according to the definition used by the Centre for Disease Control, and Deep Infection according to the Swedish Hip Register. We retrospectively analysed the results of 6782 THR and TKRs performed consecutively from 1988–1998. We analysed patient records, radiology and microbiological data. The latter collected prospectively by our infection control team.

We identified 81 (1. 2%) superficial wound infections, however we had to exclude 3 due to poor follow-up. Of the 78 patients studied, mean age was 71 (23–89), 50 were female, 28 male, 41 THR, 37 TKR and follow-up was a mean 49 months (12–130). The majority (81%) of organisms grown in the superficial wound infections were gram positive Staphylococci. These organisms were most frequently sensitive to Erythromycin or Flucloxacillin. All the superficial infections were treated with antibiotics, 66% settled with less than 6 weeks therapy. Deep prosthetic infections occurred in 10% of superficial infections in both THR and TKR. In 80% of cases the organism in the superficial infection caused the deep infection. Wound dehiscence, haematoma, post-op pyrexia and patient risk factors had no affect on onset of deep infection. However patients who had a wound discharge with positive microbiology and those patients in whom there was clinical doubt about the diagnosis of deep infection and thus had antibiotic therapy for more than six weeks had increased risk of deep sepsis.