Deep infection after total hip replacement: a method for national incidence surveillance.

Lindgren, Viktor; Gordon, Max; Wretenberg, Per; Kärrholm, Johan; Garellick, Göran

OBJECTIVE The purpose of this study was to estimate the incidence of deep periprosthetic joint infections (PJIs) after primary total hip replacement (THR) in Sweden prior to the introduction of a national initiative to reduce these infections. DESIGN Prospective open cohort study with 2 years follow-up of each subject. SETTING All THR-performing clinics in Sweden. METHODS All patients registered for a primary THR in the Swedish Hip Arthroplasty Register between July 1, 2005, and December 31, 2008, were selected for the study (45,531 patients with 49,219 THRs) and were matched with the Swedish Prescribed Drug Register. All patients with a minimum of 4 weeks of continuous outpatient antibiotic treatment within 2 years after their primary THR (1,989 patients with 2,219 THRs) were selected for a medical records review, and the number of cases with PJI was determined. RESULTS The cumulative incidence of PJI within 2 years after primary THR was 0.9% (95% confidence interval, 0.85-1.02; n = 443), and 405 of these had been reoperated. The incidence rate of PJI for the first 3 months was 5 per 10,000 THR-weeks and, thereafter, 0.3 per 10,000 THR-weeks. Staphylococcus aureus and coagulase-negative staphylococci were the most common bacteria isolated. CONCLUSIONS This study describes a new method of national postoperative infection surveillance. The incidence is similar to previous smaller reports and is useful for monitoring changes over time to evaluate the national initiative to reduce infections.