Timing of DVT prophylaxis and risk of postoperative knee prosthesis infection.

This multicenter prospective study was performed to determine risk factors for knee prosthesis infection and the effect of timing doses of prophylactic low-molecular-weight heparins (LMWH) related to time of surgery on the risk of knee prosthesis infection. A total of 5496 consecutive patients who underwent total knee arthroplasty from 2005 to 2006 in 13 orthopedic centers were prospectively followed up for 6 months, and the incidence of knee prosthesis infection was recorded. A case control study was nested in the cohort. Case patients were matched to uninfected (control) patients, and the timing of perioperative LMWH was recorded as the main risk factor. Fifty patients developed postoperative knee prosthesis infection during the follow-up period, yielding an incidence of prosthesis infection of 0.91% (95% CI, 0.68%-1.20%). Forty-four patients were matched to 106 controls. Case patients received the first LMWH dose ±12 hours from the start of surgery more frequently than their control counterparts (odds ratio, 1.5; 95% CI, 0.73-3.0). After adjusting by main risk factors, no statistical association was found between close perioperative timing of LMWH and risk of prosthesis infection. Diabetes mellitus (adjusted odds ratio, 3.2; 95% CI, 1.2-8.8) and wound hematoma (adjusted odds ratio, 4.2; 95% CI, 1.1-16.5) were found to be independent risk factors for prosthesis infection.