Expanded Gram-Negative Antimicrobial Prophylaxis Reduces Surgical Site Infections in Hip Arthroplasty

A first-generation cephalosporin is the recommended antibiotic prophylaxis for implants. However, this standard does not address the increasing prevalence and virulence of gram-negative pathogens infecting patients. We found that gram-negative bacilli caused 30% of our surgical site infections (SSIs) following hip procedures, whereas only 10% of knee SSIs were caused by gram-negative bacilli. To address this, we instituted Expanded Gram-Negative Antimicrobial Prophylaxis (EGNAP) for our hip arthroplasty patients. The purpose of this study is to measure the effect of EGNAP on the SSI rates following primary total hip arthroplasty.

The study consisted of 10,084 total patients. Before July 2012, all patients were administered 1 g of cefazolin. After July 2012, our protocol was adjusted by adding the EGNAP with either gentamicin or aztreonam to hip patients (group 1) and not to the knee arthroplasty patients (group 2).

Group 1 consisted of the 5389 primary hip arthroplasty patients. Of these patients, 4122 (before July 2012) did not receive weight-based high-dose gentamicin and 1267 (after July 2012) did. Before the introduction of EGNAP, group 1 SSI rate was 1.19% (49/4122). After July 2012 when EGNAP was added, the overall group 1 SSI rate decreased to 0.55% (7/1267) (P = .05). During the study period, there was not a significant difference in SSI rate of knee arthroplasty (group 2): 1.08% vs 1.02% (P = .999).

The addition of EGNAP for hip arthroplasty is a safe and effective method to decrease SSIs.

Level of Evidence: III. Case-control study.