The sustained benefits of gram-negative antimicrobial prophylaxis in total hip arthroplasty: a 10-year retrospective analysis.

Background: 10 years after changing our institution's total hip arthroplasty (THA) preoperative antibiotic prophylactic protocol by adding gram-negative (GN) coverage, this study aimed to assess the impact of adding GN specific coverage (GNSC) prior to THA on periprosthetic joint infection (PJI) rates.

Methods: This was a retrospective case-control study of 14,598 patients who underwent primary, elective THA between July 2012 and January 2022, with minimum 1-year follow-up. All patients were under perioperative antibiotic protocol that included GNSC with either weight-based gentamicin or aztreonam (+GNSC) and were compared to a historical control group of patients for which the antibiotic prophylactic protocol did not include GNSC (-GNSC). PJI and nephrotoxicity rates, as well as the severity of nephrotoxicity according to the RIFLE criteria, were compared between the study populations and 4122 controls.

Results: Proportions of GN-related PJIs among culture-positive (13.70 vs. 26.53%, p = 0.076) and all PJIs (10.64 vs. 26.53%, p = 0.014) were lower for +GNSC patients, while the proportion of PJIs caused by a gram-positive bacteria were similar between groups (87.67 vs. 83.67%, p = 0.532). While the +GNSC group have significantly higher rates of nephrotoxicity (2.87 vs. 1.78%, p = 0.003), the rates of kidney injury (0.39 vs. 0.39%, p = 0.998) and kidney failure (0.17 vs. 0.16%, p = 0.567), which are the two more severe forms of nephrotoxicity, were comparable between the groups.

Conclusions: The addition of gentamicin or aztreonam prior to THA reduces the incidence of GN-related PJIs. Increased nephrotoxicity rates were limited to the mildest form, usually associated with reversibility and favourable outcomes.