This retrospective, single-center, observational study was conducted in compliance with the recommendations of the Helsinki declaration. It was approved by the Ethics Committee of the Strasbourg University Hospitals (file no. 2019-26), and all patients gave their written consent. All patients who were operated by two experienced surgeons for aseptic rTHA or rTKA between 1 April 2015 and 31 December 2020 were eligible. Excluded were patients who declined to participate in this study, patients with a suspected periprosthetic infection according to the MusculoSkeletal Infection Society (MSIS) [11], or patients who were minors or legally incompetent. The following preoperative data were compiled: age, gender, weight, height, body mass index (BMI), American Society of Anesthesiologists (ASA) classification [12], National Nosocomial Infections Surveillance (NNIS) risk index [13], and any medical conditions that might contribute to infection (i.e., diabetes, rheumatoid disease, smoking, current immunosuppressive treatment, and obesity).

The surgical procedures were standardized: anterolateral approach to the hip or anteromedial approach to the knee, partial or complete removal of implants and any existing cement at the site of removal, and reconstruction with cemented implants and bone allograft, as needed. The administration of antibiotics was also standardized: routine conventional antimicrobial prophylaxis [cefazolin (Mylan, Saint-Priest, France) 2 or 4 g depending on body weight] during anesthetic induction.

The patients were divided into two consecutive cohorts based on the type of cement used: SALBC with 0.5 g of gentamicin (Palacos R + G ®, Heraeus, Hanau, FRG) in the first cohort (1 April 2015 to 15 February 2018; control group) and DALBC with 1 g of gentamicin and 1 g of clindamycin (Copal G + C®, Heraeus, Hanau, FRG) in the second cohort (16 February 2018 to 31 December 2020; study group).

All patients were followed for a minimum of 24 months. A surgical site infection (SSI) was defined according to the MSIS definition [11]. The occurrence of an SSI was recorded and classified as early (< 3 months after index revision) or late (> 3 months after index revision). The rate of repeat surgery for SSI was monitored. The susceptibility of the bacteria found in the SSI to gentamycin and clindamycin was noted. Any complication or side effect during the postoperative survey was documented, and its relationship to the bone cement was analyzed.

The primary criterion was the raw SSI rate at the 2-year follow-up. The secondary criteria were:

the cumulative SSI rate within 2 years of the revision surgery

the number of repeat surgeries for SSI

the susceptibility of the micro-organisms isolated during subsequent SSI treatment

the influence of preoperative risk factors on the SSI rate and the impact of ABLC.

The collected data were compared between groups with a chi squared test or a Fisher’s exact test and calculation of the odds ratio for qualitative data and by Student’s t test or the Mann–Whitney U test for quantitative data. The effect of prognostic factors was analyzed in the same manner. The cumulative rate of cases without SSI was plotted according to Kaplan–Meier, and the survival rates were compared in the two groups with a log-rank test. All statistical tests were done with a 5% threshold.

Several recent publications have reported that the SSI rate after aseptic rTHA or rTKA ranges from 2% to 15% [14,15,16,17]. The sample size was calculated on the basis of the following assumptions: comparison of two groups, raw SSI rate in control group of 10%, detection of a reduced raw SSI rate of 5% in the study group, alpha risk of 0.05, and beta risk of 0.20. According to this calculation, a minimum of 138 patients per group was needed.