Is Operative Time a Predictor for Post-Operative Infection in Primary Total Knee Arthroplasty?

BACKGROUND: The purpose of this study is to identify factors affecting operative times and to evaluate the associations of operative times with prosthetic joint infections (PJIs) and surgical site infections (SSIs) in primary total knee arthroplasty. METHODS: A total of 11,840 primary total knee arthroplasties with a mean 2-year post-operative follow-up were studied. Operative times were analyzed both as categorical and continuous variables. Associations with PJIs and SSIs were evaluated with univariate and multivariate analyses to adjust for gender, age, body mass index, Charlson Comorbidity Index, year of surgery, antibiotic cement use, and hospital/surgeon volume. RESULTS: The longest cases (>121 minutes) were associated with patients who were younger (P < .001) and had a higher body mass index (P < .001). PJI rates were higher in cases >121 minutes (1.4%) compared to those <85 minutes (0.3%, P < .001). SSI rates were also highest (3.8%) in cases >121 minutes (P < .001). Cases complicated by PJIs (135 ± 47 minutes) had longer mean operative times compared to non-infected cases (105 ± 32 minutes, P < .001). Patients with subsequent SSIs also had longer mean operative times (P < .001). Multivariate analyses revealed an 18% increased risk for PJIs and an 11% increased risk for SSIs for every 15-minute increase in operative time. CONCLUSION: Identifying risk factors for infection that are as easily measurable and modifiable as procedure duration can aid in risk-stratifying post-operative surveillance. This study demonstrated that longer operative times were an independent predisposing factor for both PJIs and SSIs even after accounting for patient and procedure-related factors.

Effect of Antibiotic-Impregnated Bone Cement in Primary Total Knee Arthroplasty.

BACKGROUND: The purpose of this study is to evaluate the effect of commercially available antibiotic-impregnated bone cement (AIBC) on (1) prosthetic joint infections (PJIs) and (2) surgical site infections (SSIs) after primary total knee arthroplasty (TKA). METHODS: A review of primary TKAs between 2014 and 2017 from an institutional database was conducted. This identified 12,541 cases which were separated into AIBC (n = 4337) and non-AIBC (8,164) cohorts. Medical records were reviewed for PJIs and SSIs (mean 2-year postoperative period). Infection rates between the cohorts were compared with univariate analyses followed by subanalysis of high risk patients (defined as having 2 or more of the following characteristics: >65 years, body mass index >40, or Charlson Comorbidity Index score >3). To control for confounders, multivariate analyses were performed with regression models adjusted for age, gender, body mass index, comorbidities, year, operative times, and lengths of stay. RESULTS: On univariate analysis, PJI rates were higher in the AIBC cohort (1.0%) compared to the non-AIBC cohort (0.5%, P < .001). Subanalysis of the high risk patients also showed that PJI rates were higher in the AIBC cohort (1.9% vs 0.6%, P < .01). After adjusting for potential confounders, no significant associations between PJIs and AIBC use were found (odds ratio 1.4, 95% confidence interval 0.9-2.3, P = .133). Similarly, no significant differences in SSI rates were observed between the AIBC (2.9%) and non-AIBC cohorts (2.4%, P = .060) and no significant associations between SSIs and AIBC were found with multivariate analysis (odds ratio 1.0, 95% confidence interval CI 0.8-1.3, P = .948). CONCLUSION: This study found that there was no clinically or statistically significant decrease in infection rates with AIBC in primary TKAs.

Postoperative Infection in Cementless and Cemented Total Knee Arthroplasty: A Propensity Score Matched Analysis.

The ongoing debate on fixation in total knee arthroplasty (TKA) has become increasingly relevant with its increased use in a younger patient population and the advent of novel cementless prostheses. Recent literature suggests modern cementless implants are comparable to their cemented counterparts in terms of survivorship and functional outcomes. What has not been well-assessed is whether the two modalities differ with respect to infection rates which was the purpose of this study. Specifically, a propensity score matched study population was used to compare: (1) overall infection; (2) prosthetic joint infection (PJI); and (3) surgical site infection (SSI) rates between cementless and cemented TKAs. Using a large institutional database, 3,180 consecutive primary TKAs were identified. Cementless and cemented TKA patients were propensity score matched by age (p = 0.069), sex (p = 0.395), body mass index (BMI; p = 0.308), and Charlson's comorbidity index (CCI) score (p = 0.616) in a 1:1 ratio. Univariate analysis was performed to compare 2-year overall infection rates. Infections were further analyzed separately as PJIs (deep joint infections requiring surgery) and SSIs (skin/superficial wound infections). Multivariate logistic regression was performed to evaluate infection incidences after adjusting for procedure-related factors (i.e., operative time, hospital volume, and surgeon volume). There were no significant differences between the matched cohorts in terms of overall infection rates (3.8 vs. 2.3%, p = 0.722), as well as when PJI (p = 1.000) and SSI (p = 1.000) rates were analyzed separately. Multivariate analysis revealed no significant differences in overall postoperative infection rates (p = 0.285), PJI rates (p = 0.446), or SSI rates (p = 0.453) even after adjusting for procedure-related factors. There is increasing literature investigating various outcomes demonstrating the comparable efficacies of cementless versus cemented TKAs. To the best of the author's knowledge, this was the first matched case-control study to directly compare their post-operative infection rates. The findings from this study show that post-operative infection rates were similar between fixation modalities even after accounting for a range of patient- and procedure-related factors.