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.