The effect of operative time on in-hospital length of stay in revision total knee arthroplasty

Background: Revision total knee arthroplasty (TKA) is associated with increased rates of infections, readmissions, longer operative times, and lengths-of-stay (LOS) compared to primary TKA. Additionally, increasing operative times and prolonged postoperative LOS arc independent risk factors for these postoperative complications in lower extremity total joint arthroplasty (TJA). This has led to an increased effort to reduce these risk factors in order to improve patient outcomes and reduce cost. However, the relationship between operative time and LOS has not been well assessed in revision arthroplasty. Therefore, the purpose of this study was to: (I) identify predictors of longer operative times; (II) identify predictors of longer LOS; and (III) evaluate the effects of operative time, treated as both a categorical variable and a continuous variable, on LOS after revision TKA. Methods: The NSQIP database was queried for all revision TKA cases (CPT code 27487) between 2008 and 2016 which yielded 10,604 cases. Mean operative times were compared between patient demographics including ago groups, sex, and body mass indexes (BMIs). To determine predictors of LOS, mean LOS were also compared between patient demographics in the same groups. To assess the correlation of operative time on LOS, the mean LOS for 30-minute operative time intervals were compared. Univariate analysis was performed with one-way analysis of variance (ANOVA) and t-tests. A multivariate analysis with a multiple linear regression model was performed to evaluate the association of LOS with operative times after adjusting for patient age, sex, and BMI. Results: The mean LOS for revision TKA was 4 (+/- 3) days. Further analysis showed that young age is associated with increased LOS (P<0.01). An analysis of operative times showed positive correlations with young age, BMI greater than 30 and male sex (P<0.05). The mean LOS of revision TKA patients was found to increase with increasing operative time in 30-minute intervals (P<0.001). Multivariate analysis showed that longer operative times had significant associations with longer LOS even after adjusting for patient factors (beta=0.102, SE =0.001, P<0.001). These results also showed that out of all of the study covariates, operative times had the greatest effect on LOS after revision TKA. Conclusions: Revision TKA is a complex procedure, often requiring increased operative times compared to primary TKA. This study provides unique insight by correlating operative times to LOS in over 10,000 revision TKAs from a nationwide database. Our results demonstrate that out of all the study covariates (age, sex, and BMI), operative times had the greatest effect on LOS. The results from this study indicate that less time spent in the operating room can lead to shorter LOS for revision TKA patients. This relationship further underscores the need for improved preoperative planning and intra-operative efficiency in an effort to decrease LOS and improve patient outcomes.