The Effect of Obesity on Operative Times and 30-Day Readmissions After Anterior Cruciate Ligament Reconstruction

Abstract

Purpose: To understand the effect of obesity on operative times and 30-day readmission rates after arthroscopic anterior cruciate ligament reconstruction (ACLR).

Methods: The American College of Surgeons National Surgical Quality Improvement Program database was queried using Current Procedural Terminology billing codes to identify all patients aged 18 years and older who underwent ACLR between 2007 and 2014. The Student t test was used for continuous variables, and the χ-square or Fisher exact test was used for categorical variables. Multivariate analysis was conducted to identify factors associated with 30-day readmission.

Results: We identified 9,000 patients who underwent ACLR. In the readmission analysis, the total readmission rate was 0.70%. After multivariate analysis, a body mass index (BMI) of 40 or greater was associated with a significantly increased risk of 30-day readmission (odds ratio, 3.06; 95% confidence interval, 1.09-8.57). An operative time of less than 80 minutes was associated with a decreased risk of readmission (odds ratio, 0.40, 95% confidence interval, 0.18-0.92). In the operative-time analysis, the mean operative time was 100.7 minutes. Older age was predictive of decreasing operative time, with the operative time being 32.75 minutes shorter in patients aged 65 years or older than in those younger than 25 years. After multivariate analysis, class II obesity (BMI of 35-39.9) predicted an increase of 7.11 minutes and class III obesity (BMI ≥ 40) predicted an increase of 8.70 minutes compared with normal weight (BMI of 18.5-24.9).

Conclusions: Obesity is associated with longer operative times and increased 30-day readmissions after ACLR, with patients with a BMI of 40 or greater having over 3 times the risk of readmission compared with patients with a normal weight. Male sex, black race, and younger age are all also associated with increased operative times.

Level of evidence: Level III, observational, retrospective cohort study.