Higher body mass index is not a risk factor for in-hospital adverse outcomes following total knee arthroplasty.

Purpose: To investigate the association between body mass index (BMI) and perioperative complications until hospital discharge, following primary total knee arthroplasty (TKA).

Methods: This retrospective study reviewed 1665 cases of elective primary unilateral TKA performed between 2006 and 2010, from a prospective secure electronic database. Types of complications, length of operating time, and duration of hospital stay were analyzed in both adjusted (for known confounders) and unadjusted analyses. A further matched analysis was also performed.

Results: In terms of overall complications, there was no statistically significant difference between the BMI categories. When individual obesity category was considered, obese 2 had the lowest odds of developing complications, both with unadjusted (odds ratio (OR): 0.61, 95% confidence interval (CI) 0.41-0.91, p < 0.015) and adjusted regression analysis (OR: 0.65, 95% CI: 0.43-0.99, p = 0.044). Compared to normal weight category, obese class 3 (≥40 kg/m) individuals were at 66% (OR: 0.34, 95% CI: 0.21-0.55) lower (unadjusted) odds of developing cardiac complications (overall p < 0.001). With the matched analysis, compared to normal weight category, obese class 3 (≥40 kg/m) individuals were at a 60% (OR: 0.40, 95% CI: 0.23-0.68) lower (unadjusted) odds of developing cardiac complications (overall p = 0.004). Obese 3 patients had significantly higher operating time compared with other groups ( p < 0.001).

Conclusion: This study did not find a significant association between BMI and increased overall in-hospital medical or surgical complications following primary TKA. Obesity significantly increased the length of operating time.