Is Obesity a Risk Factor for Adverse Events After Knee Arthroscopy?

Purpose: To evaluate how body mass index (BMI) affects rates of 30-day complication, hospital readmissions, and mortality in patients undergoing knee arthroscopy.

Methods: Patients undergoing knee arthroscopy procedures between 2006 and 2013 were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Patient demographics and preoperative risk factors including BMI were analyzed for postoperative complications within 30 days. Cochran-Armitage testing was performed to detect differences in complication rates across BMI categories according to World Health Organization classification. The independent risk of BMI was assessed using multivariate regression analysis.

Results: Of 41,919 patients with mean age 48 years undergoing knee arthroscopy, 20% were classified as normal weight (BMI 18.5 to 24), 35% overweight (BMI 25 to 29), 24% obese class I (BMI 30 to 34), 12% class II (BMI 35 to 40), and 9% class III (BMI ≥40). Risk of complication increased significantly with increasing BMI (normal: 1.5%, overweight: 1.6%, obese class I: 1.7%, obese class II: 1.8%, obese class III: 1.9%, P = .043). On multivariate analysis, there was no increased risk of postoperative complication directly attributed to patient BMI. Independent risk factors for medical and surgical complications after knee arthroscopy included American Society of Anesthesiologists (ASA) rating (class 4 v class 1 odds ratio [OR]: 5.39 [95% confidence interval: 3.11-9.33], P < .001), functional status for activities of daily living (dependent v independent OR: 2.13 [1.42, 3.31], P < .001), history of renal comorbidity (presence v absence OR: 5.10 [2.30, 11.29], P < .001), and previously experienced history of wound infection prior to current surgery (presence v absence OR: 4.91 [2.88, 8.39], P < .001).

Conclusions: More than 40% of knee arthroscopy patients qualify as obese. Although univariate analysis suggests that obesity is associated with increased postoperative complications within 30 days of surgery, BMI alone does not predict complications. Independent predictors of complications include patients with high ASA classification, dependent functional status, renal comorbidities, and a recent history of wound infection.

Level of evidence: Level IV, prognostic case series.