Is obesity an independent risk factor for adverse outcomes after spine surgery?
Obesity is a well-known risk factor for complications following spine surgery. However, obesity is associated with other comorbidities such as diabetes and heart disease that also contribute to complications. In an effort to determine if obesity is an independent risk factor for adverse events after spine surgery, Dr. Seicean and her colleagues from Cleveland used the NSQIP database to analyze about 50,000 patients who underwent spine surgery between 2006 and 2012. They compared rates of adverse outcomes (i.e. major and minor complications, prolonged length of stay, return to OR, discharge to nursing facility, readmission, and mortality) that occurred within 30 days among patients stratified by BMI. Not surprisingly, they found that most adverse events occurred more frequently in obese patients, and the rate of adverse events increased with increasing degrees of obesity. Patients with a BMI over 40 were nearly twice as likely to have a complication compared to patients with a BMI less than 25. They also performed a propensity-score matched analysis in order to control for the effect of comorbidities and found that obesity tended to be an independent risk factor for adverse events only in the morbidly obese (BMI > 40). This indicates that while overweight and mildly obese patients did have an increased risk of adverse events, these differences were likely being driven by comorbidities like diabetes.
This is an interesting study in that it clearly demonstrates that obese patients, especially morbidly obese patients, are at increased risk for complications, but obesity-related comorbidities may be more important than obesity itself. The results need to be considered in light of the limitations inherent in a NSQIP database study, including possible coding inaccuracies, the lack of patient reported outcomes, and a limited, 30 day follow-up period. The most concerning limitation is the inability of the authors to determine exactly what type of procedure was performed. The authors did not control for invasiveness or location of surgery, and it is possible that selection bias played a role, with morbidly obese patients undergoing less invasive procedures. Obesity is likely a more important risk factor in extensive posterior lumbar surgery compared to anterior cervical surgery. This study adds to the body of literature indicating that obesity is a risk factor for adverse events following surgery, and this information should be communicated to obese patients as they make decisions about treatment. Morbidly obese patients should be well-informed about their high risk for suffering a complication if they elect to undergo spine surgery. Additionally, it suggests that “healthy” patients with mild obesity without comorbidities like diabetes, hypertension, and heart disease may not be at significantly increased risk for complications, which can also help to guide treatment decisions.
Please read Dr. Seicean’s article on this topic in the August 15 issue. Does this change how you see the relationship between obesity and complications after spine surgery? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor