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The Spine Blog

Friday, November 2, 2012

Obesity and Outcomes in Spinal Stenosis and Degenerative Spondylolisthesis

With the obesity epidemic upon us, surgeons oftentimes find themselves in a quandary when deciding how to counsel obese patients about their risks of complications and likely outcomes while considering treatment for spinal stenosis (SpS) and degenerative spondylolisthesis (DS). Prior studies have shown mixed results, with the general trend suggesting that obese patients treated surgically have a higher complication rate but similar long-term outcomes compared to non-obese patients. In the November 1 issue, Dr. Rihn and his co-investigators from the Spine Patient Outcomes Research Trial (SPORT) reported surgical and nonoperative outcomes for SpS and DS stratified by obesity status, using BMI of over 30 as the definition of obesity. They showed no significant differences between the obese and non-obese groups in terms of complications or surgical outcomes in the SpS cohort, which was treated primarily with laminectomy without fusion. In contrast, the obese DS patients treated surgically—the majority of whom underwent fusion--had more blood loss, longer OR times, and higher infection and re-operation rates compared to the non-obese cohort. However, the long-term surgical outcomes for the DS patients tended to be similar across the two BMI groups, with the exception of the SF-36 Physical Function score, on which the obese group improved approximately 5 points less. The most striking finding of the paper was the very poor nonoperative outcomes for the obese patients in both the SpS and DS cohorts, a finding which has not been previously reported. Given the similar surgical outcomes and markedly worse nonoperative outcomes for the obese patients, obese patients had a greater treatment effect of surgery (the difference in improvement between surgery and nonoperative patients) on some outcomes.


How should these results impact treatment decision making in obese patients with SpS or DS? While it is somewhat counterintuitive, the fact that the obese patients have a greater treatment effect of surgery implies that, if anything, surgery should be considered even more strongly in this population. Prior studies that showed worse surgical outcomes in obese patients did not consider their nonoperative outcomes, which could lead surgeons to erroneously steer obese patients away from surgery. The unique aspect of SPORT is that nonoperative outocomes were included, and this allows for patients and surgeons to have more complete information as they attempt to make an informed treatment decision. Comparison of surgical outcomes between obese and non-obese patients does not help the individual making the treatment decision as they are not choosing between being obese and being non-obese. The relevant comparison is between likely surgical and non-operative outcomes for the individual patient, which is characterized by the treatment effect of surgery. The more accurately this can be predicted based on the patient’s specific characteristics, the more helpful it will be in guiding decision making. Does this paper indicate that all obese patients with SpS and DS who meet the indications for surgery should choose surgical treatment? Obviously not. The data indicate that obese patients who undergo fusion for DS had a much higher complication rate, including infection and re-operation rate. Obese patients need to understand the increased risks they face with surgery, and only they can decide if the likely benefit of surgery outweighs these risks. As more data emerges from SPORT evaluating the treatment effect of surgery stratified by specific patient characteristics, it becomes clear that many variables traditionally thought of as markers for poor surgical outcomes are actually associated with even worse nonoperative outcomes. For example, DS patients taking opioids were found to have a greater treatment effect of surgery than patients not taking opioids due to the extremely poor nonoperative outcomes among patients taking opioids.1 In general, the data suggest that while some patient characteristics might predict less improvement with surgery, almost all patient subgroups improved more with surgery than with nonoperative treatment. These data can be used to counsel patients so they have reasonable expectations about their likely outcomes with surgical or nonoperative treatment. In the end, the appropriate treatment choice is the one made by a fully informed patient after going through a thorough shared-decision making process with their doctor.


Please read Dr. Rihn’s article on this topic in the November 1 issue. Does this article affect how you will counsel obese SpS and DS patients about their likely surgical and nonoperative outcomes? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor




1.            Pearson A, Lurie J, Tosteson T, Zhao W, Abdu W, Weinstein J. SPORT Predictors of Treatment Effect in Degenerative Spondylolisthesis. Presented at the Annual Meeting of the International Society for the Study of the Lumbar Spine; 2012; Amsterdam.