Higher BMI may mean more complications for patients with lower back problems who undergo lumbar surgery.
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AAOS Now

Published 1/1/2014
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Peter Pollack

High BMI Increases Risk of Complication for Lumbar Surgery Patients

Multiple complications, longer operating times are of particular concern

Patients with high body mass index (BMI) who undergo lumbar spinal surgery have more postoperative complications than non-obese individuals,” said Rafael A. Buerba, a researcher and MD/MHS candidate at Yale University School of Medicine. Speaking to members of the North American Spine Society during their 2013 annual meeting, he continued, “Complication rates appear to increase substantially for patients who have a BMI greater than 40 kg/m2 (obesity class III).”

Mr. Buerba’s conclusions were based on an analysis of 10,387 patients in the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database. He explained that previous studies looking at the impact of BMI on lumbar surgical outcomes have generally not separated different levels of obesity and have focused on lumbar fusion, not lumbar diskectomies or decompressions, and have demonstrated mixed results regarding complications.

The research team conducted a retrospective cohort analysis of prospectively collected data from the ACS NSQIP on more than 10,000 patients aged 18 years or older, who underwent one of five common lumbar surgery procedures: lumbar anterior fusion, posterior fusion, transforaminal lumbar interbody fusion (TLIF) or posterior lumbar interbody fusion (PLIF), diskectomy, or decompression. They further categorized patients into the following four BMI groups:

  • non-obese—18.5 kg/m2–29.9 kg/m2
  • obese class I—30 kg/m2–34.9 kg/m2
  • obese class II—35 kg/m2–39.9 kg/m2
  • obese class III—greater than 40 kg/m2

“Overall, 17.9 percent of patients underwent posterior fusion, 4.5 percent had anterior fusion, 6.3 percent had TLIP/PLIF, 40.7 percent had diskectomy, and 30.5 percent had decompression,” said Mr. Buerba. “Among all patients, 56.0 percent were non-obese, 25.6 percent were obese class I, 11.5 percent were obese class II, and 6.9 percent were obese class III.”

Compared to non-obese patients, obese patients were more likely to be younger, have a higher American Society of Anesthesiologists classification, have a multilevel procedure, and undergo inpatient surgery. Regarding comorbidities, obese patients of all classes were more likely than non-obese patients to have hypertension requiring medication, dyspnea, and diabetes.

Risks increase with BMI
Mr. Buerba stated that, in unadjusted analyses, as BMI increased, the number of wound, respiratory, urinary, septic, and overall complications, and the number of blood transfusions given also increased. And for all complication categories except blood transfusions, patients in obesity class III had the highest percentage of complications.

“In adjusted analyses, patients in obesity classes I and III showed a significantly increased risk of urinary complications, and patients in obesity classes II and III had a significantly increased risk of wound complications,” he said. “However, only patients in obesity class III had a statistically increased risk of having an extended length of stay, respiratory complications, and one or more complications overall. Compared to non-obese patients, only patients in obesity class III had a longer total operating room time.”

According to Mr. Buerba, all patients with high BMI are at increased risk for complications in lumber surgery, but complication rates sharply increase for patients who are in obesity class III.

“We conclude that the surgeons must be aware of the increased risks of multiple complications for obesity class III patients,” he said.

Mr. Buerba’s coauthors include Michael Fu, Jordan A. Gruskay, Jonathan N. Grauer, MD.

Disclosure information: Messrs. Buerba, Gruskay, and Fu—no conflicts; Dr. Grauer—Stryker, Affinergy, Alphatec, DePuy, Harvard Clinical Research Institute, Powered Research, Smith & Nephew, Transgenomic, Cervical Spine Research Society.

Peter Pollack is electronic content specialist for AAOS Now. He can be reached at ppollack@aaos.org

Bottom Line

  • All obese patients appear to be at greater risk of complication during and after lumbar surgery.
  • Risks appear to substantially increase for patients in obesity class III, especially the risk of multiple complications.
  • Compared to non-obese patients, only patients in obesity class III had longer total operating room times.