Greater BMI Linked to Risk for Revision Procedures Following Lumbar Discectomy

Senior author Kern Singh, MD and SpineUniverse Editorial Board member Todd J. Albert, MD Comment

Card with the letters "BMI" with a stethoscope and measuring tape in the backroundGreater bone mass index (BMI) is independently associated with a greater likelihood of needing a revision procedure following a lumbar discectomy, according to findings in the May issue of Spine.

“The findings of our study suggest that surgeons should consider a patient’s BMI when evaluating them for lumbar surgery,” said senior author Kern Singh, MD, Associate Professor, Co-Director – Minimally Invasive Spine Institute, Rush University Medical Center.

“Overall, lumbar discectomies have been a successful treatment for both obese and non-obese patients,” Dr. Singh explained. “However, recent studies have demonstrated that obese patients have less clinical benefit from operative treatment, with varying evidence for worse outcomes. By identifying BMI’s role in the risk for revision procedures, surgeons can now better counsel their patients on expectations and potential risks of their operation. Preemptive measures might also be taken to better control for postoperative complications associated with this demographic,” Dr. Singh said.

Conflicting Finding on the Role of BMI in Risk for Recurrent/Revision Surgery
Dr. Singh noted that previous studies, including the recent reanalysis of the SPORT trial (Spine Patient Outcomes Research trial), have not shown a link between obesity and the risk of revision procedures.

“However, these studies have made the mistake of not separating obese patients from overweight patients,” Dr. Singh said. “This is a crucial error, as our study identified overweight patients to have a revision rate closer to obese patients than non-obese patients. By grouping overweight patients together with those with normal BMIs, non-obese patients will appear to exhibit higher rates of revision. This inevitably shrouds any potential differences in outcomes between patients with normal and higher BMI. Instead, our study focused on the role of BMI, noting a significant correlation between elevated BMI (including both overweight and obese patients) and revision rates following minimally invasive lumbar discectomy.”

Study Design and Findings
The study involved 226 patients who underwent a single-level minimally invasive lumbar discectomy at Rush University Medical Center. Patients were categorized at normal weight (24.8%), overweight (35.4%), obese (29.2%), or morbidly obese (10.6%). By 2 years postsurgery, 23 patients (10.2%) had undergone a revision procedure.

As shown in the Table, the risk for revision surgery increased with greater BMI. In a multivariate-adjusted analysis, BMI was independently and significantly correlated with the risk for a revision procedure (P=0.038).
Table. Risk for Revision Surgery at 2 Years  Following Lumbar DiscectomyDynamic Classification System for BMI Used
“Many studies have attempted to elucidate the relationship between BMI and outcomes following lumbar surgery,” Dr. Singh said. “This study, however, uniquely approached the issue by breaking down BMI as a dynamic classification system as opposed to obese and non-obese. This provided the opportunity to observe the trends with BMI and the risk of revision. However, future studies with larger sample sizes need to be performed utilizing our method in order to better identify the true relationship between BMI and revision procedures following lumbar discectomy.”

Study Confirms Anecdotal Evidence
“This excellent study confirms what many surgeons may have experienced in their practices: that increased BMI is associated with increased risk of revision surgery, especially in the morbidly obese,” commented Todd J. Albert, MD, Surgeon in Chief and Medical Director Korein-Wilson Professor of Orthopaedic Surgery Hospital for Special Surgery at Weill Cornell Medical College, New York, NY. “As the overall cohort was treated in a minimally invasive manner, differences in infection rate may have been minimized,” Dr. Albert said.

“As we move to a value based economy in health care, it behooves the physician to attend to data such as this,” Dr. Albert added. “If we now will bear the cost and/or penalty for revision and readmission, our interest should be in minimizing this risk and optimizing the patient profile in any way possible.”

Updated on: 06/23/16
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