Emerging Management of Obesity in Spine Surgery

The worldwide obesity rate has tripled since 1975, and current trends suggest rates will continue to rise. According to the World Health Organization, as of 2016, 650 million adults were estimated to be categorized as obese, with a body mass index (BMI) of 30 kg/m2 or greater. Its relevance is front and center, as comorbidities such as type 2 diabetes, hypertension, heart disease, and stroke are among the leading causes of preventable death and are all linked to obesity.[1] Furthermore, obesity places a strain on the healthcare system, incurring nearly $190 billion each year in healthcare expenditure.[2]

Similarly, low back pain is a common complaint among obese patients and ranks as the fifth most common reason for a medical visit in the United States.[3] As such, obesity has been suggested to play a role in various spine disorders, including symptomatic degenerative disc disease, spondylolisthesis, and spinal stenosis.[4] While increased biomechanical loads impart abnormal stresses to the spine, obesity and its correlation to spinal disorders is multifactorial and likely involves a component of chronic inflammation, reduced blood flow, and genetic and environmental factors. Studies have even suggested upregulation of adipokines such as leptin, which is linked to osteoarthritis, disc degeneration, and radiculopathy.[5]

Unfortunately, the literature is fraught with evidence suggesting inferior outcomes following spine surgery in obese patients. Aside from the added complexity of performing spine surgery, obesity has been linked to increased overall cost of surgery, blood loss, operative time, postoperative infections, risk of thromboembolism, narcotic consumption, and all-cause mortality.[6–12] Minimally invasive techniques can often mitigate some of these risks, thus allowing obese patients to still benefit from spine surgery.[13]

Obesity is clearly a keystone surrogate for overall patient health and links to various comorbidities as previously mentioned. It is no surprise, therefore, that preoperative weight loss can significantly improve outcomes and reduce the risk of complications after surgery; thus, it should be at the forefront of preoperative optimization.[14] Surgeons will often offer recommendations for weight loss leading up to surgery, such as providing online and in-print educational materials or recommending weight loss diets, but they are rarely successful in achieving meaningful weight reduction.[15,16]

More aggressive means of weight loss, such as bariatric surgery, have been well-studied in the literature. In patients with a BMI >30 kg/m2 who are appropriate candidates, bariatric surgery has demonstrated cost effectiveness in patients undergoing elective spinal fusion.[17] A meta-analysis of 183,570 obese patients undergoing elective spine surgery demonstrated a significant reduction in gastrointestinal, renal, neurologic, and thromboembolic complications, as well as all-cause mortality,[18] though the risk of complications is still higher than in patients with a normal BMI.[19]

While weight loss undeniably can reduce the risks of postoperative complications, it may also improve axial low back pain and radiculopathy.[5] However, there are fewer published data evaluating the timeline in which rapid weight loss occurs. A database study by Rudy et al of 39,742 obese patients undergoing lumbar fusion evaluated a cohort of patients who had rapid weight loss leading up to surgery. The authors noted a significant increase in length of stay, surgical site infections, thromboembolism, and the need for transfusion.[20]

While the study is intriguing, Rudy et al failed to evaluate the means of weight loss. Historically, bariatric surgery and incidental side effects from various medications were the only means of rapid weight loss. However, there has been a recent uptick in medications approved for weight loss, which may play a significant role in spinal surgery.

Saxenda (liraglutide) was the first medication approved by the US Food and Drug Administration (FDA) in December 2014 for the treatment of weight loss. However, its adoption was not widespread and there was stigma surrounding a medication solely approved for weight loss. Three years later, the FDA approved Novo Nordisk’s once-weekly Ozempic (semaglutide) for type 2 diabetes. During its use, increasing data began to suggest prolonged and maintained weight loss after initiation of therapy. A randomized controlled trial published in the New England Journal of Medicine evaluated 2.4 mg of semaglutide administered once-weekly in 1,961 patients and found an average weight loss of 15.3 kg at 68 weeks with only mild side effects.[21] Additional data supported using a similar dosage as well as a lower dosage of 1.7 mg weekly. Finally, a randomized controlled trial comparing liraglutide and semaglutide found the latter to be safe and effective in treating weight loss.[22]

GLP-1 (glucagon-like peptide-1) is a hormone that is naturally produced by the body to regulate blood sugar levels. It works by stimulating the release of insulin and slowing down the rate at which food is emptied from the stomach. GLP-1 receptor agonists (GLP-1 RAs), like semaglutide, mimic the effects of GLP-1 by binding to GLP-1 receptors in the body and activating them.

Since its adoption, the use of semaglutide has skyrocketed, especially following public appraisal by billionaires such as Elon Musk. This “celebrity” medication quickly made headlines and filled the homes of the public, raising controversy while creating a nationwide shortage. Therefore, variations in semaglutide and other GLP-1 RAs have flooded the FDA-approval queue. Wegovy (semaglutide) became the next medication approved by the FDA on June 4, 2021, with an indication for weight loss in both adults and adolescents older than 12 years. [23] The most recently approved medication, Mounjaro (tirzepatide, Eli Lilly), received accelerated approval on May 13, 2022, but it is being sold at a higher overall cost. In various clinical trials, tirzepatide was found to delay gastric emptying, lower fasting and postprandial glucose concentration, decrease food intake, and reduce body weight in patients with type 2 diabetes. Furthermore, tirzepatide was noninferior and superior to semaglutide at all doses.[24]

Other classes of medications, such as sodium-glucose co-transporter 2 inhibitors, including canagliflozin, dapagliflozin, and empagliflozin, have been evaluated for their use in weight loss, though their effectiveness has not demonstrated to reach that of the GLP-1 RAs.[25]

With literature reviews suggesting about 15% weight reduction at 1 year,[26,27] GLP-1 RAs may be a more effective alternative than bariatric surgery. Bariatric surgery induces a weight loss in the range of 5% to 16%, which can get as high as 30% of total body weight after 5 years.[28] However, such surgical interventions are fraught with complications and there is a long period of recovery, even with enhanced protocols.[24,29]

This may preclude surgical intervention of the spine for months to years, furthering patients’ disability from spinal pathology. GLP-1 RAs have yet to be evaluated in patients undergoing spine surgery. However, with their increased use, providers will not only see more patients who are actively on these medications, they may be formulating algorithms and plans to initiate GLP-1 RA therapy leading up to surgery. In many cases, busy spine surgeons may have a lead time of weeks to months before a patient is scheduled to undergo surgery. In obese patients with comorbidities, a multidisciplinary approach to patient care improves postsurgical outcomes. Therefore, is it feasible to have patients visit their internist and/or endocrinologist to initiate medical management of obesity with a GLP-1 RA to not only begin weight loss leading up to surgery, but also improve the overall long-term health status of each patient, improving outcomes.

Overall, obesity is a complex, multifactorial medical condition associated with various comorbidities that are linked to poorer outcomes following spine surgery. As rates of obesity continue to rise, there may be a role for medical management over surgical management of obesity, both leading up to and following spine surgery. With appropriate patient education and intervention, we may be able to care for this patient population more expeditiously without compromising outcomes following spine surgery.

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