Obesity is a big problem in the United States, where two thirds of the population is either overweight (body mass index [BMI] of 25 to 29.9) or obese (BMI of 30 or higher). That presents an issue—not only for orthopaedists and other medical specialists—but also for policymakers trying to find ways to cut healthcare costs.

At the AAOS Now forum, “Obesity, Orthopaedics, and Outcomes,” held prior to the 2013 AAOS Annual Meeting in Chicago, S. Terry Canale, MD, AAOS Now editor-in-chief, outlined the immensity of the problem. In his own office, for example, during a 2-month period (Jan. 2–March 2, 2013), 84 of 517 patients (16 percent) met the criteria for obesity; nearly 25 percent of those patients had type III obesity (BMI of 40 or higher).

“Not only do obese patients have poorer outcomes, the expense of treating them is much higher than that for nonobese patients,” explained Dr. Canale. The forum, he continued, was designed to provide information on complications and comorbidities, as well as to examine effective methods of weight-loss assistance.

Scope of the problem
“From 1960 to 2000, the rate of obesity more than doubled in the United States,” said Frank B. Kelly, MD, AAOS Now editorial board member and forum moderator. “By 2010, more than 72 million U.S. adults were obese, and no state had an obesity rate of less than 20 percent.”

Dr. Kelly explained that the problem isn’t limited to adults. Nearly one in three children is overweight or obese.

The impact of obesity on healthcare spending is significant. “Obesity results in an additional $215 billion in increased medical expenditures each year,” said Dr. Kelly. “By 2030, healthcare costs attributable to overweight and obesity are predicted to account for 16 percent to 18 percent of total U.S. healthcare costs.”

In addition, evidence is mounting that obesity has detrimental effects on the outcomes of the procedures performed and the conditions treated by orthopaedic surgeons.

Diagnosing obesity
According to Elena Losina, PhD, associate professor of orthopaedic surgery at Harvard Medical School, Brigham and Women’s Hospital, Boston, the impact of obesity on life expectancy is significant, particularly for individuals with sedentary lifestyles. “Obesity and inactivity combined can take as many as 7 years off life expectancy,” she said.

When it comes to the reasons for obesity, Dr. Losina noted several contributing factors, including poor nutrition (a high-fat diet, poor nutritional knowledge, overeating, and eating out), physical inactivity, psychological problems, lack of willpower, and metabolic or endocrine disorders. Weight reduction is best accomplished through a multidisciplinary weight loss program consisting of diet, exercise, and behavior modification.

“Because each additional kilogram (kg) of body mass increases the compressive load over the knee by roughly 4 kg, even modest weight reduction is capable of achieving sizable decreases in the compressive stress over the knee,” she explained.

Robert F. Kushner, MD, MS, clinical director of the Northwestern Comprehensive Center on Obesity and professor of medicine, division of general internal medicine, Northwestern University Feinberg School of Medicine, pointed out that obesity is associated with more than 60 medical conditions, although the incidence and prevalence vary by sex, age, and BMI class.

Among the conditions he reviewed were the following:

• Cardiorespiratory fitness
• Atherosclerotic diseases, including coronary artery disease and peripheral vascular disease
• Type 2 diabetes
• Sleep apnea
• Hypertension
• Dyslipidemia

The impact of these associated comorbidities on surgical outcomes was discussed by William M. Mihalko, MD, PhD, professor and JR Hyde Chair at the Campbell Clinic department of orthopaedics and biomedical engineering at the University of Tennessee. According to Dr. Mihalko, increases in BMI affect fasting blood glucose levels, which, in turn, are associated with the risk of surgical site infections.

In one study, for example, 90 of 318 diabetic patients (28.3 percent) developed postoperative complications after orthopaedic surgery. Blood sugar levels (HbA[1c]) lower than 7 percent were significantly associated with decreased infectious complications. Another study found that a hyperglycemic index of 1.76 or higher was an independent risk factor for surgical site infections.

“Ideally, preoperative blood sugar should be controlled prior to elective surgery,” said Dr. Mihalko.

In patients with heart disease, the biggest issue is how the stress of surgery affects heart function. “We need to make sure these patients have enough reserve to undergo the procedure,” said Dr. Mihalko, who pointed out that obese patients undergoing total hip arthroplasty (THA) may have higher mortality rates, and obese patients undergoing bilateral total knee arthroplasty (TKA) may have higher rates of coronary events.

Obesity is also an independent risk factor for deep venous thrombosis (DVT) and pulmonary embolism (PE) in foot and ankle trauma, although the incidences of DVT and PE are quite low (0.28 percent and 0.21 percent, respectively). “Due to the low incidence of DVT and PE, routine pharmacologic thromboprophylaxis might be contraindicated in foot and ankle trauma,” said Dr. Mihalko. He cautioned, however, that “individualized assessment of the risk factors associated with DVT and PE is important.”

Sleep apnea is another issue that must be considered. Recent studies have shown that the following factors increase a patient’s risk of having moderate-to-severe obstructive sleep apnea:

• BMI of 28 or greater
• Age 50 years or older
• Neck circumference of 16 inches (for a female) or 17 inches (for a male)
• Male sex

Dr. Mihalko noted that obese patients who undergo orthopaedic procedures in an ambulatory surgery setting have higher rates of perioperative complications than do normal-weight patients. “Even when regional anesthesia is used, obese patients with sleep apnea have higher complication rates after orthopaedic procedures,” he said.

Although surgical interventions such as gastric bypass or bariatric surgery may be helpful, educating patients on the dangers of obesity is key, said Dr. Mihalko. “Exercise habits are difficult to change once arthritis develops,” he noted, “so the key is to effect changes in both eating and exercise habits early.”

Obesity and anesthesia
According to R. Dean Nava Jr, MD, instructor in anesthesiology at the Northwestern University Feinberg School of Medicine, anatomic and functional differences in airways for obese patients present problems during surgery. Obese patients tend to have short, thick necks; thick submental fad pads; limited movement in the atlantoaxial joint and cervical spine; suprasternal, presternal, and posterior cervical fat; and excessive tissue folds in the mouth and pharynx.

In addition, functional differences between obese patients and normal-weight patients include the following:

• Decreased residual volume
• Worsened ventilation-perfusion mismatch
• Increased atelectasis
• Decreased functional residual capacity

These issues present problems during surgery, particularly for the anesthesiologist, noted Dr. Nava. “Both mask ventilation and intubation are difficult,” he said, “and there is little room for error.” He reviewed various options, including regional anesthesia techniques, neuraxial anesthesia, and awake intubation, as well as strategies for postoperative analgesia, such as opioids, NSAIDs, regional techniques, tramadol hydrochloride, and neuraxial analgesics.

Intraoperative management
Kenneth A. Krackow, MD, professor and vice-chairman of the department of orthopaedics at the University of Buffalo School of Medicine, pointed out that orthopaedic surgeons need to work with overweight and obese patients before agreeing to perform joint replacement surgery—even suggesting bariatric surgery, with the joint replacement as “the carrot on the stick.” He noted that BMI is not a picture of obesity per se.

“To most surgeons, obesity is appreciated in the overall proportion of extra fat,” he said. He provided the following “technical tips” for TKA in the obese patient:

• Use hip-sized retractors; Penrose drains can be used to hold them in place.
• A Muller lateral knee incision may have advantages over a straight mid-line incision because the curve lessens tension along the edges, and the skin and subcutaneous fat can be moved medially, to allow the patella to move laterally more easily.
• A leg holder or elastic bandage (wrapped around the ankle and ends tied at the thigh) can be used to hold the knee in flexion

A report on the forum’s findings with regard to specific patient populations (pediatric, spine, trauma, athletes, and foot and ankle) and the impact of value measurements on orthopaedic surgery for the obese will appear in the May issue of AAOS Now. For a copy of the agenda book, including selected abstracts on obesity in orthopaedic surgery, email aaoscomm@aaos.org

Mary Ann Porucznik is managing editor of AAOS Now. She can be reached at porucznik@aaos.org