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Pearls and pitfalls: Orthopaedics and obesity

By Annie Hayashi

Techniques, instrumentation, and surgical planning are “weighty” issues

Obese patients, particularly those who are morbidly obese, present a dilemma for many orthopaedic surgeons. From equipment and instrumentation to the surgical approach, orthopaedic surgeons have to make significant adjustments when treating the obese (body mass index [BMI] of 30 or more) (Table 1).

Fig. 1. A continuous positive airway pressure (CPAP) machine delivers air through a nasal mask while the patient is asleep, easing breathing. Courtesy of evo Medical Solutions, Adel, IA

For example, if your operating table has a weight restriction of 450 pounds, what do you do when the patient weighs 757 pounds? Regular-sized surgical instruments are frequently inadequate, and surgical approaches may have to be adjusted when treating such patients.

These “super-obese” patients often also have serious co-morbidities such as cardiovascular and pulmonary problems, sleep apnea and obstructive sleep apnea (OSA), and higher mortality rates—making them high-risk surgical candidates.

Obesity—High stress for heart and lungs
Before making an incision, the orthopaedic surgeon needs to know the possible complications that accompany obesity, according to Bruce G. French, MD, a trauma surgeon with Orthopaedic Trauma Reconstructive Surgery in Columbus, Ohio.

The hearts of obese patients are not normal. “The fatty tissue infiltrates the myocardial tissue, which can lead to arrhythmias, particularly bradycardia. The muscular tissue has decreased compliance,” says Dr. French.

“These patients have increased risk factors for coronary artery disease, including hypertension, diabetes, and abnormal lipid profiles. Their hearts are working double time to support their bodies,” he says.

The effects of obesity on the pulmonary system can cause shortness of breath and poor exercise tolerance. “When you tell your patients to exercise, they really can’t do it,” explains Dr. French. “The hyperlordosis and kyphosis associated with obesity prevents rib expansion so they can’t breathe.”

Sleep apnea, OSA serious complications
“Sleep apnea is an upper airway obstruction during sleep that results in apneic and hypopneic episodes. Once patients become apneic, they rapidly lose their already limited oxygen stores. In the obese population, this is a real problem” Dr. French explains.

OSA is defined by at least five apnea and hypopnea episodes per hour of sleep and is diagnosed in a sleep laboratory using polysomnography. Those who are obese are 6 times more likely to have OSA.

If the results of the polysomnography are positive, the patient can then be treated with a continuous positive airway pressure (CPAP) machine, which will prevent most of the apneas and hypopneas. CPAP machines function by splinting the upper airway open with air pressure that is delivered through a hose to a nasal mask—sealed over the patient’s nose and mouth (Fig. 1). The actual air pressure, also known as titrated pressure, is prescribed by a physician following a sleep study.

Dr. French recommends CPAP machines, as well as supplemental oxygen if it is needed, for all obese patients while they are in the hospital.

“If I have an obese trauma patient, I will discharge the patient to the sleep study lab for a polysomnography. If OSA is diagnosed, I can get insurance approval for an in-home CPAP machine pretty quickly,” he says.

Good OR plan a must
An operative plan that considers all the special needs of the morbidly obese patient is critical, according to Dr. French, who does not perform any significant outpatient surgical interventions on obese patients.

Because obese patients frequently exceed the weight capacity of the operating room (OR) table, he suggests placing two OR tables side by side, head-to-head or head-to-foot. This arrangement, however, makes it difficult to get a good lateral C-arm image with a fluoroscope.

A lateral position on the OR table is best for the obese patient; a prone position is the worst.

Dr. French also suggests allowing obese patients to position themselves on the table while they are awake so that the surgical staff won’t hurt their backs trying to move obese patients who are paralyzed by anesthesia.

Rhabdomyolysis can occur, particularly if the patient has been on his buttocks for a long time. Downside compartment syndrome has been reported as well as alopecia.

Anesthesia also has to be adapted to the special requirements of the very obese patient. “Often, anesthesiologists don’t want to intubate obese patients unless the patients are awake,” explains Dr. French. “The anesthesiologist will use fiber optic intubation or a regional anesthetic.”

The anesthesiologist should discuss which type of anesthesia will be used with the patient prior to the surgery. If a regional anesthetic is used, Dr. French suggests adding an extra hour to the operative time.

“Preoperative sedation should be given intravenously—not intramuscularly,” he notes. “If general anesthesia is used, my preference is to admit the patient to the intensive care (ICU) or the step-down unit following surgery.”

He contacts the unit staff to let them know what is needed. “I want to make sure that the patient doesn’t desaturate, doesn’t have any arrhythmias, remains oriented, and is able to take pain medications.”

The surgical instruments that are used on a routine basis may not be large enough for the morbidly obese patient. “We have a separate instrumentation set for some of our larger patients. It’s very helpful in reducing frustration and lowering operative time,” he says.

Once the surgery has been completed, Dr. French doesn’t use staples or sutures in the skin. “I put an adaptic dressing over the incision. The sponge should be just slightly less than the size of the adaptic to decrease wound complications.”

Wound complications are a major consideration for morbidly obese patients, according to George V. Russell Jr., MD. “If a patient is morbidly obese with a BMI of 40 or greater, the risk of a wound complication developing is 5 times greater than for normal-sized patients.”

Higher morbidity, increased mortality rates found
Obesity has been associated with higher morbidity and increased mortality rates.

In a large retrospective review of 1,153 trauma patients admitted to the ICU from 1998 to 2003, obese patients had more complications than those who were not obese (42 percent versus 32 percent; P=0.002).

Those who were obese had longer stays in the ICU, more days of mechanical ventilation, and showed a trend toward multi-system organ failure and acute respiratory distress syndrome. Obesity was also found to be an independent risk factor for mortality (odds ratio of 1.6; 95 percent confidence interval, range 1.0–2.3; P=0.03).

A plea for compassionate care
Dr. Russell has had extensive experience caring for the morbidly obese, in part because he practices in an area that has the highest incidence of obesity in the nation.

“Everybody knows that these patients are big,” he says. “They know it and we know it. But I would like to ask that we care for these patients with compassion as we work through these very difficult issues.”

Dr. Russell reported the following disclosures: Zimmer, Synthes, and Stryker. Dr. French did not have any disclosures to report.

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org

Fast Facts

  • From 1960 to 2000, the rate of obesity more than doubled in the United States—from 12.8 percent to 30 percent.
  • More than 60 percent of all Americans are now considered to be overweight or obese based on a BMI of 30 or more.

Obesity and Joint Replacement
Obesity substantially increases a patient’s chances of needing a joint replacement. The chances of having a knee replacement are 8 times higher for patients with a BMI greater than 30—and 18 times higher for patients with a BMI of 35 or more, according to Bas A. Masri, MD, FRCSC.

“The morbidly obese have higher complication rates, may have more pain after surgery, and have a higher rate of infection and a higher loosening or failure rate that would result in revision. The increase in obesity seems to have a greater effect on knee replacement patients compared to those requiring hip replacements,” says Dr. Masri (Table 2).

Once obese patients have a joint replacement, do they lose weight? Though many obese patients say they will lose weight following a joint replacement, the statistics do not support that claim.

According to one study, patients gained an average of 1.2 kilograms (kg) one year after joint replacement surgery.

“If the BMI was 25 to 30, the patients gained an average of 3.6 kg, which is much more than the weight of the implant. If the BMI was 30, there was no significant change,” says Dr. Masri.

Surgical outcomes can markedly improve if the patient loses weight prior to surgery, according to several studies.

“I have had personal experience caring for patients who have had bariatric surgery and the change is incredible,” he says. “It makes the joint replacement surgery more predictable and produces better outcomes.”

Dr. Masri will accept patients for joint replacement with BMIs up to 50. After that point, he refers them for bariatric surgery.

Dr. Masri’s institution receives financial support from Zimmer, Stryker, and DePuy.

AAOS Now
June 2009 Issue
http://www.aaos.org/news/aaosnow/jun09/clinical1.asp