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).

Obesity—High stress for heart and lungs
Before making an incision, the orthopaedic surgeon needs to know the possible complications that accompany obesity.

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.

Obese 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.

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. 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.

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. The actual air pressure, also known as titrated pressure, is prescribed by a physician following a sleep study.

Orthopedic surgeons may recommend CPAP machines, as well as supplemental oxygen if it is needed, for all obese patients while they are in the hospital.

Wound complications are a major consideration for morbidly obese patients. 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).

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.

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.

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.

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

Some patients have had bariatric surgery and the change is incredible. It makes the joint replacement surgery more predictable and produces better outcomes.

Some orthopedic surgeons will accept patients for joint replacement with BMIs up to 50. After that point, they are referred for bariatric surgery.

Thanks,

JTM, MD

http://www.aaos.org/news/aaosnow/jun09/clinical1.asp

AAOS Now
June 2009 Issue