SOURCE: AAOS

March 05, 2008 12:07 ET

One More Reason to Take That Weight Off!

Study Finds Obesity Limits Range of Motion and Causes Longer Recovery After Knee Surgery

SAN FRANCISCO, CA--(Marketwire - March 5, 2008) - Obesity limits a patient's range of motion (ROM), prolongs recovery and extends the need for physical therapy after total knee replacement surgery, according to a study presented today at the 75th Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS).

The study found that a patient's body mass index (BMI) had a direct correlation on the knee's range of motion and need for manipulation under anesthesia. BMI is a mathematical calculation of your height in relation to your weight. While fewer than 10 percent of patients with a BMI of less than 25 required manipulation to achieve greater flexibility and break up scar tissue, almost 20 percent of patients with a BMI of 25 to 30 required manipulation.

According to Geoffrey Westrich, MD, lead author of the study and an associate professor of orthopaedic surgery at Hospital for Special Surgery in New York City, "For anyone considering knee replacement surgery, recovery time is always an important consideration. Patients often ask me if their pain is going to be relieved and if they will have better range of motion. Our findings will help set more realistic expectations for heavy patients. They need to be counseled that their weight will likely impede their recovery."

The study compared data from 309 patients (400 knee replacements) who underwent total knee replacement surgery at Hospital for Special Surgery. Researchers evaluated the effect of BMI on range of motion and the need for manipulation under anesthesia. Patients were divided into groups according to their BMI, ranging from less than 25 to greater than 29.9.

Other significant findings in the study found that:

-- The greater a patient's BMI, the less range of motion they can
   expect after knee surgery
-- Age was not a predictor for range of motion
-- Gender was a predictor for range of motion and the need for manipulation
-- Regardless of BMI:
    - Men had a 4.6-degree higher range of motion than women
    - Less than 10 percent of men needed manipulation six weeks after
      surgery compared to 18.5 percent for women

"Our study reinforces the drain that obesity is having on the health-care system," Dr. Westrich said. "The obesity epidemic is causing health-care expenditures to grow at a rapid rate. Insurance companies, Medicare, hospital administrators, and patients need to understand that obesity will likely cause different patient outcomes, including more complications that may require further surgical interventions." Dr. Westrich concludes that "setting realistic expectations prior to surgery is paramount to patient care."

Most patients who undergo total knee replacement are between 60 and 80 years old, but orthopaedic surgeons evaluate patients individually. Recommendations for surgery are based on a patient's pain and disability, not age. Total knee replacements have been performed successfully at all ages, from the young teenager with juvenile arthritis to the elderly patient with degenerative arthritis. Surgeons performed more than 533,000 knee replacements in 2005.

Disclosure: Dr. Westrich received no compensation for this study.

Abstract P188

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