After total knee replacement surgery, obesity limits a patient’s range of motion, makes the recovery period longer and calls for extended physical therapy, according to a recent study. A patient’s body mass index (BMI)—a correlation between height and weight—has a direct relationship on the knee’s range of motion and need for manipulation under anesthesia.
Close to 20% of patients with a BMI of 25 to 30 needed manipulation for improved flexibility and to break up scar tissue, while patients with a BMI of less than 25 needed the manipulation. Said 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". Heavy patients, he continued, need to be advised that their weight will probably slow their recovery.
Data from 309 patients (400 knee replacements) who underwent the procedure at Hospital for Special Surgery was evaluated for the effect of BMI on range of motion and the need for manipulation under anesthesia. Patients with BMI from less than 25 to more than 29.9 were divided into groups: major findings from the study were as follows:
- 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.". Surgeons performed more than 533,000 knee replacements in 2005.
The study was presented at the 75th Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS) in March, 2008.