Mar. 5, 2009 Common sense suggests that extra body weight severely stresses bones and joints. But until the findings of a new Mayo Clinic study were presented February 26, no one had reported how this higher, unprecedented level of obesity in the U.S. affects total hip replacements, implanted to restore mobility and relieve the chronic pain of hip degeneration.
Mayo researchers found that obesity has a significant effect. "While technically feasible, there is a much higher complication rate -- more than 50 percent -- in hip replacement patients regarded as superobese," explains Mayo Clinic orthopedic surgeon David Lewallen, M.D., the senior researcher. "This suggests we must do much more to help these patients recover their health by helping them lose weight when possible prior to implant surgery."
Body Mass Index (BMI) is the measurement of choice for many physicians studying obesity. BMI uses a mathematical formula that takes into account a person's height and weight.
In this Mayo study, patients diagnosed as superobese had a BMI greater than 50. Generally, a BMI of 30 indicates obesity. A person 6-feet tall with a BMI of 30 would weigh about 225 pounds. A person that same height with a BMI of 50 would weigh 369 pounds.
In the study, 43 patients categorized as superobese underwent total hip arthroplasty from 1996 to 2006. This surgical procedure replaces a worn, fractured or damaged hip joint with a prosthetic implant. The patients had a BMI ranging from 50 to 77, and a mean age of 56.
Mayo followed them an average of three years to determine outcomes. Results showed:
- More than half (56.5 percent) experienced either surgical or medical complications, including prolonged wound drainage.
- Five of the 43 patients required a total of 15 re-operations to correct problems such as recurring dislocation of the implant, chronic infection and new bone fractures around the device.
Mayo Clinic orthopedic surgeons presented this research at the annual meeting of the American Academy of Orthopedic Surgeons (AAOS) in Las Vegas, Feb. 25-March 1.
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