September 2007
The most severe epidemic in America today does not involve a virus or bacteria, but is the epidemic of obesity. If you have been on an airplane in the past year you know what I am talking about, the person in the middle row is broader than the seat was designed and your room is being taken up by that person.
Obesity is defined medically by looking at what is called your body-mass-index (BMI). The marathon runner is a18-22 BMI. Most people of average BMI are 22-28. Obese is considered a BMI of 30- 39, morbidly obese 40-49 BMI, and greater than 50 BMI is something else. By the numbers, the situation is this; as of 2000, 30.5% of the American public was obese, an increase of 110% in 25yrs. In a registry of patients receiving total joint replacements, for 1990-1999, 47% of the patients were obese, for 2000-2006 that number jumped to 55%, and in my practice 65% of the patients that I see who need total knee replacement surgery are obese. Obesity represents an annual national health care cost of 117 billion dollars, about equal to smoking.
The effect of obesity on patients who require a total knee replacement is significant. They put a greater demand of the medical team; require more resources, longer operating time and length of time in the hospital. Their wounds heal slower and have a greater frequency of wound infections. They are more likely to develop pneumonia and phlebitis. Lastly, their prosthesis does not last as long and many need to be re-operated in 5-7 years for loosing of the ligaments about the knee.
The issue is one of body mass. The more the body mass the more stress is placed on the ligaments that hold the knee and the prosthesis together and the effect is a multiplier, or geometric, effect. Normally a total knee is expected to last 15 – 20 years with a very few failing in less than that time. In the obese total knee patients I am finding that 10-20% of these patients are requiring a second, or revision, operation 5-7 years after the original operation.
You ask, what is the solution? Obviously loose weight, but that is not easy. Most patients that I see are caught in the dilemma of already having an arthritic knee and being obese and unable to exercise to loose weight. My hope and effort is directed at providing the patient with a total knee and the ability to then exercise and loose their weight. The issue is what kind of prosthesis? I have been using a “stronger” prosthesis that will carry the patients increased weight, protect the ligaments and “share the load” more effectively. It is still early and we are not sure how much we will improve the failure rate, but feel confident that patients will do better than with the use of a “standard” total knee prosthesis.
Having said the fore going, I feel that if an obese patient has an arthritic knee and is in need surgery to replace it, then they should look for a physician and hospital that performs a high volume of total knees on the obese patient. In addition, they should be able to take care of their patients “holistically”, have access to bariatric care, and have a strong interest and significant experience in care of the obese patient.
Richard W. Cohen M.D. is a physician with Resurgens Orthopaedics and focuses on Arthritic and Reconstructive surgery of the hip and knee. Dr. Cohen serves as Co-Chair of WellStar Total Joint Center and Chair of the WellStar Ethics Committee.
