Obesity and Joint Replacement Surgery
Discussions about obesity and joint replacement are becoming more commonplace. This is more so as the average patient weight continues to increase. This in turn contributes to more patients needing joint replacement surgery. Bad outcomes with these surgeries in certain weight classes have led to weight cut-offs for surgery. These cut-offs are often based on BMI (Body Mass Index). BMI is a measure of body fat based on height and weight. It is weight in kilograms divided by square of height in meters. A BMI of less than 18.5 is underweight. Normal weight is between 18.5 and 24.9. Overweight is between 25 and 29.9. Obese is 30 and higher. Morbidly obese is 40 and higher. Super obese is 50 and higher. Super-super obese is 60 and higher. The BMI cut-offs are usually for 18.5 and below; 40 and above.
Underweight status can correlate with malnutrition. Malnutrition is a significant risk factor for infection. An infection can doom a joint replacement and can result in consequences as dire as an amputation. Underweight status also raises concern for wound healing issues and intra-operative complications like fractures. As such, these patients would be advised to improve their nutritional status before surgery.
The reason for BMI cut-offs in the United States is more often due to morbid obesity as opposed to underweight status. Morbid obesity is a risk factor for higher complication rates. It can also result in malnutrition and its attendant complications. Other concerns include improper positioning of the joint replacement implants. This can result in instability and premature failure of the surgery. Morbid obesity can also result in fractures and soft tissue injuries during surgery. Morbid obesity is a risk factor for physical injury to the surgeon and assistant. As such, these surgeries can be physically impossible for some surgeons to perform after a certain BMI. It is for these reasons that some surgeons would insist on a BMI cut-off for certain patients.
Some patients would understand the risks of surgery in higher BMI patients but want to proceed with surgery. Surgeons won’t always agree. Experience, literature and the known severity of potential complications would prevent most surgeons from proceeding.
What do we do in these cases? Weight loss. Weight loss can be achieved through a combination of ways. Diet. Exercises. Lifestyle changes. Weight loss surgery. For patients already on the weight loss journey and doing well, we provide encouragement. For patients needing help, we refer to a nutritionist to help guide dietary changes and lifestyle changes. We would recommend regular exercising to also help with weight loss. Some patients would benefit from meeting with a weight loss surgeon. Important for surgeons to see is that these patients are willing to do the work to improve their outcomes following surgery. It might not be realistic to expect someone with a BMI of 52 to get to a BMI of 35 within a few weeks or months. However, if that person gets their BMI down to 45, it might show the surgeon the patient is committed to the weight loss journey. This can encourage the surgeon to consider joint replacement at a higher BMI threshold than they are most comfortable with.