September 2, 2020

The joint replacement-obesity connection

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Weight can be a barrier to joint replacement surgery. What to know about general health criteria related to the procedure.

Knee or hip pain caused by arthritis can be a barrier to doing things you enjoy. You may wonder whether you’re a candidate for joint replacement surgery, to get some function and mobility back. However, some health conditions, including obesity, can put you at risk for complications with healing after this type of surgery.

We asked Stephen Engstrom, MD, an adult reconstruction surgeon with Vanderbilt Orthopaedics, to explain what makes someone a candidate for joint replacement, and how those who don’t meet the criteria can work toward that goal.

When is surgery a consideration?

When it comes to arthritis pain, surgery should be considered as the last line of treatment. “Candidates for surgery are people who have severe arthritis in either the hip or the knee,” Engstrom said, “and who have tried other forms of conservative management — namely, steroid injections, physical therapy, anti-inflammatory medications and activity modification.” But overall health is also part of the big picture, and that’s where weight and medical conditions can come into play.

Why does BMI matter?

“Joint replacement in and of itself is a very successful operation,” Engstrom said. What he worries about are the complications that can arise after surgery. “We have found over years of research,” he explained, “that patients with a BMI over 40 have a substantially higher risk of infection, wound-healing problems, deep venous thrombosis and early loosening of the prosthesis, where the prosthesis actually starts to come loose from the bone.”

Why are health conditions a factor?

Before surgery, all health conditions should be medically managed as best as possible with either medications or lifestyle changes, Engstrom said. People who have high blood pressure, for example, should be on medication to keep them in a safe range. And people with diabetes should aim for a hemoglobin A1c below seven. Those who have a higher BMI should work toward getting it under 40 — or under 35 if possible.

Engstrom directs his patients toward resources that can help. “I don’t think it’s fair to look at patients and say, ‘You need to go lose 50 pounds. Come back and see me when you do,’” he explained. Vanderbilt Orthopaedics partners closely with the Vanderbilt Weight Loss Center for both medical weight loss and surgical weight loss.

“I let patients know that the thing that’s really going to help their joint pain the most is going to be the joint replacement, but the key is doing it as safely as possible.”

“With every patient who comes into my office with a BMI over 40 and other medical comorbidities that I think would make joint replacement unsafe,” Engstrom added, “I make sure they have a referral to the weight loss center and that they have a follow-up appointment with me. I let them know that the thing that’s really going to help their joint pain the most is going to be the joint replacement, but the key is doing it as safely as possible.”

Is a BMI of 40 or higher a strict barrier to surgery?

The risk of complications does go up substantially with a BMI over 40, Enstrom said. But that’s not always a deal-breaking number. Risk also depends on overall health. “If someone comes into my office and their only medical comorbidity is that they have a BMI of 41 or 42 — they don’t have diabetes, they’re a nonsmoker and they don’t have heart disease — then I think that places them in an acceptable risk category,” he explained.

A man paddles a canoe on a river.

If you are dealing with an injury, facing surgery or coping with chronic pain, Vanderbilt Orthopaedics offers a full spectrum of care. Our specialists work with you from evaluation and “prehab” through physical therapy and, if needed, surgery. We’ll help you get back to doing the things you love, pain-free. To make an appointment, call 615-936-7846.

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