Researchers from Hospital for Special Surgery found obese patients fare just as well as average weight patients after joint replacement surgery.

“Even though these patients are sicker and require more in terms of hospital resources, they do well,” lead author Susan M. Goodman, MD, a rheumatologist at Hospital for Special Surgery, said. “They do just as well as normal weight patients and that — in terms of pain and their ability to function after surgery, their decrease in limitations caused by their health status and their ability to lose weight — they have benefitted enormously.”

Worse outcomes

The common theory is that obese patients have worse outcomes after surgery than patients of average weight, Goodman said, which comes from researchers “lumping everyone with a body mass index more than 30” together. To remedy this, Goodman and colleagues including orthopedists Alejandro Gonzalez Della Valle, MD, and Mark Figgie, MD, used the center’s arthroplasty registry to stratify patients by body mass indexes (BMIs) into the following weight classes:

• average weight (857 patients);
• overweight (1,500 patients);
• obese class I (1,000 patients);
• obese class II (487 patients); and
• obese class III (291 patients).

Patients were compared for weight, WOMAC and self-reported SF-36 scores at baseline and 2-year follow-up.

Scores for pain and function improved in all of the BMI categories at 2-year follow-up. According to Goodman, patients in the highest obesity class initially showed worse preoperative pain and function scores, but at 2 years “they caught up.” Patients in class III had WOMAC scores of at least 80.

All of the patients, especially those in class III, felt they improved after surgery, but obese patients “still did not see themselves as functionally active and as functionally capable as normal weight patients,” she said.

Higher BMI, more weight loss

Compared with average weight patients, patients with the highest BMI lost the most weight at 2-year follow-up and patients who weighed the least lost the least weight. Patients with a BMI between 25 and 30 dropped 0.3 off their BMI, while 40% of patients in the class III group BMIs dropped an entire class.

After multivariate analysis, the researchers found race and education were linked with worse outcomes after joint replacement. Patients with the least education had higher BMIs and worse pain and function scores.

“Our bias has been that these patients do not do as well, and that did not turn out to be the case,” Goodman said. “They had more comorbidities. They went into this less healthy. They came into it almost a decade younger than people of normal weight, and they ended up significantly benefitting.” — by Renee Blisard Buddle