Obesity Not a Deterrent to Total Joint Replacement Surgery

Obese patients who underwent knee or hip total joint replacement (TJR) reported similar post-operative pain relief and improved function as normal-weight patients, according to a new study.

Researchers at the Geisinger Health System (Danville, PA, USA), the University of Massachusetts Medical School (UMMS; Worcester, USA), and other institutions collected data from a U.S. national sample of 2,040 patients who underwent total hip replacement (THR) and 2,964 who underwent total knee replacement (TKR) from May 2011 to March 2013. Pre- and post-operative function and pain were evaluated according to body mass index (BMI) status, defined as under or of normal weight, overweight, obese, severely obese, or morbidly obese.

The results revealed that while severely and morbidly obese patients had less postoperative functional gain than the other BMI groups following THR, and with greater obesity level associated with more pain at baseline, they also experienced greater postoperative pain relief six months after surgery, so that the average postoperative pain scores did not differ significantly among BMI groups. Similar results were shown for patients undergoing TKR. The study was published on July 19, 2017, in the Journal of Bone and Joint Surgery.

“It's challenging for a patient who is severely overweight and suffering in pain to exercise; often they just can't do it. Our evidence showed that severe morbidly obese patients can benefit almost equally as normal weight patients in pain relief and gains in physical function,” said lead author Wenjun Li, PhD, of UMMS. “Patients who can lose weight should, but we acknowledge many people can't, or it will take a long time during which their joints will worsen. If they can get the surgery earlier, once function is restored they can better address obesity.”

“Losing weight by making appropriate dietary changes and increasing the calories burned each day through water exercise programs and other aerobic, non-weight bearing activities is always appropriate to decrease the risk of complications for overweight patients,” said study co-author David Ayers, MD, of UMMS. “The debate will continue in the morbidly obese patients with BMI over 40, and the super obese with a BMI over 50, regarding what steps can and should be taken to lower the risks before these elective surgical procedures.”

BMI is a value defined as the body mass divided by the square of the body height, and is universally expressed in units of kg/m2. It was developed as an attempt to quantify the amount of tissue mass (muscle, fat, and bone) in an individual, and then categorize that person as underweight, normal weight, overweight, or obese based on that value. However, there is some debate about where on the BMI scale the dividing lines between categories should be placed, and recent studies claim that other measures, such as waist-to-height ratio (WHtR) and body fat, are better predictors.

Related Links:
Geisinger Health System
University of Massachusetts Medical School