Over 50% TKR Patients Obese – New JBJS Study

Obesity is associated with longer hospital stays and higher costs in total knee replacement (TKR) patients, according to a new study published in the Journal of Bone and Joint Surgery. The increases hold true regardless of whether the patient has an obesity-related disease or condition.

The study investigators found that more than half of TKR patients have a body mass index (BMI) that is within the obesity range—a range that is linked to a higher risk for related comorbidities such as diabetes, hypertension and osteoarthritis. Medical Press, which reported the study, indicated that research is inconclusive as to whether the higher medical costs in the cases of obese TKR patients are due directly to their higher BMI or to their related comorbidities.

In the study, researchers reviewed the BMI, comorbidities, complications, outcomes and cost of care of 8, 129 patients who had undergone 6, 475 primary TKRs and 1, 654 revision TKRs at a major medical center between January 1, 2000 and September 30, 2008. The median patient age was 68. Fifty-seven percent of the patients who underwent primary TKR and 53% who underwent revision TKR were female. The mean patient BMI for the study subjects was 31.6 kg/m²—slightly higher than the range of 30kg/m2, which is the level defined for obesity.

The investigators found that the most common patient comorbidities were hypertension and diabetes. The length of stay and medical costs were lowest for patients with BMI values in the normal to overweight range. Every 5-unit increase in BMI beyond 30 kg/m² was associated with higher hospitalization costs and every 5-unit increase in BMI beyond 30 kg/m² was associated with a mean hospital stay that was 0.11 days longer for patients undergoing primary TKR and 0.06 days longer for patients undergoing revision TKR.

“The higher costs associated with obesity are largely due to managing comorbid medical conditions linked to obesity, such as diabetes, ” said lead study author Hilal Maradit-Kremers, M.D., an associate professor of epidemiology at Mayo Clinic in Rochester, Minnesota. “Even in the absence of comorbidities, patients with obesity had longer stays and higher hospital costs, ” he said.

“The bottom line is that obesity is increasingly common among patients undergoing joint replacement, which creates a myriad of technical and medical challenges, and likely contributes to the financial burden of the surgery, ” said senior author David G. Lewallen, M.D., an orthopedic surgeon at Mayo Clinic.