Study Links Obesity with Longer Hospital Stays and Higher Total Knee Replacement Cost

Researchers tied obesity with longer hospital stays and expensive total knee replacements in patients, irrespective of whether or not the patient has any obesity related disease.

A new finding reported in the Journal of Bone and Joint Surgery claim that over 50 percent of the TKR patients have a body mass index within the obesity range i.e. more than 30kg/m2. This has been associated with an elevated risk for related comorbidities like diabetes, hypertension, osteoarthritis.

A few studies have linked the same to higher medical costs and extended hospital stays.  Despite this, most of them were inconclusive whether the higher related medical costs in obese TKR patients are directly due to higher BMI or related comorbidities.

"The higher costs associated with obesity are believed to be largely due to managing comorbid medical conditions linked to obesity, such as diabetes," said lead study author Hilal Maradit-Kremers, MD, an associate professor of epidemiology at Mayo Clinic in Rochester, Minn. And yet in this study, "even in the absence of comorbidities, patients with obesity had longer stays and higher hospital costs."

For this study, the researchers examined BMI, comorbidities, complications, outcomes and cost of care of nearly 8,129 patients who undertook 6,475 primary TKRs and 1,654 revision TKRs at a major medical center between 2000-2008.  The median age was 68. There were nearly 57 percent of the patients who underwent primary TKR and 53 percent of the women underwent revision TKR. The mean age was 31.6 kg/m2.

The researchers noticed that hypertension and diabetes were the most common patient comorbidities.  Patients with BMI values in the normal to overweight range had the lowest stay at hospital as well as the direst medical costs.  Every 5 unit increase in BMI beyond 30kg/m2 was tied to higher hospitalization cost for those undergoing TKR.  It was also associated with a mean hospital stay of .11 days longer for those undergoing primary TKR and .06 days longer those undergoing revision TKR.

"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, MD, an orthopaedic surgeon, also from Mayo Clinic.