What Is the Connection Between Obesity and Revisions?

A team of Australian researchers using the massive Australian Orthopaedic Association National Joint Replacement Registry designed a new study to put hard numbers to the relationship of obesity with all-cause revision and revision for infection, loosening, instability, and pain following total knee arthroplasty (TKA).

Their work, “A Prospective, Longitudinal Study of the Influence of Obesity on Total Knee Arthroplasty Revision Rate: Results from the Australian Orthopaedic Association National Joint Replacement Registry,” was published in the August 3, 2022, edition of The Journal of Bone and Joint Surgery.

Chris Wall, M.B.B.S., deputy director of the Department of Orthopaedics at Toowoomba Hospital in Queensland, Australia, was a co-author on this work and told OTW, “I am currently undertaking a Ph.D. investigating the influence of obesity on knee replacement outcomes in Australia. My first study identified that obesity significantly increases the risk of undergoing TKR, and at a younger age.”

Using the Australian Orthopaedic Association National Joint Replacement Registry, the team looked at 141,673 patients with recorded body mass index (BMI) who underwent primary TKA for osteoarthritis throughout Australia. Revision patients were defined by the research team as those patients who’d had their implant removed, replaced, or augmented by adding any implant component.

Of the 141,673 patients, 54.7% were female, with a mean age of 68.2 years. Of the total, 48% were class-I or II obese (BMI, 30.00 to 39.99 kg/m2), and 10.6% were class-III obese (BMI, ‡40.00 kg/m2).

Of the total number of patients in the study, 2,655 patients (1.9%) had had to return for a revision procedure during the study period.

Of that group, 1,055 (39.7%) returned for a revision because of infection, 392 (14.8%) returned because of implant loosening, 318 (12.0%) returned due to implant instability, 163 (6.1%) returned because of pain, and 727 (27.4%) returned for other reasons (e.g., patellofemoral pain, patellar erosion, arthrofibrosis, fracture, malalignment).

The all-cause cumulative percent revision rate at five years after surgery was 2.5% for non-obese patients, 2.9% for class-I and II obese patients, and 3.3% for class-III obese patients.

Dr. Wall told OTW, “In this, my second study, we determined that essentially, obesity increases the risk of all-cause revision and revision for infection following TKR, and morbid obesity also increases the risk of revision for implant loosening.”

“We know from the Australian Orthopaedic Association National Joint Replacement Registry Annual Report that younger patients have a higher risk of revision following TKR. With this fact in mind, and taking into account the findings of my two studies, we believe that Australia may face a growing burden of revision TKR in the future. A population-level approach to address the increasing prevalence of obesity is urgently needed to reduce the burden of obesity-related knee osteoarthritis, primary TKR, and revision TKR.”