American Academy of Orthopaedic Surgeons Annual Meeting

American Academy of Orthopaedic Surgeons Annual Meeting

Issue: June 2011
June 01, 2011
2 min read

Study shows increased operative times for performing total knee replacement in overweight patients

Issue: June 2011
You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact

Total knee arthroplasty takes more time to conduct in overweight and obese patients than in patients of normal weight, according to results of a recently presented study.

According to the study authors, the findings may have implications for hospital staff in terms of scheduling surgeries, operating room (OR) use and personnel staffing. The research also raises the question of whether surgeons should be reimbursed for knee replacement procedures based on operative time.

Geoffrey H. Westrich, MD, shared his team’s findings at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons.

Westrich noted that obesity is “clearly an epidemic in the United States,” with 71% of patients older than 60 years being classified as overweight or obese. Complications of obesity, such as a higher risk of osteoarthritis, can lead to an increase in the number of knee replacements performed in these patients.

Measuring obesity

For their study, Westrich and colleagues investigated the relationship between obesity and the time required to complete standard tasks in the OR during unilateral total knee arthroplasty (TKA). They hypothesized that a positive correlation existed between an increase in body mass index (BMI) and OR use.

Westrich and colleagues retrospectively reviewed 454 consecutive primary TKAs performed by one surgeon between 2005 and 2009 using a posterior-stabilized implant. They used the World Health Organization’s BMI classes to group patients as normal weight (BMI of 18.5 to 25), overweight (BMI of 25 to 30), obese class I (BMI of 30 to 35), obese class II (BMI of 35 to 40) and obese class III (BMI greater than 40).

Westrich and his team used five standard intraoperative time measurements — total room time, anesthesia induction time, tourniquet time, closing time and surgery time — and compared these measurements across BMI groups.

The investigators observed a progressive increase in OR time as the BMI category increased. They also found statistically significant differences between the normal weight group and all obesity categories.

Link between BMI, obesity

When comparing the normal weight group with obese class III patients, the team discovered that the obese group showed a 19% increase in total room time, a 22% increase in surgery time, 15% increase in tourniquet time and a nearly 30% increase in closure time.

“Clearly, we found that OR time is directly related to the BMI category,” Westrich said. “There was an over 20% average increase in surgery time from normal to obese class III.” The actual surgical steps and duration of the surgery were most affected by a higher BMI, he said.

“The prevalence of obesity is increasing, and our knee replacement population is definitely increasing in this category,” Westrich said. “More knee replacements in obese patients mean more time-consuming knee replacements to be performed. We also know that hospital resources are greatly increased when dealing with obesity … hospitals performing knee replacements on obese patients must plan for the future and should potentially be met with greater reimbursement.” – by Robert Press

  • Westrich GH, Gadinsky NE, Manuel JB, Lyman S. The increased use of operating time in obese patients during primary total knee arthroplasty. Paper #595. Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19. San Diego.

  • Geoffrey H. Westrich, MD, can be reached at Hospital for Special Surgery, 535 E 70th St., New York, NY 10021-4898; 212-606-1000; email:
  • Disclosure: Westrich receives royalties from Exactech, Inc., is a paid consultant for DJ Orthopaedics, Exactech, Inc. and Stryker, and receives research or institutional support from DJ Orthopaedics, Exactech, Inc. and Stryker.