Tobacco Worse Than Obesity in Revision TKA

New data from a University of Missouri School of Medicine study provides evidence that tobacco use by patients creates more adverse event risk than obesity. The study, “Tobacco Use Is Associated with More Severe Adverse Outcomes Than Morbid Obesity after Aseptic Revision TKA,” was originally published in the Journal of Knee Surgery.

Study co-author James Keeney M.D. and his team looked at 239 first-time total knee replacement procedures performed over seven years and then collected data for patients who did not have one of three modifiable risk factors—morbid obesity, diabetes, and tobacco use history. They then compared the outcome data to those of 270 first-time knee replacement patients with one modifiable risk factor (20% with tobacco use history, 12% with morbid obesity and 12% with diabetes).

“Knee replacements help hundreds of thousands of patients each year to relieve pain and improve function,” Dr. Keeney, associate professor of orthopaedic surgery at MU Health Care, told OTW. “Increasing success with knee replacement surgery over the past four decades has resulted in enthusiasm for the procedure and has resulted in surgeons extending knee replacement surgery for an increasing number of younger patients.”

“Published studies have indicated that the largest growing group of patients undergoing knee replacement surgery is less than 55 years old. We were interested in looking in looking at the results of knee replacement surgery in this population because little has been reported on the outcomes of revision knee replacement in younger patients. Those studies have generally not compared results to a traditional joint replacement aged patient group (traditional age is 60-75 years).”

The researchers found that patients who smoked tobacco cigarettes had a nearly 10% increased rate of reoperation, a 10% increased rate of surgery within two years and a 3.2% higher rate of above-knee amputation as compared to the healthy patient population.

“There are a variety of factors that may contribute to younger patients having earlier repeat revision operations,” said Dr. Keeney to OTW. “These may include higher expectations for knee replacement performance, higher demands placed on the knee replacement, or the presence of mechanical symptoms that they consider undesirable. A higher rate of poor medical health in younger patients may also play a role. One factor that we identified in our younger aged patients was a higher rate of tobacco use (smoking). Smoking places patients at an increased risk of wound healing complications or infection after knee replacement surgery. Another factor can be related to being overweight.”

“Patients who are morbidly obese have a higher risk of injury to the tendons that course over the front of the knee—called the extensor mechanism. A third factor can be related to a healthier healing response and faster development of scar tissue after surgery. Younger patients also have more robust drive for tissue healing after surgery. This combined with increased sensitivity to pain can contribute to them developing stiffness after knee replacement surgery. All of these factors were identified in our study as common reasons for reoperation after revision TKA [total knee arthroplasty] in younger patients compared with patients who were a decade or two older when they underwent their revision surgeries.”

“The study has helped me to reflect on how we provide care to our patients. I was surprised to see the high number of patients that we have treated who had potentially modifiable risk factors. While we have not always asked our patients to stop smoking before surgery, our study has helped us to recognize the importance of this. It is probably more important for patients undergoing revision knee replacement than it is for patients undergoing a first-time knee replacement surgery.”