The Risks of Early Knee Replacement Surgery

As more and more Americans choose to have total knee replacement surgery (TKR) at increasingly younger ages, the number of revision surgeries — procedures to correct a failed joint replacement — is also soaring.

According to a study of more than 2 million knee replacement patients presented at the 2014 American Academy of Orthopaedic Surgeons (AAOS) meeting, there was a:

• 120% increase in knee replacements over a 10-year period.  
• 89% increase in knee replacements among those aged 65 to 84. 
• 188% increase in knee replacements for 45- to 64-year-olds. 

Some revision surgeries are relatively minor — for instance, when one component of the implant is exchanged for another. But many entail removing and replacing the entire implant device, the ends of which are affixed to the thigh and shin bones. Revisions are long and complex, require special surgical skills and are rarely as successful as the first operation at restoring function and range of motion.

Studies have found that 85% of knees last 20 years, and the AAOS estimates 10% of patients will need a revision at some point. The younger you are when you have the surgery and the longer you live, the more likely it is you will need revision surgery.

“We had some theoretical concerns about how young is too young,” says lead study author Jacob Drew, MD, of the Medical University of South Carolina in Charleston. The study’s findings seemed to support his concerns: The number of revision surgeries increased 133% during the study period, particularly among younger patients.

“It appears that revision rates are growing in a younger age group, but the value is to focus on understanding why these patients are at increased risk,” says William Robb, MD, director of the Illinois Bone and Joint Institute, a Chicago-area orthopedic practice.

Researchers at the University of California, San Francisco (UCSF) evaluated the reasons for revision surgery in nearly 302,000 procedures performed over a five-year period. The most frequent causes of revisions were joint infections and implant loosening (when the bond between implant and bone fails). Far less common were fractures in the bones around the implant and osteolysis (when debris from the implant damages or destroys surrounding tissue).

Although improvements in implants and surgical techniques have reduced rates of implant loosening, infection rates haven’t improved, in part due to changing patient characteristics. “We know that smoking, diabetes, obesity and [poor] nutrition increase the risk of infection. In fact, the risk of all complications increases exponentially in patients with a body mass index [BMI] of 40, and even those with a BMI of 30 to 40 are at increased risk,” says lead study author Kevin Bozic, MD, a professor of orthopedic surgery and vice chair of the department of orthopedic surgery at UCSF.

Younger knee replacement candidates are more likely to be obese and have health issues than those over 65, says David Ayers, MD, chair of the department of orthopedics and physical rehabilitation at the University of Massachusetts Medical School. “People assume that most knee replacement patients are young, active baby boomers who have damaged their knees through sports and other activities. But when we look at the representative set of patients age 45 to 64, they aren’t like that.” 

Other studies have found that although replacement surgeries are more common among women, men were more likely need revision surgery or have such complications as infection, joint failure or heart attack. 

For example, in a 2013 study published in Arthritis Care & Research, which examined data from about 18,000 knee replacement surgeries during a one-year period (the average age of men and women was 69), men had a:

• 48% higher risk of dying from any cause after one year.  
• 31% higher risk of wound infection.  
• 25% higher likelihood to be readmitted to the hospital within 30 days.  
• 20% higher rate of revision surgeries within the first five years than women.

The authors suggest men may have a higher five-year revision rate because of differences in knee biomechanics and a higher level of physical activity. And the increased risk of mortality, they write, “likely reflects the gender-specific cardiovascular disease mortality advantage for women.”  

The rising numbers of younger adults interested in a total knee replacement creates a dilemma for doctors. “If a patient has debilitating pain and loss of function at age 47, do we ask him to wait as long as possible before undergoing total knee replacement so the need for revision is less likely? Or do we perform the procedure, relieve the pain and get the person back in the workforce, knowing that he may need a revision 20 years down the road?” asks Dr. Drew. "That question is very difficult to answer.”

Instead of rushing into surgery, younger people can try other treatments to manage knee pain – including corticosteroid injections and over-the-counter pain relievers. Losing weight can also help take pressure off damaged joints and improve outcomes in people who do undergo knee replacement surgery.

Once the decision to have surgery has been made, surgeons and patients need to work together to ensure the best outcome.