Smoking Linked to Worse Outcomes in Joint Replacement
Hip and knee patients who smoked needed more revision surgery.
Two studies presented at the 2012 annual meeting of the American Academy of Orthopaedic Surgeon highlight the dangers that smoking poses to patients receiving total knee or hip implants.
The first study looked at more than 600 total knee replacements (in patients with an average age of 62), performed between 2005 and 2009 at the Center for Joint Preservation and Replacement at Sinai Hospital of Baltimore, and the Bonutti Clinic of Effingham, Illinois. Among the patients, approximately 115 were smokers.
The researchers found that the overall revision rate – meaning the number of surgeries that had to be redone – was 10 times higher for smokers compared with nonsmokers: 10 percent vs. 1 percent. Smokers also had a significantly higher rate of complications compared with non-smokers (21 percent vs. 12 percent), including blood clots, abnormal heartbeat, irregular heartbeat, urinary tract infection and kidney failure.
The second study used data from 535 hip replacements surgeries (in 500 patients) performed by Joint Implant Surgeons Inc., a private practice in New Albany, Ohio between 1999 and 2009. Of the surgeries, 160 were first time hip implants, and 375 were revision surgery. Among the patients, 17 percent were smokers, 29.5 percent past smokers, 49 percent nonsmokers and the smoking status of 4.5 percent of patients was unknown.
The results show there were 33 failures at an average of 18 months after surgery, which translates into a 6.2 percent failure rate. When broken down into smoking status, failure rates were 11 percent in smokers, 5.3 percent in previous smokers and 3.8 percent in nonsmokers.
The study looked at a specific type of hip surgery that reconstructed the cup-shaped cavity at the base of the hip bone – called the acetabulum – using porous metal. The idea is that bone grows into and around the porous implant, which secures it.
The researchers considered failures due to infection, an inability of the bone to grow into the porous metal or hip fractures as possibly related to smoking (non smoking-related failures included dislocation and implant breakage). When taking into account only smoking-related failures, the failure rate was 9 percent in smokers and 3.6 percent in nonsmokers.
Why this differences in failure rates between smokers and nonsmokers?
Nicotine constricts blood vessels, so wounds get less oxygen and healing nutrients, slowing and perhaps interfering with healing, says Adolph V. Lombardi, MD, president of Joint Implant Surgeons and lead author of the hip implant study. “Smokers may be getting as much as 25 percent less blood to the wound than nonsmokers. And bone healing is critical to this surgery, which requires the bone to grow into the implant,” he explains.
With less blood flow, the wound also receives fewer protective white blood cells, adds Dr. Lombardi. “So smokers are at increased risk of infection,” he says.
Dr. Lombardi speculates that nicotine’s restricting effect continues to some extent even after people quit, explaining why past smokers don’t do as well as people who have never smoked. Still, he found that patients who quit smoking before and during their treatments had less pain and better outcomes
Michael A. Mont, MD, one of the authors of the knee replacement study and director of the Center for Joint Preservation and Replacement, offers two other mechanisms by which smoking can interfere. He says that carbon monoxide also affect blood cells, decreasing oxygen delivery to tissues, so that the tissues are more apt to die.
“Smoking may also increase cause blood platelets to stick together more than usual, which can cause blood clots,” he adds.
People with arthritis – both osteoarthritis, or OA, and rheumatoid arthritis, or RA – are among those most likely to receive a knee or hip replacements. According to a 2008 study in the Archives of Internal Medicine, for instance, the prevalence of hip OA is about 7.5 percent and knee OA about 12.2 percent. The study found that hip replacement would be appropriate for almost 38 percent of the men and 53 percent of the women. And according to a 2008 study in Arthritis Care & Research, as the incidence of RA rises, so do hip and knee replacements.
For people with arthritis, whose health is already compromised and who may very well face replacement surgeries, smoking adds unnecessary and serious risks.
The link between smoking and worse outcomes in arthritis is well established. Previous studies, for instance, have linked smoking to new cases of rheumatoid arthritis as well as worse outcomes in people who have it. According to a Swedish study at Malmo University Hospital, presented at the 2009 annual meeting of the American College of Rheumatology, researchers found that smoking increased the risk of a person developing rheumatoid arthritis. And several studies have shown that people with RA who smoke tend not to respond as well to treatment. For instance, a 2011 study at Karolinska University Hospital in Sweden published in Arthritis & Rheumatism found that smokers were 50 percent less likely to respond well to treatment during early RA than nonsmokers.
Quitting’s not easy, but it’s worth it, says Dr. Lombardi. “The effect of nicotine may persist, but obviously it will [lessen] if you stop.”