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 having total knee or hip replacement.
One study looked at more than 600 total knee replacements 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 other study used data from 535 hip replacements surgeries performed between 1999 and 2009 by Joint Implant Surgeons Inc., a private practice in New Albany, Ohio. 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.
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.
This study looked at a specific type of hip surgery that reconstructed the cavity at the base of the hip bone 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. They noted that smoking-related failure rates were 9 percent in smokers and 3.6 percent in nonsmokers.
Why the differences? 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, a co-author 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.
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.”
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