Mortality Rates After Total Hip Replacement Drop
Researchers say four factors explain the decrease.
Deaths from hip replacement surgery were almost cut in half during an eight-year period in England and Wales, according to a new study published recently in The Lancet. The study authors report the drop is mainly due to four factors – the way the surgery is performed, choice of anesthesia and two methods of preventing blood clots – all of which are used in the United States, too.
Researchers stress that death from hip replacement surgery is rare. But they say this is an important area of study given the number of total hip replacements done each year. There were more than 300,000 surgeries in the U.S. alone, according to a 2010 survey cited by the Centers for Disease Control and Prevention (CDC). And the number is expected to rise sharply in the coming years.
The findings are based on data from more than 400,000 first-time hip replacements to treat osteoarthritis, performed between April 2003 and December 2011. The information comes from the National Joint Registry for England and Wales, which has collected information on all total hip replacements done there since 2003.
The researchers found that, overall, 1,743 patients – or 0.4 percent – died within 90 days of surgery. But during the course of the eight-year study period, the mortality rate dropped by almost half, from 0.56 percent in 2003 to 0.29 percent in 2011. When the researchers analyzed the data, they found the drop was linked to “four simple clinical management strategies.”
One of those is the “posterior surgical approach,” which means the surgeon accesses the hip through the buttocks muscles instead of coming in from the side or front. Senior study author Ashley W. Blom, MD, says this method preserves more muscle and has clear advantages from a mortality standpoint.
“The posterior approach causes less bleeding and less muscle damage so patients walk better,” explains Dr. Blom, a professor in the Musculoskeletal Research Unit in the School of Clinical Sciences at the University of Bristol in England.
While the posterior approach is the most conventional, there are other surgical avenues. The anterior approach, which involves going through the front of the leg or thigh, is newer and growing in popularity because it is supposed to be less invasive. Surgeons don’t cut through muscles, which some believe shortens recovery time. Other possibilities include the lateral approach through the side of the hip, or a combination of approaches. There is no conclusive research showing one approach is better than another.
Hip and knee surgeon Matthias Bostrom, MD, a professor of orthopaedic surgery at Hospital for Special Surgery, in New York City, says the posterior surgical approach is the standard approach used in the majority of hip replacements in the U.S.
The other three other factors linked to the drop in mortality rates include the use of spinal anesthesia (alone or with another type of anesthesia) and the use of blood clot prevention methods – both “mechanical” (compression devices that squeeze legs to encourage blood flow) and “chemical” (the use of blood thinners, in this case heparin, with or without aspirin). Preventing blood clots in the legs is very important because clots can travel to the heart or lungs and cause death.
Dr. Blom explains that spinal anesthetics give better pain relief so patients less frequently need opiates, like morphine, after surgery. This is important, he says, because opiates can cause respiratory depression, vomiting and confusion.
These four strategies are not without risks or challenges. In an accompanying commentary, authors point out the posterior approach can be associated with a higher rate of dislocation, which could require revision surgery. Spinal anesthesia has its own side effects and requires highly trained anesthesiologists, which could be impractical. And there is no consensus on the best way to prevent blood clots. The commentary commends the study but notes that “treatment of all patients with the approach proposed in this report might be impractical.”
Among the study’s other findings: The type of implant used for the hip replacement didn’t appear to impact mortality; sicker patients (including those with severe kidney or liver disease, metastatic cancer and congestive heart failure) have a higher risk of mortality, as do older patients; and overweight patients appear to have a lower mortality risk. The authors caution that this last observation could be skewed because they didn’t have BMI data for nearly 60 percent of study participants.
Dr. Bostrom says this study’s findings offer helpful clues to U.S. patients about topics they should discuss with their surgeons before undergoing a hip replacement. “You want the right anesthetic. You want to make sure they are doing something to prevent blood clots, and the time-honored way of approaching the hip through the posterior approach works very well,” he explains.
And though this study is based on data from England and Wales, Dr. Bostrom says it makes sense to assume there has been a similar mortality drop among U.S. hip replacement patients because these four methods are being used at most American hospitals. But the U.S. is still working to create a similar-sized registry that could confirm the findings.
The American Joint Replacement Registry, the official registry sponsored by the American Academy of Orthopaedic Surgeons, launched its current data collection efforts in 2012. Its long-term goal is to capture data on 90 percent of joint replacements done in the U.S., but currently it has data on only about 55,000 procedures. Slightly more than 200 hospitals have signed up for the registry so far. About half are currently submitting data and the others are in the process of setting up a system to do so.
“They are trying to start [a registry] here in the U.S., but we are really far behind,” Dr. Bostrom explains. “That’s really too bad, because we do the most joint replacements anywhere in the world and it’s a very powerful tool to figure out what is and isn’t working for the benefit of our patients.”