A Michigan hospital puts implants through the paces using lifelike simulation technology to assess longevity.
The wild card in artificial hip implants has always been device longevity. Now, thanks to emerging technology that advances the science of hip implant simulation, surgeons may be better prepared to predict how a given device will endure.
Simulating the wear and tear that an artificial hip will encounter is crucial, given the new variety of implants on the market, says James Verner, MD, a joint replacement orthopedic surgeon at Beaumont Hospital in Royal Oak, MI. "The traditional replacement hip has been metal on plastic," he says. "Now we are looking at metal on metal, and ceramic on ceramic on ceramic designs. There has not been a lot analysis to date on how well these materials will perform."
Verner is heading up an effort at Beaumont’s Orthopedic Research Laboratory that uses advanced computer technology to measure the wear and tear on joint replacement devices. Manufactured by MTS Systems, an Eden Prairie, MN-based company, the technology uses a 12-station simulator to imitate actual human use. Unlike earlier testing methods, which require continuous testing, the Instron device mimics the start-and-stop motion humans actually go through in daily living.
The average patient takes a million steps in a year, Verner says. The simulation technology could be programmed to mimic a million steps and accomplish the test in four weeks. Or it could take several months to test a potential replacement hip, with resting periods built into the test. Potential implants are loaded into the machine, which bathes the device in a protein serum that simulates joint fluid. In addition to assessing wear under moving and resting conditions, the technology also offers improvements in measuring how well the device responds to changes in pressure and orientation. The data is valuable to orthopedic surgeons, who must calculate the positioning of implants before surgery, Verner says.
The hip simulator is flexible technology that can test other replacement parts, Verner says; a colleague, Michael Wiater, MD, is beginning to study shoulder replacements using the device. Beaumont, which staffs 1,061 beds, is part of a three-hospital health system that includes an academic medical center and two community hospitals. The health system will use the technology to test new devices on behalf of manufacturers, Verner adds. "The public is sometimes skeptical about the data," he says. "We want to verify the data that the manufacturers have been quoting."