Written by Emre Ertugrul
The association between high-viscosity bone cement and knee implant failures
The usage rate of high-viscosity bone cement in primary total knee replacement surgeries in the United States increases steadily while recent studies indicate the association between early failures in the post-surgery period and the high-viscosity cement – a trend in which the reason remains unclear.
Thousands of Americans undergo knee replacement surgeries each year, a considerable percentage of which suffer from aseptic loosening in the aftermath due to several complications. Early failures following the total knee arthroplasty happen via debonding at the tibial implant-cement interface, which is the main part that requires a physician to determine the viscosity level of the bone cement.
Cement viscosity plays a key role.
Although prior investigations point out low viscosity cement as a much more effective solution, a blast of advertisements in recent years and the time benefit for surgeons have driven high-viscosity cement forward for primary total knee arthroplasty.
A 2012 research on the effect of cement viscosity has shown a consistently superior performance by the medium viscosity cement compared to high-viscosity cement. According to the study, Simplex P, a medium viscosity cement, had the maximum penetration in several parts – a result that is deemed “significant” when compared to Palacos R, a high-viscosity cement.
While the association between high-viscosity bone cement and early failures has been confirmed, the usage rate of the cement has increased from 46 percent in 2012 to 61.3 percent in 2017, after a seven-year review of a total of 554,935 primary knee replacement surgeries, according to a July 26 article published in The Journal of Arthroplasty.
The study, conducted using data by the American Joint Replacement Registry, showed that the use of low viscosity bone cement decreased from 47.9 percent to 30.9 percent in the same respective years. The results stated that the steady increase in the use of high-viscosity cement poses further monitoring to determine whether the cement type affects aseptic loosening or not.
While clinical studies project the contrariety of the physicians’ high-viscosity preference and the possible link between high-viscosity cement and early failures, more legal actions against manufacturers are expected to come.
Attorney Christopher Kyle Johnston, who described the trend as “definitely worrisome,” said in an interview that the increase in the percentage of high-viscosity usage points out more injuries in the upcoming years with more legal claims.
Johnston, who is the founder of the Johnston Law Group, said that most of the time, the debonding occurs for the tibial component due to lack of strength.
“The main allegation is that the bond between the cement and the component is not strong enough,” he said. “It’s as simple as that.”
One remarkable claim that he has encountered was a client’s inevitable amputation following revision surgeries. Due to multiple surgeries that his client had to undergo, he had no choice but to have his leg amputated.
Every step of surgery will make the patient lose a part of the bone, Johnston said. “And it comes into a point in which you don’t have more bone which they [surgeons] can take out and put another implant, and the result would be the amputation of your leg – which is more common than people tend to think.”
Even though The Journal of Arthroplasty’s article has numbered the increase rates, the report also states that “incomplete data in the revision cases prevent analyzing the association between cement type and revision surgery.” In addition, the study conducted was based on certain data from the American Joint Replacement Registry, which only has a certain amount of information providers registered.
“If you take that into consideration, the percentage of the increase could be bigger,” Johnston said when asked about the possible increase rate in the future.
Why use it?
Despite the risks of high-viscosity cement debonding and its questionable efficacy, there are several factors for physicians to go for it during the surgery. According to arthroplasty studies, surgeons prefer high-viscosity cement because of its fast mixing and waiting phases compared to lower viscosity cements. While there is still no concrete explanation of what caused the trend in high-viscosity usage, manufacturer promotion, surgeon preference and new implant designs concomitant for high-viscosity have been considered the main possible reasons.
Johnston said that the combination of the implant type, the cover of the implant, the design and the bone cement used are very crucial points to take into consideration when trying to determine the cause of the loosening.
The compatibility of the materials used in the surgery has not been studied and can make a difference, he added, and the pore size in different cements and penetration and hardening phases might as well affect the bonding of the implant; however, there has not been enough studies to review the compatibility of different factors.
Is it the proven factor?
Aside from conclusions that underline the association between early failures and high-viscosity cement, there is still no deduction that can determine the high-viscosity cement as the factor that causes aseptic loosening after the surgery.
“I cannot tell a patient that it’s going to happen,” Johnston said. “You can’t say it’s proven that high-viscosity cement causes debonding, but it’s definitely something that patients should be aware of before going to the surgery.”
Johnston added that lower viscosity cements are much more reliable and safer for patients, although the usage rates have decreased drastically.
“I’d recommend all doctors and patients to stop using this cement until further studies are done,” he said.”
Emre Ertugrul
Emre Ertugrul is a reporter for Safetywatch.org, covering controversial drugs and medical devices, reporting on health policy and the FDA. He studied journalism with concentration in investigative reporting at Boston University. Previous experience with the New England Center for Investigative Reporting include tax issues, racial profiling and criminal justice. He also worked as an international news intern at Milliyet Newspaper and is currently one of the editors for Gazet.com.
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