A team of Russian scientists has determined that several rare-earth metals, which are incorporated to enhance the performance of bone implants, actually pose a risk to internal organs. This research, supported by the Russian Science Foundation (RSF), established that the inclusion of lanthanum and cerium can lead to damage in the liver and kidneys. The findings of this study have been published in the journal Materials.
In contemporary medical practice, titanium and its alloys are widely regarded as optimal materials for implants due to their inherent strength, longevity, and biocompatibility. However, even titanium structures degrade over time, compelling experts to continually explore methods for extending the service life of such constructs.
The addition of rare-earth elements—a group encompassing 17 chemical substances valued across various economic sectors—to titanium is considered a promising avenue for development. These minute additions are intended to boost the wear resistance of these medical devices, and until recently, they were presumed to be entirely safe for human recipients.
The RSF press service reported that specialists from the A.A. Baykov Institute of Metallurgy and Material Science, Russian Academy of Sciences, and the Academician G.A. Ilizarov National Medical Research Centre of Traumatology and Orthopaedics, undertook the task of validating this assumption.
The experiment involved 46 rats, which were divided into four distinct cohorts. One set received titanium implants augmented with yttrium, another with lanthanum, and a third with cerium. The control group was fitted with implants made strictly of pure, unadulterated titanium. Over the course of one month, experts monitored the subjects’ condition, meticulously documenting changes in body mass, core temperature, and local tissue response at the surgical site.
All test subjects remained in a stable condition, with no significant deviations in their body weight. However, local temperature variations were noted near the implant locations. In rodents bearing yttrium implants, this thermal measure dropped by 1.6 degrees Celsius after one week, whereas rats with lanthanum implants showed an increase of over one degree. One week later, the temperatures in all groups returned to normal. The researchers attributed these fluctuations to an inflammatory response, which was most pronounced in those receiving lanthanum implants but somewhat mitigated as time passed.
Three months following the start of the trial, blood analysis was performed. In the rats implanted with devices containing lanthanum and cerium, markers indicative of liver and kidney impairment were detected. Subjects with yttrium implants and those in the control group exhibited no such adverse changes. This outcome directly challenges the prevailing belief regarding the universal safety of all rare-earth metal additives.
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