Degradable Magnesium Alloys as Novel Bone Implants
Among three major
classes of biomaterials: metals, ceramics, and polymers, the metals have gained
popularity for load-bearing applications due to their high stiffness and
mechanical strength, compared to polymers and ceramic materials. Thus, metallic
implants based on Ti (Ti6Al4V), Co-Cr alloys, and stainless steel (SS316L) have
been used for more than a decade by clinicians for orthopedic reconstruction.
However, a strong mismatch between the elastic moduli and tensile strengths of these
metals and natural bone causes stress shielding effects resulting in the
weakening and consequent fracture of the surrounding bone. In addition,
the long-term use of current inert metal implants often requires invasive
secondary surgery to prevent the side effects from wear debris causing
metallosis and other related foreign body response. Adult patients are likely
to undergo secondary removal surgery only in the case of any eventual complication.
On the other hand, pediatric patients are highly likely to require secondary
surgeries to remove the implants interrupting bone growth. Therefore, the
development of biodegradable metal implants to overcome the limitations of
current clinical solutions is of high interest in the field of orthopedics and
regenerative medicine. Biodegradable Mg alloy based implant devices will resorb
in a controlled fashion thus overcoming the limitations of current metallic
implants while keeping the advantage of higher stiffness and mechanical
strength. Our group over the past 10 years is working to develop various Mg
based alloys with improved bio-corrosion resistance and bio-mechanical
properties. In addition, various fixation devices have been developed and
tested for their local and systemic toxicities.
Bone fixation devices made of Mg alloys
(a). Photographs of plate and screws; and (b). Low magnification SEM images of
a representative porous bone scaffolds.
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