Biodegradable implants a win-win for everyone, says prof at TAMU-Q

A research group at Texas A&M University at Qatar has made great strides towards developing next-generation orthopedic implants that not only possess excellent strength but are also biodegradable.

“Biodegradable implants support a broken bone as it heals, degrade in a timely manner and ’disappear’ completely once the healing is complete,” said Dr. Bilal Mansoor, Associate Professor of Mechanical Engineering at the Qatar Foundation partner university, who is leading the research group. This potentially means elimination of implant removal surgeries, which will result in reduced stress and recovery time for the patient.

“For healthcare providers, it will mean more prudent use of a surgeon’s time as well as healthcare resources — a win-win situation for everyone involved.”

Magnesium, a biocompatible and naturally occurring metal in the human body, is a seemingly perfect choice of material for biodegradable implants, except it suffers from an undesirably high rate of corrosion, or degradation, in the human body. The challenge is to slow down its rate of corrosion, so the magnesium-based implant maintains its mechanical strength over the desired period.

Dr. Mansoor suffers from fibrous dysplasia, a rare disorder which results in the weakening of bones. To treat his condition, he had an implant inserted in his right leg back when he was in university. “I clearly remember what a massive improvement the implant made to the quality of my life. I felt like I could finally live a normal active life of which excruciating pain was no longer a part. That is what sparked my interest in implants,” he said.

Orthopedic implants are routinely used in healing bone fractures. In most circumstances, a bone fracture requires a surgery wherein the broken bone pieces are realigned and held in place using a metallic implant (plate, screw, wire or pin). Conventional metallic implants are typically made of titanium or stainless steel and require a second surgery to be removed once the bone has healed. Biodegradable implants, on the other hand, do not require surgery to be removed making them particularly useful for children and elderly patients.

“Magnesium’s high rate of corrosion results in loss of mechanical integrity in the implant before the bone fracture has completely healed,” Dr. Mansoor said, and he believes microstructure design is the key to unlocking the potential of magnesium alloys as a viable material in the field of biodegradable implant materials.

His team has successfully fabricated refined microstructures in magnesium alloys using friction stir processing (FSP), a novel material processing technique that leads to microstructural modifications resulting in improved mechanical properties.

“The magnesium alloys that we prepared using FSP exhibit a 50 percent improvement in strength as compared to that of conventional magnesium alloys, while retaining similar degradation profiles,” Dr. Mansoor said.

To test the performance of the prepared alloys, Dr. Mansoor collaborated with Hamad Medical Corporation (HMC) and Qatar University (QU). Cytotoxicity tests done at HMC confirmed that the alloy extracts were not cytotoxic to normal cells, with the implantation of the alloy in rats being done in a humane study at QU and periodic CT scans at TAMUQ confirming the complete healing of their bones, and new bone formation, in eight weeks.

Dr. Talal Ibrahim, Acting Division Chief of Orthopedic Surgery at Sidra Medicine, notes that the use of metallic implants is very common in orthopedic surgery. “In children, metallic implants are usually removed at a later stage and this is done under general anesthesia. The use of biodegradable implants in this population can be very useful in avoiding further operations that are associated with risks and save resources,” he said.

The project has also received attention from Qatar Foundation’s Equine Veterinary Medical Center (EVMC). “Use of biodegradable screws is a fast-moving field of research in equine surgery, with a wide range of therapeutic uses, such as for certain types of fractures, correction of angular limb deformities, as well as for the treatment of bone cysts. However, their drawback is their poor strength and bone-holding capacity for use in horses, and so the resorbable magnesium alloys designed by Dr. Mansoor and his team at TAMU-Q is an exciting prospect for us,” said Dr. Jessica P. Johnson, Senior Clinical Veterinarian, EVMC.

The project was funded by Qatar National Research Fund, and it offers Dr. Mansoor and his colleagues the potential to bring about tangible improvements in health care. “Once developed, these novel biodegradable magnesium alloys could be deployed therapeutically in a range of orthopedic, cardiovascular and tissue engineering scaffold applications, with significant societal and economic impacts for the State of Qatar,” Dr. Mansoor said.