Magnesium Alloy
Bone Screw
The main drawback of traditional magnesium bone screws is the rapid degradation rate, causing the magnesium bone screw to degrade and dissolve before sufficient bone growth occurs. The usual solution involves "alloying and surface treatment" of the bone screw. Since 2014, Kuangyue has been collaborating with the Taiwan Metal Industry Research & Development Center to conduct experiments. Together with Taipei Medical University, they have co-developed a high-purity magnesium material to manufacture non-toxic magnesium bone screws. These screws are treated with a "coating of bio-absorbable degradable polymeric material" to slow down the rapid degradation of traditional magnesium bone screws. This approach has led to the acquisition of both invention and utility model patents.
To address the rapid degradation issue, we employ alloying and surface treatment techniques, implanting AZ31&ZK60 magnesium alloy into New Zealand rabbit femurs for testing. Monitoring the condition of the implanted magnesium bone screws each week, untreated ZK60 group exhibited significant gas cavity formation 1-2 weeks post-implantation. The surface-treated ZK60 group showed a similar situation at 2 weeks but slowed down by the third week. In contrast, the untreated ZK60 group continued expanding gas cavities until improvement around the 5th week. The AZ31 group had less noticeable gas cavity formation.
For alloying and surface treatment elements in medical materials, potential unknown impacts on the human body exist. To mitigate potential harm, our research team collaborated with Taipei Medical University to develop high-strength magnesium bone screws using high-purity magnesium material as a substitute for alloying elements. In 2015, we obtained a patent for high-purity, high-strength magnesium bone screw material.
Research indicates that pure magnesium bone screws do not affect stem cell differentiation, with a much higher cell proliferation rate, making them safer and more effective. However, the challenge lies in their rapid degradation, hindering support until bone growth completion.
To overcome this, we continue developing a method involving a coating of bio-absorbable degradable polymeric material to slow down the degradation rate. These materials can be absorbed by the human body without toxicity and are already in use in commercially available bone screws and plates in the market.
Polylactic acid-coated pure magnesium bone screws have the following advantages:
-
Non-toxic and biocompatible for the human body
-
Prolongs degradation time
-
Maintains a neutral environment during degradation
In terms of production technology, Kuangyue has obtained invention patents on both sides of the strait. We use ultrasonic heads to join screws and apply energy to induce phase changes, causing them to dissolve and embed into tissues. Through experiments involving tests on the acidity of pure magnesium and the co-cultivation of magnesium ions with cells, it has been confirmed that PLA-coated pure magnesium bone screws can slow down degradation, increase the strength of magnesium metal in the screws, and exhibit uniform thermal conductivity in bone screw thermal conductivity tests.