Resorbable Magnesium Hardware for Bone Fractures

Each year in the US there are about 6 million bone fractures, of which approximately one third require internal fixation to stabilize the healing bone. Typically, fixation involves plates and screws made of non-degrading metals — such as titanium and stainless steel — but these metals can cause bone loss, pain, and interferences with future surgical procedures. Patients may require a subsequent removal surgery. Sometimes, instead of screws and plates, surgeons use Kirschner wires (K-wires), which are often left to protrude through the skin for easy removal,but carry a complication rate of up to 42 percent. In search of an impermanent method for fixating bones, some researchers have explored degradable polymers, but these materials tend to be too weak to handle the necessary load. Our resorbable magnesium alloy has sufficient mechanical strength to directly replace traditional bone fixation hardware, while also being able to resorb over time.

Description

Each year in the US there are about 6 million bone fractures, of which approximately one third require internal fixation to stabilize the healing bone. Typically, fixation involves plates and screws made of non-degrading metals — such as titanium and stainless steel — but these metals can cause bone loss, pain, and interferences with future surgical procedures. Surgeons use Kirschner wires (K-wires), which are often left to protrude through the skin for easy removal, but carry a complication rate of up to 42 percent. By mixing magnesium with other metals — including yttrium, calcium, and zirconium — we can tailor the mechanical strength and rate of degradation to suit the properties of the healing bone. Since magnesium alloys are softer than titanium or steel, we had to redesign the shape of traditional bone screws to avoid breakage during insertion. When tested on fractured rabbit ulnae, our magnesium-based fixation hardware stimulated new bone growth, which completely covered the degrading hardware in 16 weeks. Bend tests revealed that this healed bone could handle the same load as bone that were never fractured.

Applications

- Orthopedics (pins, screws, plates, K-wires, or cerclage wires)
- Craniofacial reconstruction
- Cardiovascular stents

Advantages

- Biocompatible
- Osteoinductive, stimulates bone growth
- Biodegradable
- Comparable strength to traditional metals

Invention Readiness

In vivo data

IP Status

https://patents.google.com/patent/US20230381382A1

Related Publication(s)

Chaya, A., Yoshizawa, S., Verdelis, K., Myers, N., Costello, B. J., Chou, D.-T., Pal, S., Maiti, S., Kumta, P. N., & Sfeir, C. (2015). In vivo study of magnesium plate and screw degradation and bone fracture healing. Acta Biomaterialia, 18, 262–269. https://doi.org/10.1016/j.actbio.2015.02.010

Henderson, S. E., Verdelis, K., Maiti, S., Pal, S., Chung, W. L., Chou, D.-T., Kumta, P. N., & Almarza, A. J. (2014). Magnesium alloys as a biomaterial for degradable craniofacial screws. Acta Biomaterialia, 10(5), 2323–2332. https://doi.org/10.1016/j.actbio.2013.12.040