Amy Chaya, BS, Sayuri Yoshizawa, DDS, PhD, Kostas Verdelis, DDS, PhD, Sabrina Noorani, MS, B.J. Costello, MD, DMD, Charles Sfeir, DDS, PhD
Purpose Internal bone fixation devices made with permanent metals are associated with numerous long-term complications and may require removal. We hypothesized that fixation devices made with degradable magnesium alloys could provide an ideal combination of strength and degradation, facilitating fracture fixation and healing, while eliminating the need for implant removal surgery.
Methods Fixation plates and screws were machined from 99.9% pure magnesium and compared to titanium devices in a rabbit ulna fracture model. Magnesium device degradation and effect on fracture healing and bone formation was assessed after four weeks. Fracture healing with magnesium device fixation was compared to that of titanium devices using qualitative histological analysis and quantitative histomorphometry.
Results Microcomputed tomography showed device degradation after four weeks in vivo. In addition, 2D microCT slices and histological staining showed that magnesium degradation did not inhibit fracture healing or bone formation. Histomorphology revealed no difference in bone bridging fractures fixed with magnesium and titanium devices. Interestingly, abundant new bone was formed around magnesium devices, suggesting a connection between magnesium degradation and bone formation.
Conclusion Our results demonstrate potential for magnesium fixation devices in a loaded fracture environment. Furthermore, these results suggest that magnesium fixation devices may enhance fracture healing by encouraging localized new bone formation.