Magnesium-based implants: a mini-review.

Background A variety of materials have been used for bone augmentation, distraction osteotomy, and in post-cancer patients following tumor removal. However, a temporary metal implant that would resorb after successful treatment is a new concept. Magnesium was suggested as a suitable material for these purposes because it is biocompatible, has better mechanical properties than titanium, and stimulates new bone formation. Aim/Hypothesis To evaluate histological appearance of magnesium-based implants and the surrounding bone. Material and Methods Three magnesium-based biomaterials were tested in a rabbit bone defect model- magnesium hydroxyapatite (Mg-HA), W4 (96% magnesium, 4% yttrium), and pure magnesium (pure Mg). Animals were sacrificed after 6 and 12 weeks and the samples were analyzed histologically and histomorphometrically. Results Mg-HA had the highest mean amount of tartrate-resistant acid phosphatase (TRAP) positive cells at the implantation site of all groups. It had shown the fastest degradation rate already at 6 weeks but the least amount of new bone formation. New bone was seen forming in direct contact to pure Mg and W4. The mean gas volume was highest in W4 compared to pure Mg and Mg-HA but this difference was not statistically significant. W4 had the lowest mean number of TRAP-positive cells of all materials. Conclusions and Clinical Implications Pure Mg and W4 were shown to be the most promising materials in this study in respect to the bone response to the implant material. They could be used for screws and plates in bone augmentation procedures.

Magnesium and its alloys as orthopedic biomaterials: A review

In recent years, research on resorbable metal implants has gained a great deal of attention. Magnesium-based alloys have advantages in mechanical properties, biocompatibility, bioactivity, and antimicrobial potentials, but the excessive degradation rate limits their clinical applications. In order to tackle this problem, researchers have carried out various studies on surface modification techniques, and the magnesium-based screws have been certified by many countries and are now moving towards the field of clinical use. However, its clinical transformation into other orthopaedic materials still needs to solve the problem of mechanical strength as well as optimal matching of degradation behavior, where alloying and surface treatment are feasible solutions, and larger scale clinical testing and development of new types of magnesium-based implants with other functions are the directions for future research.