The effect of different coatings on bone response and degradation behavior of porous magnesium-strontium devices in segmental defect regeneration.

Abstract

Regeneration of long-bone segmental defects remains a challenge for orthopedic surgery. Current treatment options often require several revision procedures to maintain acceptable alignment and achieve osseous healing. A novel hollow tubular system utilizing magnesium-strontium (Mg-Sr) alloy with autogenous morselized bone filled inside to repair segmental defects was developed. To improve the corrosion and biocompatible properties, two coatings, Ca-P and Sr-P coatings, were prepared on surface of the implants. Feasibility of applying these coated implants was systematically evaluated <i>in vitro</i> and <i>in vivo,</i> and simultaneously to have a better understanding on the relationship of degradation and bone regeneration on the healing process. According to the <i>in vitro</i> corrosion study by electrochemical measurements, greater corrosion resistance was obtained for Ca-P coated sample, and attributed to the double-layer protective structure. The cytotoxicity and alkaline phosphatase (ALP) assays demonstrated enhanced bioactivity for Sr-P coated group because of the long-lasting release of beneficial Sr²⁺. At 12 weeks post-implantation with Mg-Sr alloy porous device, the segmental defects were effectively repaired with respect to both integrity and continuity. In addition, compared with the Ca-P coated implant, the Sr-P coated implant was more proficient at promoting bone formation and mineralization. In summary, the Sr-P coated implants have bioactive properties and exceptional durability, and promote bone healing that is close to the natural rate, implying their potential application for the regeneration of segmental defects.