Plasma electrolytic oxidation-treated magnesium 합금이 이식된 토끼 대퇴골 및 척추옆근육 부위에서의 생체 적합성 평가

Abstract

Ti and stainless-steel internal fixation devices have been the gold-standard for orthognathic surgery and for repairing craniofacial fractures. However, these materials can lead to long-term complications such as tissue irritation, infection, radiographic image interference, skeletal growth interference (especially in pediatric patients), aesthetically undesirable features (mainly craniofacial implants), and thermal sensitivity, as well as the potential requirement for a second surgery to remove the fixation material. Recently, magnesium alloys have been receiving much attention for use in biodegradable metal implants because of their excellent mechanical properties and biocompatibility. However, their rapid breakdown and low bioactivity can cause the implant to lose mechanical integrity before the bone is completely healed. Moreover, hydrogen gas released during degradation can significantly delay the tissue regeneration process. To solve the instability of magnesium alloys, Zn and Ca can be added to improve the mechanical properties and biocompatibility. Thus, in our study, 1 wt% Zn and 0.3 wt% Ca were added to the Mg melt to increase the melt fluidity and promote the mechanical properties and corrosion resistance of this porous material as much as possible. One other way to improve the mechanical properties of Mg is plasma electrolytic oxidation (PEO), which provides a dense, thick ceramic-like coating on the Mg surface. In this study, high-purity Mg was selected as the control, and Mg1Zn0.1Ca and PEO-treated Mg1Zn0.1Ca were selected as the test materials; the results of radiographic and histological analyses of their biocompatibility are reported herein. Nineteen New Zealand white rabbits were used in the study. Rod-bars (Ø2.7x13.6mm) were placed on both paravertebral muscles, and cannulated screws (Ø2.7x10mm) were placed on both femur condyle notches. Each animal was implanted in all four sites. X-rays were taken at 0, 2, 4, 8, and 12 weeks, micro-CT, and live-CT were taken at 4, 8, and 12 weeks. At weeks 4, 8, and 12, individuals representing each group were selected and sacrificed to prepare specimens for histopathological examination. The results confirm that in vivo, Mg1Zn0.1Ca had higher corrosion resistance than high-purity Mg and safely degraded over time without causing possible side effects (foreign body or inflammatory reactions, etc.). In addition, PEO treatment of Mg1Zn0.1Ca had a positive effect on fracture recovery by increasing the bonding area with bone. Based on the results of this study, clinical studies on large animals are needed before this technique can be applied in humans.