Abstract
Because Mg-Ca-Zn alloys are biodegradable and obviate secondary implant removal, they are especially beneficial for pediatric patients. We examined the degradation performance of Mg-Ca-Zn alloys depending on the surface modification and investigated the in vivo effects on the growth plate in a skeletally immature rabbit model. Either plasma electrolyte oxidation (PEO)-coated (n = 18) or non-coated (n = 18) Mg-Ca-Zn alloy was inserted at the distal femoral physis. We measured the degradation performance and femoral segment lengths using micro-CT. In addition, we analyzed the histomorphometric and histopathologic characteristics of the growth plate. Although there were no acute, chronic inflammatory reactions in either group, they differed significantly in the tissue reactions to their degradation performance and physeal responses. Compared to non-coated alloys, PEO-coated alloys degraded significantly slowly with diminished hydrogen gas formation. Depending on the degradation rate, large bone bridge formation and premature physeal arrest occurred primarily in the non-coated group, whereas only a small-sized bone bridge formed in the PEO-coated group. This difference ultimately led to significant shortening of the femoral segment in the non-coated group. This study suggests that optimal degradation could be achieved with PEO-coated Mg-Ca-Zn alloys, making them promising and safe biodegradable materials with no growth plate damage.
Highlights
Mg-based materials are promising in the orthopaedic field because of their various advantages, such as biodegradability [1,2,3] and biocompatibility
Before using Mg-Ca-Zn alloys in the case of pediatric patients, it is necessary to ensure that the alloy does not damage the growth plate as it may affect the normal growth of the patients carrying them
The void volumes of the plasma electrolyte oxidation (PEO)-coated alloys were noticeably smaller than those of the non-coated alloys at every time point (Figure 1B). These results suggest that the PEO-coated alloys degraded significantly more slowly than the non-coated ones and that they created significantly less hydrogen gas than did the non-coated alloys throughout the follow-up period
Summary
Mg-based materials are promising in the orthopaedic field because of their various advantages, such as biodegradability [1,2,3] and biocompatibility. They do not induce systemic inflammatory reaction [4,5]. Various attempts have been made to produce Mg alloys and modify their surface to slow the degradation rate and regulate the by-product formation [2,7,8,12,13,14] In this process, some Mg alloys even contain aluminum or heavy rare earth elements [1,10,12,14,15]. To the best of our knowledge, this study is the first investigation of the in vivo response of growth plate to biodegradable Mg-Ca-Zn alloys
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