# Bone Tissue Condition during Osteosynthesis of a
The second trend is the use of metallic biodegradable materials for the fixation of fractured bone parts. To heal acceleration, broken bones must be firmly stabilized to avoid even micro-movements under the influence of applied forces. Implants made from some metals and alloys are preferred for load-bearing applications because of their superior mechanical strength near to human bone. Magnesium and magnesium alloys exhibit good biocompatibility, mechanical strength, and biodegradation properties and may be used as materials for the production of temporary implants [5; 12]. The products of the dissolving alloys are friendly to the human organism. Magnesium has an elastic modulus of about 45 GPa, a value close to that of bone (15-25 GPa). Mg alloy density is between 1.74 and 1.84 g/cm\({}^{3}\), depending on the alloying components, being almost equal to the one of human bone (1.8-2.1 g/cm\({}^{3}\)). Unfortunately, magnesium alloys are susceptible to corrosion in physiological aqueous media and need protection [13]. Surface modifications are useful, mainly for slowing the corrosion process, but also for clinical needs regarding biodegradable Mg alloys. Special coatings need to be created on the magnesium surface to equilibrate the implant corrosion and bone tissue formation rates. From the electrochemical surface modification class, plasma electrolytic oxidation (PEO) forms a protective ceramic-like coating on the treated magnesium alloys [14; 15; 16; 17]. The formation of calcium phosphate and polymer-containing coating are aimed at improving both the corrosion protection of the Mg alloy and at providing biocompatibility of the metallic implant [18]. According to results of prior in vivo experiments [19], magnesium alloy does not cause any negative effects during resorption in a rat body. Effects of long-term degradation of magnesium implants in vivo on continuous bone tissue growth in a rat skeleton were also reported [20]. Moreover, it is well accepted that coupling and synchronization of material resorption and bone healing is conducive in maintaining mechanical stability and subtle biological responses, thereby achieving homeostatic balanced implant dissolution and complete osteosynthesis or reconstruction [21]. In this work, we used as a substrate the MA8 magnesium alloy with small amounts of alloying elements Mn (1.5-2.5 wt %) and Ce (0.15-0.35 wt %). This material is one of the slowly degrading magnesium alloys, and its alloying elements are not harmful to the human organism [15; 22]. The authors found that bone recovers after complete degradation of the magnesium implants made from the alloys with manganese and rare earth elements. The degradation of the Mg alloys generates a significant increase in Mg concentration in the cortical bone near the remaining implant parts, but the Mg accumulation disappears after the implant degrades completely. Moreover, it was established that the hydrogen gas formation and ion release during magnesium implant degradation did not harm bone regeneration and the organism state in whole. The evacuation of degradation products from the organism was realized rather quickly. Surgical treatment of fractures in patients with osteoporosis requires minimizing possible reoperations. Evaluation of the effectiveness of using biodegradable implants, in this case, is of particular interest [19]. This work aims to study the features of the reparative potential of bone tissue during osteosynthesis of a fracture in the femoral shaft in the case of using a magnesium implant with a bioactive layer and in the case of using a bioactive and anticorrosive layer. The studies were carried out on Wistar rats with a model of osteoporosis. In one group of rats, biodegradable magnesium alloy implants coated with hydroxyapatite without polytetrafluoroethylene were used. Another group used hydroxyapatite-coated implants sealed with polytetrafluoroethylene.