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Bone regeneration is one of the most complex and unique types of tissue regeneration, although quite long in time, comparatively, for example, with soft tissues, but provides the complete identity of the damaged site with normal bone. The most complex fractures are fragmentation, which can be occurs within wide range - 25-60% of the total number of all fractures. In such cases, due to the loss of contact with soft tissues, the fragments lose blood supply and regeneration, which leads to different bone size defect. This condition cause limitation of the main mechanisms of bone consolidation – endoostal and intramembrane ossification. In this regard, a strategic medical treatment is the replacement of bone defect with biological or synthetic material, which creates a site for the processes of reparative osteogenesis. The most widespread combined biocompatible materials in the various combinations of β-tricalcium phosphate and hydroxyapatite ("Maxresorb®", "Perossal®", "calc-i-oss®CRYSTAL", "easy-graft®CRYSTAL"), or composite composites based on bioactive and biogenic materials: hydroxylapatite + collagen (Biostite, Collagraft, Avitene, Collola, Hapkol, Collapan, MP Composite); hydroxylapatite + tricalcium phosphate + collagen ("Hydroxyapol", "Collapolum"); hydroxylapatite + collagen + sulfated glycosaminoglycans ("Biomatrix", "Osteomatrix", "Bioimplant"). Unfortunately, in veterinary medicine osteotropic materials developed for humane medicine are used only. Recently, a separate group of biocompatible composites based on the combination of hydroxyapatite with β-tricalcium phosphate, doped with magnesium, sodium, potassium, zinc, copper, aluminum, strontium, silicon, germanium, in order to provide them with specific properties - antibacterial, osteoinductive, antitumor, immunomodulating, etc. However, the spectrum of biological effects of these ions on bone metabolism is extremely diverse, and therefore the use of composite ceramics doped with microelement ions requires a comprehensive clinical and experimental justification. The purpose of the study is to evaluate the osteointegration and osteoinductive properties of ceramics based on hydroxyapatite and β-tricalcium phosphate doped with silicon for model fractures of the femur in rabbits. The work is done on rabbits of Californian breed at the age of 3 months. and a weight of about 2.5 kg. To substantiate the ceramics GTlKg-2, 2 groups of 10 rabbits were formed in each, in which model bone defects were formed in the distal parts of the hip dysthymia. Animals of the experimental group defects filled with granules of ceramics. In the rabbits of the control group, the defect was left to heal under a blood clot. Animals were extracted from the experiment at the 21st and 42nd day. X-ray and histomorphological studies were performed. On the 21st day of reparative osteogenesis, rabbits of all groups fully rested on the injured limb, signs of inflammatory reaction were absent in the experimental group, and the control marked the pronounced seal of the periosteum across the entire surface of the femur. It should be noted that hydroxyapatite ceramics does not possess x-ray contrast properties. On the 42nd day of regeneration of rabbits both groups fully rested on injured limb, signs of inflammatory reaction of soft tissues in the area of injury were absent. Radiologically, in animals of the experimental group in the place of bone defect, spot osteosclerosis was detected in the form of a clearly defined white heel, opposite to which the contour of the periosteum was sealed. At the same time, on the control X-rays, along with a well-defined, but more elongated septum of the periodontal, revealed a bone marrow panossus at the site of the injury, with a clearly defined extension of the eclipse. Substantially complemented macromorphological picture of bone biopsy. In particular, in the case of replacement of bone defect GTlKg-2, at the 21st day in the traumatic areas a limited and moderate periosteal reaction was noted. Along with this, in control animals, in this period, it was not completely replaced by fibrous cartilaginous tissue, as evidenced by its craterial appearance. Histologically, in the control animals, the bone defect formed a cartilage tissue along the periphery, and the bone beams, which were at a certain distance from the place of the defect, were at the stage of resorption. In the case of its replacement granules GTlKg-2 formed bone-ceramic regenerate, that is, the intervals between the granules are filled with bone tissue. The obtained results give grounds to consider that GTlKg-2 contributes to the formation of bone tissue due to its osteointegration and osteoinductive properties. Key words: reparative osteogenesis, osteointegration, osteocytes, osteoblasts, hydroxyapatite composite with β-tricalcium phosphate, doped with silicon.

Metal structures for osteosynthesis available in veterinary orthopedics are not able to compensate for the lost elements of bone tissue in complex splinter fractures. It is prompt the use of hydroxyappatite materials that replaced bone defects for maintenance of osteoconductive function, and ideally would combine osteointegration and osteoinductive properties. However, their influence on the biological processes of fracture consolidation which go through a number of successive stages and end with the formation of bone tissue in the fracture zone identical to the maternal, is insufficiently substantiated according to the criteria of the molecular biological phase of reparative osteogenesis. The aim of the study was to investigate the dynamics of biochemical osteotropic parameters and the level of NO using silicon-doped ceramics for fractures heeling in dogs. Materials and methods. The animals suffering of fractures that were admitted to the faculty clinic were divided into control (n=7) and experimental (n=7) groups. In both groups, extracortical osteosynthesis was performed with a support plate from an unalloyed titanium alloy. In the control group, bone defects were left to heal under spontaneous blood clot, and in the experimental group, they were replaced with ceramic based on hydroxyapatite with β-tricalciumphosphate doped with silicon (HA/β-TCP/l-Si–3).Blood samples were taken after the injury no later than the 48th day, and on the 3th, 12th, 21th, 42th and 60th days after osteosynthesis. To increase the objectivity of the biochemical analysis, we additionally formed a group of clinically healthy dogs that were admitted to the clinic for routine vaccination (n=10). It included the spectrophotometric determination of the content of NO, BALP, TRACP, Ca, P, Mg, total protein in blood serum, and fibrinogen in blood plasma. Research results. A clinical study showed that in the case of using HA/β-TCP/l-Si–3for splinter fractures, the stages of reparative osteogenesis are more optimized in time, and their consolidation occurs on average 19 days earlier than in the control group. The results of the biochemical study showed that when using HA/β-TCP/l-Si–3, it is accompanied by a peak NO value already on the third day, which is significantly higher than in the control group and indicates early angiogenesis in the research group. In terms of TRACP, the period of osteoresorption in the control group was permanent with little expressed peaks of activity. However, in the research group, the peak of TRACP activity is limited to 12 and 21 days, which is evidence of an optimized inflammatoryresorptive phase. In parallel with this, the activity of BALP increases, which indicates the consistency of the stages of reparative osteogenesis and provides an optimized and accelerated consolidation of fractures in the research group. Conclusion. The dynamics of NO, BALP and TRACP pathochemically substantiates the optimized reparative osteogenesis when using HA/β-TCP/l-Si–3 for bone defects replacement in cases of splinter fractures of tubular bones. Key words: bone markers, bone isoenzyme of alkaline phosphatase, NO, tartrate-resistant acid phosphatase, fibrinogen, calcium, phosphorus.

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