No abstract

UDC 548.73:549.753.1 Using x-ray diffraction, electrothermal atomization atomic absorption spectroscopy, and scanning electron microscopy with an x-ray microanalysis, we have studied the phase decomposition of biogenic and synthetic Mgcontaining apatite at 900 o C with formation of β-tricalcium-magnesium phosphate (β-TCMP). Employing simplified model representations, we obtained a relation that couples the initial Mg concentration with the degree of transformation of apatite into β-TCMP. It is shown that for the β-TCMP contents measured in bioapatite samples and on replacement of calcium by magnesium to about 8% in this phase the calculated range of Mg concentrations coincides with that available in literature sources (0.2-0.6 wt. %). A comparative investigation of the products of decomposition of biogenic and synthetic apatite by the methods of analysis of the composition and structure has established that the formation of β-TCMP is limited by both the insufficient concentration of magnesium and the small sizes of the crystals. The results of the investigations carried out together with the experimental data known from the literature are indicative of the nonuniform distribution of magnesium in the bulk of crystals of biogenic and synthetic apatite, with its predominant localization at the surface sites of the lattice.

None of the methods of osteosynthesis provides the consolidation of bone fragments which have lost contact with soft tissues. It makes extremely difficult treating of this type fractures. Bone defect between the fragments and absence of a primary biological matrix complicates revascularization, causes long-term life of the connective tissue and cells of cartilaginous phenotype in the fracture zone. It is leads to a long-term consolidation of the fracture. Composites of hydroxyapatite and calcium phosphates are considered as bioactive and therefore the most promising for bone defects replacing. The aim of this investigation was clinical, radiological and hematological evaluation using of silicon-doped ceramics for fragmented bone fractures in dogs. For study was chosen dogs with accidental fragmented fractures of tubular bones which treated by extracortical osteosynthesis method. Animal was divided into two groups. A bone defects were filled with ceramics (GTlKg-3) for experimental animal group (n = 7), while no filling of bone defects in control animal group(n = 7) was performed. Protocol of anesthesia included medetomidine, butorphanol tartrate and epidural anesthesia with 2 % lidocaine solution. Animals of the control group began to lean on the injured limb from the 12–15th day after surgery, while the animal of research group from the 8-9th day. Complete limb repair in dogs of the control group occurred on the 38–42th day, but such period for experimental group animals was shorter – 25–27th day after the osteosynthesis. X-ray investigation (60th day) of experimental group dogs showed new formed bone tissue with osteosclerotic zones without a periosteal reaction, bone tissue, with a normal view of the epiphyseal areas and the bone marrow cavity. This is evidence of localized reparative osteogenesis (within bone trauma only), and completed fracture consolidation. At the same time in cases of the control group we found lower X-ray density of new bone, periosteum was thickened with excessive proliferation of the endosteum, especially below the site of bone injury. Thus, in case the absence of hydroxyapatite matrix in bone defects there were compensatory increasing proliferation of periosteum and endoosteum. Fragmented fractures of tubular bones in dogs have occurred by erythrocytopenia, that quickly disappear due to the reparative osteogenesis in dog of experimental group. These animals have had leukocytosis increasing due to the first three days after osteosynthesis as a reaction to the implantation of a calcium-phosphorus composite material. Dogs of control group have had second wave of leukocytosis increasing on forty-second day associated with elongated remodeling process. Areparative osteogenesis can be accelerated in 1.5 times in case of replacement of bone defects with silicon doped hydroxyapatite ceramics. It is possibility realized thru moderate reduction of active phase of inflammation and acceleration of proliferative phase, mainly from endosteum side with early mineralization of bone regenerate. The dynamics of hematology parameters is a typical for the tubular bone consolidation that indicates about moderate inflammation and demonstrate biological tolerance of silicon-doped hydroxyapatite ceramics.

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.

Complex comminuted fractures are accompanied by development of bone defects and loss of reparative potential of the bone tissue in the region of the trauma. This brings the necessity of using implants with optimum osteoconductive and osteointegration properties. The objective of the study was determining the condition of biochemical bone markers and peculiarities of histomorphological changes under the influence of ceramic hydroxyapatite (HA) implants with various physical-chemical properties in the conditions of diaphyseal bone defects in rabbits. We composed control and experimental groups of rabbits with 10 individuals in each with diaphyseal bone defects (3 mm) of the radial bones formed under general anesthesia. In one experimental group, they were filled with granules of hydroxyapatite with α-tricalcium phosphate, and in the second group – with β-tricalcium phosphate, alloyed with Si. In the control rabbits, the defects healed under a blood clot. Blood was analyzed on the 3rd, 7th, 14th, 21st and 42nd days, and as reference we used biochemical parameters of blood of clinically healthy rabbits (n = 10). Bone biopsied materials were taken on days 21–42 under general anesthesia. When using hydroxyapatite with β-tricalcium phosphate, alloyed with Si, we determined early intensification of the levels of nitrogen oxide, angiogenesis and development of bone regenerate in conditions of shortening of inflammatory resorption phase, which was verified according to the level of tartrate-resistant acid phosphatase. According to the level of bone isoenzyme of alkaline phosphatase in the blood serum of animals of the control group, the reparative osteogenesis developed slowly and peaked on day 42, whereas in animals implanted with α-tricalcium phosphate, its development peaked peaked on days 14–42, and when using Si-alloy – on days 7–14. Histomorphologically, on the 21st day, in the case of replacement of bone defect with hydroxyapatite with α-tricalcium phosphate, coarse-fibered type of bone regenerate developed with no dense contact with the elements of the regenerate, while spongy bone trabeculae occurred when hydroxyapatite was applied with β-tricalcium phosphate alloyed with Si, and the control rabbits were observed to be in the stage of cartilaginous callus. On the 42nd day, under the influence of implants of hydroxyapatite with α-tricalcium phosphate, the spongy bone tissue transformed into compact tissue with further mineralization. With implants alloyed with Si, there occurred compact bone tissue, and bone regenerates of the control animals were regions of coarse-fibered and spongy bone tissue without dense contact with the parent bone. This study revealed that hydroxyapatite with β-tricalcium phosphate alloyed with Si had notable osteoinductive and osteointegrating properties, as indicated by early angiogenesis and osteoblast reaction, positive dynamics of the marker biochemical parameters with faster and better development of bone regenerate as spongy bone trabeculae.

No abstract

Among several factors that can cause a violation of the course of reparative osteogenesis, previous diseases associated with a change in the structural and functional state of bone tissue and primarily osteoporosis are considered significant. Osteoporotic fractures are difficult to treat. Along with systemic therapy, locally applied bone substitute materials, particularly unalloyed and alloyed calcium phosphate ceramics with pronounced osteoconductive, osteoinductive, and osteointegration properties. The work aims to evaluate the effect of calcium-phosphate ceramics doped with germanium on post-traumatic bone regeneration in conditions of secondary osteoporosis in rabbits. Experimental osteoporosis in rabbits was induced by administration of 0.4 % dexamethasone solution (KRKA, Slovenia) for 21 days at a dose of 1.2 mg/kg of body weight. Experimental (n = 9) and control (n = 9) groups of animals were formed. Animals of the experimental group had defects replaced with granules of hydroxyapatite ceramics, synthesized based on hydroxyapatite and β-tricalcium phosphate, doped with germanium. In rabbits of the control group, bone defects healed under a blood clot. Blood samples to determine the level of total calcium (Ca) and inorganic phosphorus (P) were taken before surgery and on 7-,14th, 30th, and 60th day of the study. X-ray studies were performed on the RUM-20 X-ray machine on the 14th, 30th, and 60th day of reparative osteogenesis. Radiologically and macromorphologically, it was established that reparative osteogenesis in the experimental animals proceeds more dynamically compared to the control group and is characterized by a high density of bone tissue at the site of the defect already on the 14th day after the injury, a moderate periosteal and early appearance of the endosteal reaction. The content of total calcium in the animals of the experimental group on the 14th day after the injury was 1.3 times (P < 0.001) higher than that of the control and animals before the operation, and on the 30th day, it was 1.2 times (P < 0.001) in accordance. The concentration of inorganic phosphorus (P) on the 14th and 30th days of reparative osteogenesis in animals of the experimental group was 1.1 times (P < 0.05) lower than in control animals, and on the 60th day in 1.4 times (P < 0.01), respectively. Systemic osteoporosis in experimental animals causes a violation of reparative osteogenesis due to the prolongation of the inflammatory-resorptive stage and cartilaginous callus and complicated mineralization of bone regeneration. Calcium-phosphate ceramics is a promising material for replacing bone defects in animals with systemic secondary osteoporosis.