Hydrolysis of Bone-Replacing Materials Based on Polylactic Acid and Containing Hydroxyapatite in an In Vitro Experiment.

We studied the features of hydrolytic degradation of polylactic acid (PLLA) implants depending on their structural filling with hydroxyapatite (HA). The resistance to in vitro hydrolysis was tested for the following samples: PLLA without HA (control; group 1), PLLA/HA 25 wt% (group 2), and PLLA/HA 50 wt% (group 3). Samples were incubated at 37°C. In the hydrolysate, lactate, calcium ions, and inorganic phosphate were determined. Additionally, the time of appearance of visual deformation and sample disintegration was recorded. PLLA degradation was higher in samples saturated with HA. The highest resistance to deformation was noted for samples without HA. Samples with a PLLA/HA 50 wt% demonstrated the maximum degradation of PLLA in combination with lower resistance to deformation and the highest bioavailability of calcium and phosphate. Group 2 samples are most promising for clinical use.

Solution blow spinning of PLLA/hydroxyapatite composite scaffolds for bone tissue engineering.

Composite poly-L-lactide acid-based scaffolds with hydroxyapatite (HAp) content up to 75 wt.% were fabricated via solution blow spinning. The influence of HAp concentration on structure, wettability, mechanical properties and chemical and phase composition of the produced materials was examined. It was found that with an increase of HAp content the average fiber diameter was increased, the uniaxial strength and relative elongation were reduced, while the phase composition and surface wettability did not change. The performance of the scaffolds during implantation in the parietal bone of a rat skull for a period from 15 to 90 days was studied. The materials have shown high ability to integrate with both soft and hard tissues. It was found that scaffolds with 25 wt.% HAp content significantly enhance osteogenesis during scarification (damage) of the periosteum. Overall, the fabricated scaffolds proved to be highly efficient for replacing bone defects in long tubular bones.

Bone Formation and Adaptive Morphology of the Anterior Tibial Muscle in 3-mm Daily Lengthening Using High-Fractional Automated Distraction and Osteosynthesis with the Ilizarov Apparatus Combined with Intramedullary Hydroxyapatite-Coated Wire.

PURPOSE: We studied osteogenesis and morphofunctional features of the anterior tibial muscle using 3-mm high-frequency automated lengthening with the Ilizarov apparatus alone and in combination with intramedullary nailing. MATERIAL AND METHODS: Tibia was lengthened with a round-the-clock automated distractor at a 3-mm daily rate for 10 days in 16 mongrel dogs. In group 1 (n = 8), a 1.8-mm intramedullary titanium wire coated with hydroxyapatite was introduced into the tibial canal followed by Ilizarov frame mounting and transverse osteotomy of the diaphysis. Distraction mode was 0.025 mm x 120 increments a day. In group 2 (n = 8), distraction mode was the same but nailing was not used. Bone formation and the anterior tibial muscle were studied at two time points: (1) upon distraction completion; (2) three months after the apparatus removal. Bone formation was studied radiographically. Muscle preparations were examined histologically and stereomicroscopically. RESULTS: There was a threefold reduction in the distraction time in both groups. Consolidation took 13.83±4.02 days in group 1 and 33.7±2.4 days in group 2. Muscle macropreparations of the experimental limb in group 1 at study time points did not show significant differences from intact tissues. Muscle histostructure in both groups was characterized by activation of angiogenesis and myohistogenesis, but the volumetric density of microvessels in the lengthening phase was three times higher in group 1. CONCLUSION: Combined technology significantly reduces the total lengthening procedure and does not compromise limb functions. Intramedullary HA-coated wires promote faster bone formation. The muscle was able to exhibit structural adaptation and plasticity of a restitution type.

Flexible intramedullary nails for limb lengthening: a comprehensive comparative study of three nails types.

This study aims to investigate the comparative study of calcium phosphate coatings for flexible intramedullary nails (FINs) used to lengthen long tubular bones. The presence of a calcium phosphate coating deposited by micro-arc oxidation (MAO) or a composite coating based on a co-polymer of vinylidene fluoride with tetrafluoroethylene (VDF-TeFE) and hydroxyapatite (HA) on the surface of the FIN significantly enhanced the regeneration of bone in the area of osteotomy during limb lengthening by combined osteosynthesis. The investigation of the physico-chemical properties of the FIN coated with calcium phosphate via MAO demonstrated that the improved bone tissue formation resulted from favourable conditions for adhesion, proliferation and differentiation of multipotent stem cells into osteoblasts on the coating surface. The composite coatings only stimulated the formation of bone tissue in vivo, primarily because of the piezoelectric properties of the VDF-TeFE co-polymer.

[GROWTH AND RESPONSE OF LEG TISSUES FOR TRANSPHYSEAL OSTEOSYNTHESIS OF TIBIAL SHAFT FRACTURE EXPERIMENTALLY].

Six (6) mongrel dogs at the age of six (6) months underwent transphyseal elastic intramedullary osteosynthesis for tibial shaft fracture. Clinical, X-ray, and physiological methods were used. As determined, the transphyseal reinforcement of the injured bone doesn't influence the lib function, but it retards the segment longitudinal growth. The eccentric arrangement of rods leads to forming angular deformity of the articular surface. Changes occur in the temperature of the covering tissues of the lateral tibial condyle. Consolidation period of the bone fragments is not increased. The union is formed through the blood flow of hypokinetic type in soft tissues. When intramedullary elastic rods being inserted the endosteal and periosteal response contributes to increasing the thickness of bone cortical plates and diameter.

[Intramedullary Elastic Transphyseal Tibial Osteosynthesis and Its Effect on Segmental Growth].

BACKGROUND: Intramedullary transphyseal elastic osteosynthesis is used in children for the diseases accompanied by the reduced strength properties of bone tissue, and primarily for osteogenesis imperfecta. OBJECTIVE: The purpose of the experimental study was to investigate tibial growth under the conditions of transphyseal counter-directed insertion of elastic rods without bone integrity breaking, under transverse fracture modeling, as well as under combining transphyseal reinforcement and subperiosteal positioning the titanium mesh with the elastic rods intervolved in it. METHODS: Non-randomized controlled trial was performed. Three series of experiments performed in 18 puppies. Counter-directed transphyseal reinforcement of tibia performed in Series I, transphyseal reinforcement combined with transverse osteotomy of leg bones--in Series II, transphyseal elastic osteosynthesis and subperiosteal positioning the titanium nickelide mesh with intervolved in it elastic rods during transverse leg bone osteotomy performed in Series III. RESULTS: Transphyseal reinforcement resulted in growth retardation of the operated tibia. The loss of residual growth was 3.8 mm (p=0.078) in series I; 7.8 mm (p=0.032)--in series II; 7.7 mm (p=0.042)--in series III. Eccentric insertion of transphyseal rods formed an angular deformity (mean value 7°; p=0.023) of the distal tibial epiphysis in the process of residual growth. Periosteal and endosteal reactions contributed to enlargement of diaphyseal diameter of 3.9 mm (series II; p=0.037) and 3.8 mm (series III; p=0.041). Any difference of diameter between operated and intact tibia was not observed in series I. CONCLUSION: Intramedullary transphyseal reinforcement retards longitudinal bone growth. The positioning of the telescopic systems should be as close as possible to the center of growth plates in order to prevent angular deformities. Subperiosteal reinforcement doesn't retard consolidation of fragments, and it can be combined with intramedullary transnhyseal osteosynthesis.

Bone healing by using Ilizarov external fixation combined with flexible intramedullary nailing versus Ilizarov external fixation alone in the repair of tibial shaft fractures: experimental study.

PURPOSE: Our research was aimed at studying the radiographic and histological outcomes of using flexible intramedullary nailing (FIN) combined with Ilizarov external fixation (IEF) versus Ilizarov external fixation alone on a canine model of an open tibial shaft fracture. MATERIALS AND METHODS: Transverse diaphyseal tibial fractures were modelled in twenty dogs. Fractures in the dogs of group 1 (n = 10) were stabilized with the Ilizarov apparatus while it was combined with FIN in group 2 (n = 10). RESULTS: On day 14, a bone tissue envelope started developing round the FIN wires. Histologically, we revealed only endosteal bone union in group 1 while in group 2 the radiographs revealed complete bone union on day 28. At the same time-point, the areas of cancellous and mature lamellar bone tissues were observed in the intermediary area in group 2. The periosteal layers were formed of the trabeculae net of lamellar structure and united the bone fragments. The frame was removed at 30 days after the fracture in group 2 and after 45 days in group 1 according to bone regeneration. CONCLUSION: The combination of the Ilizarov apparatus and FIN accelerates bone repair and augments stabilization of tibial shaft fractures as compared with the use of the Ilizarov fixation alone.

Blood circulation in muscles of the back in scoliosis deformity of the lumbar spine and under conditions of its correction.

Experiments performed on dogs showed that the formation of scoliotic deformity of the lumbar spine sharply affects the hemodynamics of the back muscles, which manifested in asymmetric arterial blood fl ow, increased blood supply to the tissues, and impaired venous outflow. The changes were more pronounced on the apex of epy developing deformity. Correction of scoliotic deformity gradually restored blood circulation in muscles of the back. The use of methods of functional diagnostic for evaluation of the status of blood circulation in the tissues of the back has diagnostic value and allows evaluation of the treatment efficiency.

Experimental study of progressive tibial lengthening in dogs using the Ilizarov technique. Comparison with and without associated intramedullary K-wires.

UNLABELLED: A delay in the union of bone regenerate in surgical lengthening procedures and the healing index (HI) are major factors in the quality of the results in progressive bone lengthening. Early removal of the external fixator (EF) is associated with a low rate of postoperative complications, including pin track infection, and with better muscle and joint function recovery. Addition of intramedullary wires (IMWs) to the EF led to a 9-49% decrease in the HI depending on the clinical series. We hypothesized that IMWs may accelerate the ossification process of bone regenerate and tested it in this experimental study. METHODS: Progressive tibial lengthening of 28 mm was obtained in 12 dogs operated with the classical Ilizarov technique (group I) and in 12 dogs operated with the same technique and addition of two IMWs 1.5 mm in diameter (group II). The following criteria were assessed: HI, X-ray measurements, and histological aspect of the bone regenerate and postoperative complications. RESULTS: The mean HI was 32.3% lower in group II than in group I. The radiological bone union criteria were observed on day 15 of the fixation period in group II versus day 30 in group I. Histology showed that maturation occurred earlier and bone cortices were thicker in group II than group I. Intramedullary ossification was present along the IMW in group II, whereas it was absent in group I. No clinical complications were observed in either group. DISCUSSION: The presence of the IMWs clearly contributes to stimulation of the ossification processes of the bone regenerate and to acceleration of bone union. IMWs allowed an earlier removal of the external fixator for a 32% time reduction compared to cases without IMWs. In addition, new intramedullary bone formation and presence of IMWs are expected to increase the mechanical resistance of the bone regenerate. CONCLUSION: Improvement of quantitative and qualitative criteria of bone regenerate in progressive bone lengthening with an EF combined with IMWs was demonstrated in this experimental study. SIGNIFICANCE: Favorable results encourage the authors to continue using IMWs in addition to the EF in patients treated with long-bone progressive lengthening. LEVEL OF EVIDENCE: II.

[Histomorphometric charactheristic of skeletal muscle regenerating after a closed partial crush injury].

To evaluate the degree of skeletal muscle regeneration in 15 adult Wistar rats, the closed partial crush injury of anterior tibial muscle was modeled. The study was performed using the methods of light microscopy and computer-assisted morphometry of semithin sections. The continuity of the crushed muscle fibres (MF) was restored by day 21 after the injury. After 90 days endomysial fibrosis was substantially reduced and its vasculairity increased; the variability of MF diameters was restored, however the branched structure and myopathic changes of the regenerated tissue persisted and were presumably associated with an incomplete reinnervation of the damaged intramuscular nerves.

[The effect of tibial transphyseal reinforcement on the growth and response of leg tissues].

Transphyseal reinforcement of right intact tibia performed with thin steel rods in six mongrel dogs at the age of six months. Contralateral segment served as control. The leg growth and blood supply studied under the created conditions for the next six months. Radiographic, physiologic (surface thermometry, photoplethysmography), and statistical methods used for studying. The significant effect of transphyseally inserted rods on the leg longitudinal growth and blood supply has not been revealed. The changes in natural shape-formation oftibial proximal and distal meta-epiphyses observed influenced by the transphyseal rods in the experiment. In order to evaluate the tissue response and the degree of the functional activity of leg bone meta-epiphyseal zones the most informative areas considered to be the following: the area of medial malleolus in the early period of physiological growth completion, and the area of the tibial lateral condyle--at the late stage.

Adaptation capacity of microcirculatory bed of the skin under conditions of high-frequency rate fractionated automated tibial elongation.

The status of the microcirculatory bed in the skin in the bone regenerate projection was studied under conditions of fractionated automated tibial elongation by transosteal distraction osteosynthesis at a rate of 3 mm/day in adult mongrel dogs. Histological and physiological data indicated that the distraction period was associated with changes in the functional components of the skin microcirculatory bed. Active neovasculogenesis and formation of additional arteriovenular anastomoses provided sufficient oxygenation of tissues and maintained venous outflow. This led to rapid recovery of the functional potentialities of skin microvessels as early as 1 month after the end of forced fixation.

[Blood circulation features by treatment of multiply mandible fractures by means of transosseus osteosynthesis].

The multiple injury of the mandible was modeled experimentally in 27 adult mongrel dogs with subsequent fixation using a device for transosseous osteosynthesis. The special features of soft tissue hemodynamics in the injury zone and contralateral symmetrical part were studied. It has been determined that the unidirectional changes in functional properties of the arterial bed vessels occur under the conditions created, and these changes are more marked on the injury side and characterized by vasodilatation. Circulation in the injury zone doesn't recover by the end of fixation. Performing the measures directed for the improvement of vascular elastotonic properties during mandibular fracture treatment will allow to decrease the degree of hemodynamics disorders in paraosseous tissues, as well as will have a positive effect on a final clinical outcome.

[Hemodynamics in soft tissues after upper third of the leg lengthening by Ilizarov osteosynthesis technique].

An experimental study has been performed. The leg was lengthened in 12 adult mongrel dogs by transosseous distraction osteosynthesis in the zone of upper third of the leg bone shaft by 14-18% of the segment length using the rate of 1.0 mm for 4 times. The formation of mechanically strong shaft part occurred after 35 days after device fixation. Under created conditions the unidirectional cyclic changes of blood circulation and morphofunctional state occurred in soft tissue segment, that were more marked in the extensor muscle group. Implementation of preventive-and-treatment measures directed to improvement of vascular elastotonic properties allowed to decrease the degree of disordering hemodynamics of the lengthened limb. This will have a positive effect on the final clinical outcome.