The Effect of Laser Irradiation on Reparative Osteogenesis

Introduction: The use of non-medicinal facilities for correcting processes in various pathological conditions is one of the most urgent problems of modern medicine. Purpose of the Work: To study the effect of low-intensity infrared laser radiation on reparative bone formation and angiogenesis in bone regeneration which is formed in treatment of fractures under conditions of transosseous osteosynthesis. Material and Methods: A tibia fracture was modeled experimentally in rats in the control and experimental groups. Reposition and fixation of fragments were performed. The fracture zone in the experimental group animals was exposed to the impact of pulsed infrared laser irradiation of low intensity. Animals from the control group underwent the impact simulation. The operated bones were investigated using the methods of X-ray, light and electron microscopy, X-ray electron probe microanalysis. Results: It was established that laser radiation exposure sessions activated fibrillogenesis and angiogenesis, accelerated compacting of newly formed bone tissue and increased its maturity while primary fracture healing occurred. Prolonged capillary dilatation and endothelium-dependent vasodilation, intensive capillarogenesis were noted after sessions of laser therapy in bone regeneration. Endothelial outgrowth was formed in the lumen of the vessels forming capillary buds that propagate along the “mother” vessels (endovascular capillarogenesis). Conclusion: The data obtained revealed a possible mechanism of laser radiation exposure at the level of a whole organism and proved the effectiveness of its application in clinical practice at the early stages of patient rehabilitation under conditions of transosseous osteosynthesis. Corresponding author: N. A. Kiryanov,Russian, Izhevsk State Medical Academy, Russia, E-mail: kirnik@list.ru


Introduction
The use of non-medicinal facilities for correcting reparative regeneration processes in various pathological conditions is one of the most urgent problems in modern medicine. Laser therapy of different types is widely used in clinical practice including traumatology and orthopaedics for treating locomotorium injuries and diseases. It is aimed to provide anesthetizing, anti-edematous, anti-inflammatory and trophic-stimulating effects [1,2,3,4,5]. It also ensures the decrease in medicinal burden in a patient's organism. The treatment with laser beams is comfortable, non-invasive, aseptic, painless, harmless, and controllable [67, 8,9,10,11]. The low-energy laser impact has a multifactorial effect on the organism [12,13,14,15,16]. The activity of the enzymatic systems and the rate of oxygen consumption by tissues increase, the level of peroxide lipid oxidation decreases, oxidation-restoration processes activate, and the concentration of adaptive hormones increases [17,18,19]. At the same time the mechanism of laser therapeutic impact is largely unclear, and the doses are selected empirically. There is little experimental work in this area and it is mainly performed by X-ray and clinical methods [20,21]. There is no information on the efficacy of low-intensity infrared laser radiation in treatment of fractures under conditions of transosseous osteosynthesis and its influence on morphological features of bone regeneration. It indicates the urgency of the problem and the need for its study.
The purpose of this work is to study the effect of lowintensity infrared laser radiation on reparative bone formation and angiogenesis in bone regeneration which is formed in treatment of fractures under conditions of transosseous osteosynthesis.

Material and Methods
The experimental procedure

Methods of a Statistical Analysis
The results of quantitative investigations were processed by variation statistics methods. The significance of differences in the compared parameters was calculated using Student t-test. Differences were considered to be significant for the level of р < 0.05.

Results
A transverse fracture in the middle third of the tibial shaft diaphysis was determined in animals 7 days after the operation (Fig. 1). Edges of the fragments had uneven surfaces. There was no bone fusion in the animals of the control group (Fig. 1a). Volumetric periosteal and endosteal bone-osteoid stratifications grew into the regeneration on the bone fragments ends from the periosteal and endostea surfaces and overlapped diastase (Fig. 1b, Fig. 3). Bone fusion between fragments was formed (intermediate regeneration). The calcium content in this zone was 15-20 % (Fig. 3a). Numerous blood vessels and cells at various stages of osteogenic differentiation were located between the bony beams ( Fig. 3b, 3c, 4a).  (Fig. 4c, 4d). It indicated active processes of reparative angiogenesis. Endovasal endothelial processes had a characteristic tile-like outer layer which had been formed by flat marginal regions of neighboring endotheliocytes (Fig. 4c).

Discussion
Clinical and experimental-morphological studies by Academician G.A. Ilizarov and his students [26,27] proved Stimulation of the endothelial outgrowths formation in the lumen of the vessels forms the capillary buds. They propagate along the "mother" vessels for considerable distances not meeting the resistance of perivascular tissue structures. This method of formation and capillary growth directly in the lumen of pre-existing vessels is called "endovasal capillarogenesis". It was first described by us in the study of bone wound healing [28][29][30][31][32][33]. It is one of the stages of regenerative angiogenesis and provides accelerated regeneration and oriented growth of newly formed vessels.

Conclusion
The findings revealed a possible mechanism of the laser irradiation impact at the level of the whole organism. They confirm the efficiency of its use in clinical practice at the early stage of the patient rehabilitation under transosseous osteosynthesis.

Acknowledgement
We are thankful to the staff of our institutions for the assistance in carrying out the experiments and care for the animals at all the stages of our work.