Photobiomodulation in Sciatic Nerve Crush Injuries in Rodents: A Systematic Review of the Literature and Perspectives for Clinical Treatment

Introduction: The aim of the study was to perform a literature review to analyze the effect of photobiomodulation in experimental studies on peripheral nerve regeneration after sciatic nerve crush injury in rodents.Methods: A bibliographic search was performed in the electronic databases, including MEDLINE (PubMed), SCOPUS, and SciELO, from 2008 to 2018.Results: A total of 1912 articles were identified in the search, and only 19 fulfilled all the inclusion criteria. Along with the parameters most found in the manuscripts, the most used wavelengths were 660 nm and 830 nm, power of 30 and 40 mW, and energy density of 4 and 10 J/cm2. For total energy throughout the intervention period, the lowest energy found with positive effects was 0.70 J, and the highest 1.141 J. Seventeen studies reported positive effects on nerve regeneration. The variables selected to analyze the effect were: Sciatic Functional Index (SFI), Static Sciatic Index (SSI), morphometric, morphological, histological, zymographic, electrophysiological, resistance mechanics and range of motion (ROM). The variety of parameters used in the studies demonstrated that there is yet no pre-determined protocol for treating peripheral nerve regeneration. Only two studies by different authors used the same power, energy density, beam area, and power density.Conclusion: It was concluded that the therapeutic window of the photobiomodulation presents a high variability of parameters with the wavelength (632.8 to 940 nm), power (5 to 170 mW) and energy density (3 to 280 J /cm2), promoting nerve regeneration through the expression of cytokines and growth factors that aid in modulating the inflammatory process, improving morphological aspects, restoring the functionality to the animals in a brief period.Keywords: Phototherapy; Nerve regeneration; Sciatic nerve; Experimental studies; Injury; Lasers and light sources

Photobiomodulation: evaluation of scattering, transmission, and their biological effects in healthy individuals

Uma das limitações da fotobiomodulação é a geração da potência pelos equipamentos e a consequente fluência fornecida aos tecidos, associada as características ópticas da pele, o que implica na profundidade de penetração in vivo. Clinicamente, a literatura aponta melhora no desempenho muscular associado a fotobiomodulação. Entretanto, há uma lacuna entre os parâmetros físicos da fotobiomodulação e o desempenho muscular. A presente tese, dividida em três estudos, avalia a fotobiomodulação quanto a potência, espalhamento, transmissividade e seus efeitos biológicos em indivíduos saudáveis. Estudo 1 - Avaliar a potência e o diâmetro do feixe dos lasers de baixa potência. Foram avaliados vinte e quatro equipamentos com um tempo médio de aquisição de 11 ± 5 anos, com um uso semanal médio inferior a trinta minutos. Os resultados demonstram variações da potência entre 2% a 134% e de 38% e 543% no diâmetro do feixe frente os valores declarados. Destaca-se que, mesmo entre a mesma marca e modelo, foram obtidas diferenças de diâmetro. Finalmente, foram observadas diferenças na potência de saída após um e três minutos de emissão sequencial para 830 nm e 904 nm (p<0,05), mas não ao comparar a diferença entre os comprimentos de onda no fator tempo. Estudo 2 - Analisar a influência da melanina na transmissão e espalhamento do laser 660 nm e 830 nm na pele e tendão in vivo. Trinta indivíduos jovens de ambos os sexos foram recrutados, divididos em dois grupos com base na concentração de melanina e submetidos a protocolos de fotobiomodulação na região posterior do cotovelo (pele-pele) e no tendão do calcâneo (pele-tendão-pele). A área de irradiação foi avaliada usando uma matriz linear de cinco sensores. Foram encontrados valores inferiores de potência transmitida para maiores índices de melanina e menores comprimentos de onda (p<0,05). A dispersão do feixe para 660 nm foi de 14 mm e 21 mm e para 830 mm foi de 20 mm e 26 mm, considerando os maiores e menores índices de melanina, respectivamente. Estudo 3 - Analisar os efeitos do treinamento associado a fotobiomodulação nas capacidades de força, atividade metabólica e escalas clínicas em indivíduos saudáveis. Cinquenta e seis participantes do sexo masculino foram divididos em quatro grupos (Sham, 60 J, 300 J e Incremental) que, após avaliação da composição corporal e dinamometria isocinética, executaram dez sessões de treinos associado a aplicação de fotobiomodulação prévia. Não foram observadas diferenças significativas (p<0,05) entre os grupos para os índices da dinamometria isocinética, com pequenos a moderados efeitos a favor da dose incremental e máxima, sendo observados os mesmos desfechos para demanda psicofisiológica do exercício ou a carga. Como conclusão geral, há necessidade de um esforço compartilhado por parte dos fabricantes dos equipamentos e operadores, tanto para melhorar a padronização e a consistência dos equipamentos, quanto para manutenção e monitoramento do desempenho ao longo do tempo. Frente as individualidades, a transmissão da luz laser in vivo está relacionada ao comprimento de onda, diâmetro do feixe, espessura, composição do tecido e ao índice de concentração de melanina. Finalmente, a terapia de fotobiomodulação associada ao protocolo de treinamento não promoveu resultados superiores para capacidade muscular, índices psicofisiológicos e metabólicos entre os diferentes grupos avaliados.One of the limitations of photobiomodulation is the generation of power by the equipment and the consequent fluence delivered to the tissues, associated with the optical characteristics of the skin, which implies the depth of penetration in vivo. Clinically, the literature points to an improvement in muscle performance associated with photobiomodulation. However, there is a gap between the physical parameters of photobiomodulation and muscle performance. The present thesis, divided into three studies, evaluates photobiomodulation in terms of power, scattering, transmissivity, and biological effects in healthy individuals. Study 1 - To evaluate the power and beam diameter of low-level lasers. Twenty-four devices were evaluated, with a mean acquisition time of 11 ± 5 years, with a mean weekly use of fewer than thirty minutes. The results show variations in power from 2% to 134% and from 38% to 543% in beam diameter compared to the declared values. It is noteworthy that differences in diameter were obtained even among the same brand and model. Finally, differences were observed in output power after one and three minutes of sequential emission for 830 nm and 904 nm (p<0.05), but not when comparing the difference between wavelengths in the time factor. Study 2 - To analyze the influence of melanin on the transmission and scattering of the 660 nm and 830 nm laser on skin and tendon in vivo. Thirty young individuals of both sexes were recruited, divided into two groups based on melanin concentration, and subjected to photobiomodulation protocols on the posterior elbow (skin-skin) and calcaneus tendon (skin-tendon-skin). The irradiation area was evaluated using a linear array of five sensors. Lower transmitted power values were found for higher melanin indices and shorter wavelengths (p<0.05). The beam scatter for 660 nm was 14 mm and 21 mm and for 830 mm was 20 mm and 26 mm, considering the highest and lowest melanin indices, respectively. Study 3 - To analyze the effects of training associated with photobiomodulation on strength capabilities, metabolic activity, and clinical scales in healthy individuals. Fifty-six male participants were divided into four groups (Sham, 60 J, 300 J, and Incremental) that, after body composition and isokinetic dynamometry evaluation, executed ten training sessions associated with the application of photobiomodulation. No significant differences (p<0.05) were observed between the groups for the isokinetic dynamometry indexes, with small to moderate effects in favor of the incremental and maximum doses. The same outcomes were observed for the psychophysiological demand of the exercise or the load. As a general conclusion, there is a need for a shared effort by equipment manufacturers and operators to improve the standardization and consistency of the equipment and maintain and monitor performance over time. Faced with individualities, laser light transmission in vivo is related to wavelength, beam diameter, thickness, tissue composition, and the melanin concentration index. Finally, photobiomodulation therapy associated with the training protocol did not promote superior muscle capacity and psychophysiological and metabolic indexes among the different groups evaluated

Correlation between skin temperature in the lower limbs and biochemical marker, performance data, and clinical recovery scales.

The aim of this study was to evaluate the correlation between tools commonly used in the detection of physiological changes, such as clinical complaints, a biochemical marker of muscle injury, and performance data during official matches, with infrared thermography, which has been commonly used in the possible tracking of musculoskeletal injuries in athletes. Twenty-two athletes from a professional soccer club (age 27.7 ± 3.93 years; BMI 24.35 ± 1.80 kg/cm2) were followed during the season of a national championship, totaling 19 matches with an interval of 7 days between matches. At each match, the athletes used a Global Positioning System (GPS) device to collect performance data. Forty-eight hours after each match, every athlete's perception of recovery, fatigue, and pain was documented. Blood was collected for creatine kinase (CK) analysis, and infrared thermography was applied. Only athletes who presented pain above 4 in either limb were included for thermographic analysis. Each thermographic image was divided into 14 regions of interest. For statistical analysis, we included only the images that showed differences ≥ 1° C. Data normality was verified by the Kolmogorov-Smirnov test with Dallal-Wilkinson-Lilliefors correction. We used the Pearson correlation coefficient to verify the correlation between infrared thermography and the biochemical marker, performance data, and clinical recovery scales. No correlation was observed between mean skin temperature and blood CK levels, pain level, perception of recovery, and fatigue perception (r 0.05). Thus, infrared thermography did not correlate with CK level, pain, fatigue perception, or recovery, nor with performance variables within the field

Evolution of Skin Temperature after the Application of Compressive Forces on Tendon, Muscle and Myofascial Trigger Point.

Some assessment and diagnosis methods require palpation or the application of certain forces on the skin, which affects the structures beneath, we highlight the importance of defining possible influences on skin temperature as a result of this physical contact. Thus, the aim of the present study is to determine the ideal time for performing thermographic examination after palpation based on the assessment of skin temperature evolution. Randomized and crossover study carried out with 15 computer-user volunteers of both genders, between 18 and 45 years of age, who were submitted to compressive forces of 0, 1, 2 and 3 kg/cm2 for 30 seconds with a washout period of 48 hours using a portable digital dynamometer. Compressive forces were applied on the following spots on the dominant upper limb: myofascial trigger point in the levator scapulae, biceps brachii muscle and palmaris longus tendon. Volunteers were examined by means of infrared thermography before and after the application of compressive forces (15, 30, 45 and 60 minutes). In most comparisons made over time, a significant decrease was observed 30, 45 and 60 minutes after the application of compressive forces (p < 0.05) on the palmaris longus tendon and biceps brachii muscle. However, no difference was observed when comparing the different compressive forces (p > 0.05). In conclusion, infrared thermography can be used after assessment or diagnosis methods focused on the application of forces on tendons and muscles, provided the procedure is performed 15 minutes after contact with the skin. Regarding to the myofascial trigger point, the thermographic examination can be performed within 60 minutes after the contact with the skin

Photograph and infrared image of the palmaris longus tendon (A and D), biceps brachii muscle (B and E) and active myofascial trigger point in the insertion of the levator scapulae (C and F).

<p>Photograph and infrared image of the palmaris longus tendon (A and D), biceps brachii muscle (B and E) and active myofascial trigger point in the insertion of the levator scapulae (C and F).</p

Comparison of the skin temperature (degrees Celsius) on biceps the brachii muscle over time and at different compressive forces.

<p>Values shown in mean (95% confidence interval). All comparisons were made by means of two-way repeated measures analysis of variance post hoc Bonferroni. P0: Before the application of compressive force; P15: Fifteen minutes after; P30: Thirty minutes after; P45: Forty-five minutes after; P60: Sixty minutes after.</p><p>^aDiffers significantly from P60 (p < 0.05)</p><p>^bDiffers significantly from P45 (p < 0.05)</p><p>^cDiffers significantly from P30 (p < 0.05).</p><p>Comparison of the skin temperature (degrees Celsius) on biceps the brachii muscle over time and at different compressive forces.</p

Comparison of the skin temperature (in degrees Celsius) on myofascial trigger point over time and at different compressive forces.

<p>Values shown in mean (95% confidence interval). All comparisons were made by means of two-way repeated measures analysis of variance post hoc Bonferroni. P0: Before the application of compressive force; P15: Fifteen minutes after; P30: Thirty minutes after; P45: Forty-five minutes after; P60: Sixty minutes after.</p><p>No significant differences in comparisons over time or between different compressive forces (p > 0.05).</p><p>Comparison of the skin temperature (in degrees Celsius) on myofascial trigger point over time and at different compressive forces.</p