Effect of ascorbic acid and epidermal growth factor in a rat tibia defect

Purpose: Bone repair aims to restore the anatomical, biomechanical, and functional integrity of the affected structure. Here we study the effects of ascorbic acid (AA) and epidermal growth factor (EGF) applied in a single dose and in combination on the repair of a noncritical bone defect model. Methods: Twenty-four rats were divided into four groups: an intact G-1 control group, and three groups that underwent a noncritical bone defect in the right tibia: G-2 treated with AA, G-3 treated with EGF, and G-4 treated with AA in combination with EGF. After 21 days of treatment, rats were sacrificed, the tibias were dissected and a destructive biomechanical analysis of three-point flexion test was performed in a universal testing machine; the values of stiffness, resistance, maximum energy, and energy at maximum load were statistically compared. Results: G-3 and G-4 recovered the biomechanical properties of strength and stiffness of an intact tibia 3 weeks after their application. Not so the energy and energy at maximum load. For G-2, only the stiffness of an intact tibia was recovered. Conclusion: EGF and AA-EGF applied to a noncritical bone defect in the rat tibia favors the recovery of bone resistance and stiffness.

Tensiometric evaluation of the effect of low frequency electric stimulation on healing Achilles tendons in rats

Purpose: To evaluate the effects of low-frequency electric stimulation on biomechanics following surgical treatment of the Achilles tendon in rats. Methods: Forty-two rats were divided into two groups. One was given electric stimulation and the other was not. All were submitted to Achilles tenotomy and tenorrhaphy performed with a modified Kessler stitch. The experiment group underwent electric stimulation with 2 Hz, a nonpolarized current of 1 mA intensity for 14 days. The animals were euthanized at 2, 4 and 6 weeks for the biomechanical study. Results: The work performed, that is, the tendons capacity to absorb energy until rupture, was greater in the electrically stimulated group in the 2nd (p = 0.032) and in the 6th week (p = 0.010). The maximum tension, which is the capacity to support a load, was higher in the treated group in the 2nd (p = 0.030) and the 6th week (p = 024). These results indicate greater resistance of the electrically stimulated tendons. An analysis of the elastic module showed no differences. Conclusion: Low-frequency electric stimulation increased the resistance of the tendons at 2 and 6 weeks of evolution in rats.(AU)

Propriedades biomecânicas de ossos longos de coelhos: correlação com medidas de absorciometria de raios-x de dupla energia

Nosso objetivo aqui era fornecer uma caracterização macroscópica e biomecânica sistemática do tecido ósseo coletado dos ossos longos (femora, tíbia e úmero) de trinta coelhos fêmeas da Nova Zelândia (Oryctolagus cuniculus) da Nova Zelândia, remanescentes de um experimento de pesquisa anterior de um instituição parceira que seria desperdiçada de outra forma. Após requerer permissão ética de todas as instituições envolvidas neste estudo, colhemos os ossos longos (fêmur, tíbia e úmero) e dissecamos-os dos tecidos moles com dissecção contundente, removendo também a camada periosteal. Nós os avaliamos radiograficamente para excluir amostras de ossos com anormalidades prévias ou sem fechamento epifisial. Registramos suas medidas morfológicas básicas e avaliamos os valores de massa óssea e conteúdo mineral por meio de exames de absorciometria por raios-X de dupla energia. Dividimos os 30 coelhos em três grupos (n = 10 coelhos ou 60 amostras ósseas cada), de acordo com o tipo de teste biomecânico a que seriam submetidos: compressão axial, flexão de três pontos e torção. Ossos do mesmo coelho foram submetidos à mesma modalidade de teste. Determinamos os valores normais e comparamos diferenças da esquerda para a direita e possíveis correlações com a massa óssea. Utilizou-se o software livre R para análises estatísticas, utilizando e definido a equivalência estatística em p> 0,05. Realizamos um teste de normalidade Shapiro-Wilk para confirmar a homogeneidade das variações. Em seguida, aplicamos um teste de Student emparelhado nos dados normalmente distribuídos e o teste de Wilcoxon para aqueles que não são normalmente distribuídos. Avaliamos possíveis correlações entre dados paramétricos em relação à resistência óssea e massa óssea com um teste de correlação de Pearson; caso contrário, aplicamos o teste de correlação de Spearman. Encontramos apenas uma diferença significativa da direita para a esquerda na rigidez compressiva diafisária das tíbias, provavelmente devido a erros no método de preparação manual. Conseguimos não apenas impedir o desperdício de material biológico viável, minimizando o sofrimento dos animais (de acordo com o conceito 3 "Rs"), mas também fortalecendo os laços interdisciplinares e criando novos caminhos de pesquisa multicêntrica que vão além da instituição local. Esse objetivo está de acordo com o objetivo da universidade de treinar estudantes autônomos e qualificados, que podem se destacar no aprendizado, ensino e promoção de pesquisas que ultrapassam os limites de seu próprio campo de conhecimento.

Our purpose here was to provide a systematic macroscopic and biomechanical characterization of the osseous tissue collected from the long bones (paired femora, tibiae and humeri) of thirty New Zealand white female rabbits (Oryctolagus cuniculus) cadavers, remnants of a previous research experiment of a partner institution that would be wasted otherwise. After requiring ethical permission from all the institutions involved in this study, we harvested their long bones (femora, tibiae and humeri) and dissected them free of soft tissues with blunt dissection, removing the periosteal layer as well. We radiographically assessed them to exclude any bone samples with previous abnormalities or lacking epiphysial closure. We recorded their basic morphological measurements and assessed values of bone mass and mineral content by dual-energy x-ray absorptiometry exams. We divided the 30 rabbits into three groups (n=10 rabbits or 60 bone samples each), according to the type of biomechanical test they would be subjected to: axial compression, three-point bending and torsion. Bones from the same rabbit underwent the same testing modality. We determined normal range values and compared left-to-right differences and possible correlations to bone mass. We used the free software R for statistical analyses using and set statistical equivalence at p > 0.05. We performed a Shapiro-Wilk normality test to confirm the homogeneity of the variations. Then we applied a paired Student test on the normally distributed data and the Wilcoxon test for those not normally distributed. We assessed any possible correlations between parametric data regarding bone resistance and bone mass with a Pearsons correlation test, otherwise we applied the Spearmans correlation test. We only encountered a significant right to left difference in the diaphyseal compressive stiffness of tibiae probably due to errors in the manual preparation method. We succeeded not only on preventing the waste of viable biological material whilst minimizing animal suffering of animals (according to the 3 "Rs" concept), but also in strengthening interdisciplinary bonds and creating new multicentric research pathways that goes beyond the local institution. That goal resonates to the universitys purpose to train autonomous and qualified students who can excel at learning, teaching and promote research outstanding the limits of their own field of knowledge.