ABSTRACT
BACKGROUND: Plating ankle arthrodesis includes anterior and lateral plating methods, but there is some lack of knowledge about their differences in biomechanics. OBJECTIVE: To establish the three-dimensional models of anterior and lateral plating ankle arthrodesis through three-dimensional finite element technique, simulate human gait, and to analyze its biomechanical stability and safety. METHODS: The geometrical morphology of ankle joint was reconstructed based on the normal human ankle CT data. The models of anterior and lateral plating ankle arthrodesis were established using finite element analysis software Abaqus 2016, and the biomechanical changes after exerting stress at the positions of intorsion,extorsion, dorsiflexion, and neutral were analyzed. RESULTS AND CONCLUSION: (1) The maximal displacement and stress distribution under different stress were compared between two models by three-dimensional element analysis, and there was no significant difference in the stability between two models. (2) The abilities of resistance to intorsion and dorsiflexion stresses of the lateral plating model were slightly better than those of the anterior plating model, but the resistance to extorsion stress of the lateral plating model was lower than that of the anterior plating model; the stress peak both concentrated on the plate-screw connections. (3) The plate, screw and bone mass of the anterior plating model showed the maximum stress peak under intorsion stress, and broken plates and nails usually occur. (4) The lateral plating presented with peak stress under extorsion stress.
ABSTRACT
BACKGROUND:Previous studies have shown that traumatic brain injury can promote the regeneration of peripheral nerve by reducing scar collagen in nerve endings.OBJECTIVE:To investigate the effect of brain injury at different locations on the ipsilateral rat sciatic nerve regeneration.METHODS:Ninety-nine healthy male Sprague-Dawley rats were equivalently randomized into three groups:group A,right sciatic nerve transection;group B,right sciatic nerve transection combined with right brain injury;and group C,right sciatic nerve transection combined with left brain injury.All of transected nerves were sutured under microscope.Classical Feeney method was used to establish a model of traumatic brain injury.At 4,6,8,10 and 12 weeks after modeling,the sciatic functional index (SFI) was calculated by measuring footprint.At 4,8 and 12 weeks after modeling,the bilateral gastrocnemius were harvested for determining wet weight and calculate wet weight ratio,followed by acetylcholinesterase staining at the motor end plate to detect the absorbance values.At 4,8 and 12 weeks after modeling,fluoro-gold retrograde tracing was used to trace L4-5 vertebrae for 1 week,and the number of spinal cord anterior horn motor neurons positive for fluoro-gold was detected and calculated by fluorescence microscope.RESULTS AND CONCLUSION:The SFI value in each group was gradually improved with time.The SFI value was significantly higher in the groups B and C than the group A at 4 and 6 weeks after modeling (P ＜ 0.05),and was further improved in the group B at 8 weeks compared with the groups A and C (P ＜ 0.05).The wet weight ratio of gastrocnemius showed no significant difference among groups at 4 weeks after modeling (P ＞ 0.05),and the group B showed a significantly higher wet weight ratio than the other groups from the 8th week (P ＜ 0.05).Compared with the groups A and C,the absorbance values of motor endplate in group B appeared to be a significant increase at the beginning of the 8th week (P ＜ 0.05).At 4 and 6 weeks after modeling,the number of spinal cord anterior horn motor neurons positive for fluoro-gold was significantly nigher in the groups B and C than in the group A,and the number was significantly higher in the group B than the groups A and C at 12 weeks (all P ＜ 0.05).These finding manifest that brain injury can promote the repair of ipsilateral sciatic nerve injury,thus proving theoretical reference for unveiling the mechanism by which traumatic brain injury promotes peripheral nerve regeneration.
ABSTRACT
<p><b>OBJECTIVE</b>To determine the effect of activation of lambda-opioid receptor with U50, 488H, a selective kappa-opioid receptor agonist, on the changes in electrical coupling during prolonged ischemia and to explore the possible mechanism.</p><p><b>METHODS</b>The isolated rat heart was perfused in a Langendorff apparatus. The effect of U50, 488H on electrical coupling parameters including onset of uncoupling, plateau time, slope and fold increase in r(t) was observed in isolated perfused rat heart subjected to global no-flow ischemia. The effect of U50, 488H on connexin 43 (Cx43) expression of ventricular muscle during ischemia was determined by immunohistochemistry.</p><p><b>RESULTS</b>In the prolonged ischemia model, U50, 488H concentration dependently delayed the onset of uncoupling, increased time to plateau, and decreased the maximal rate of uncoupling during ischemia. The effect of U50, 488H on electrical uncoupling parameters during ischemia was abolished by a selective kappa-opioid receptor antagonist nor-BNI or a PKC inhibitor chelerythrine. The amount of Cx43 immunoreactive signal in ventricular muscle was greatly reduced after ischemia. U50, 488H markedly increased Cx43 expression during ischemia and its effect was also attenuated by nor-BNI or chelerythrine.</p><p><b>CONCLUSION</b>These results demonstrated that U50, 488H delayed the onset of uncoupling and plateau time, decreased the maximal rate of uncoupling and increased Cx43 expression of ventricular muscle during ischemia, and these effects of U50, 488H were mediated by kappa-opioid receptor, in which activation of PKC was involved. The effect of U50, 488H on electrical coupling during ischemia was probably correlated with preservation of Cx43 in cardiac muscle.</p>