Influence of different methods of internal bone fixation on characteristics of bone callus in experimental animals

Introduction. Correct choice of osteosynthesis method is a very important factor in providing the optimal conditions for appropriate healing of the fracture. There are still disagreements about the method of stabilization of some long bone fractures. Critically observed, no method of fracture fixation is ideal. Each osteosynthesis method has both advantages and weaknesses. Objective. The objective of this study was to compare the results of the experimental application of three different internal fixation methods: plate fixation, intramedullary nail fixation and self-dynamisable internal fixator (SIF). Methods. A series of 30 animals were used (Lepus cuniculus) as experimental animals, divided into three groups of ten animals each. Femoral diaphysis of each animal was osteotomized and fixed with one of three implants. Ten weeks later all animals were sacrificed and each specimen underwent histological and biomechanical testing. Results. Histology showed that the healing process with SIF was more complete and bone callus was more mature in comparison to other two methods. During biomechanical investigation (computerized bending stress test), it was documented with high statistical significance that using SIF led to stronger healing ten weeks after the operation. Conclusion. According to the results obtained in this study, it can be concluded that SIF is a suitable method for fracture treatment

Joined statistical – thermodynamic expression for entropy and Hook’s law in the analysis of states of elongated ligament biostructure

Analytic joined statistical - thermodynamic expression for entropy as a function of state for measuring disorder of the corresponding micro state and the mechanical parameters which feature in Hooke’s law on elasticity as a measure of macro state was used in the situation of isothermal elongation of viscoelastic ligament biostructure simultaneously with external force of constant intensity to determine the change of entropy and the resultant reactive elastic force in the function of relative elongation. The sample used for the analysis and testing of the original joined theory shown with adequate equations is tested on linear biostructure approximating the data of Lig. collatelare fibulare which strengthens the lateral side of the knee joint. The obtained results for the tested linear biostructure according to which the minimal value of the difference in dS corresponds to the state of maximal entropy and the minimal value of elastic force indicates the acceptable level of elongation at which a reversible process is still possible, with low probability. This leads to the conclusion that, according to the results obtained here, the biostructure under examination can withstand the elongation which is approximately equal to twice the initial length L0. The relation between the friction force Ftr and the elasticity force Fe for the initial state is 1.0417, which indicates that the friction force is to a certain extent higher than the elastic force. With elongation this ratio changes in favour of the friction force and becomes more prominent with advanced age