Socrates Almanac

1

Authors: Panchenko Tatiana Yurievna

It is generally believed that chronical infections of mucous coat and skin in most cases occur under some quantitative deviations of key cell parameter of immune system and (or) functional insufficiency of separate cells. For example, hemophage. It was established in previous works that local immunity factors in earwax are defined rather distinctly and in some cases their quantitative deviations are associated with clinical manifestations of external otitis. Along with that, information on the immunity factors state at recurrent external otitis is not enough to define the roles of different chains of immune system in pathogenesis of external otitis. For the purpose of expanding the understanding of the external otitis pathogenesis factors and establishment of effective approach to treatment order we studied the state of some system factors of immunity in peripheral blood at patients with external otitis in remission and in process recrudescence.

19

Authors: Prof. Oleg Vyrva, M.D.

Introduction: Implant failure is the most frequent complication after sur-gery for large bone defect. Mathematical modelling and finite element method allow and show the mechanical features of the interaction between femoral bone and endoprosthesis after distal femur replacement. The stressedly-deformed condition of the distal femur endoprosthesis depends on the angle of inclination and the length of intramedullary stem and the level of the femoral bone resection. Material and method(s): The finite element method for three-dimensional model of the femur was used. This model was created in the form of 3D object with the reconstitution of anatomical features of the proximal and distal ends of femoral bone. The prototype was the teaching specimen as a freeze-dried native male right femur. The model reproduces of anatomic features of the bone shaft - back crista and antecurvation. There are two parts: the first one (external) had mechanical properties of cortical bone, the second one (internal) had characteristics of trabecular bone and had form of a hollow rod. For further studies distal end of the femur model was removed and bone defect was replaced by implant. Three variants of the model have been developed to study the mechanical features of implant-femur interaction. The models reproduced bone defect replacement by implants with different values of inclination angle between the upper and middle parts of the implant. Investigation of the stressedly-deformed condition was realized under load bearing with 0°, 30°, 60° and 90° of the inclination angles between hip and knee joints load lines. Intramedullary stem lengths were 80, 110 and 140 mm and the lengths of prosthesis body were 96, 196 and 296 mm as well. Result(s) and Conclusion(s): Maximum stresses arise in the intramedullary stem along its entire length and load peak is localized in the base of intramedullary stem. The bone resection stress concentration is observed in 5° inclination angle of intramedullary stem and the endoprosthesis body. The angle between implant body and stem has to be selected individually in the range from 1 to 4 degrees for optimum performance. Stress rate is inversely proportional to the stem lenght. Stress rate is observed in great trochanter zone when the end of the intramedullary stem is in intertrochanteric area. The prosthesis stem should not be shorter than 100 mm. The end of it should not be placed in the intertrochanteric area. Significant increase stress rates in intramedullary stem and femoral shaft are observed with the distal third resection of the femoral bone. Zone of maximum stress rates moves from bone shaft to prosthesis body when level of femur resection is on upper and middle thirds of it. It drives to the overall reduction of stress rates regardless of weigh bearing angle of knee joint.