Treatment of hip pathology has evolved over the last two centuries, ranging from rudimentary surgical procedures to modern hip arthroplasty, with an explosion marked in the last 30 years, considered to be one of the most successful surgeries to date. Hip arthroplasty is a permanent challenge due to the desire to discover the "supreme prosthesis", for which competition is still open. Hip disorders requiring prosthesis show a change in articular morphology. Among the most common medical conditions that have as final therapeutic solution hip arthroplasty are: coxarthrosis, both primary and secondary, followed by traumatic conditions: femoral neck collapse and femoral neck pseudarthrosis, aseptic head necrosis femoral stage III, as well as rheumatic coxitis from rheumatoid arthritis, ankylosing spondylitis or juvenile art. Endoprosthetic arthroplasty can be defined as an intervention of reconstructive surgery with bone sacrifice and prosthetic replacement of the articular components. It is, in the end, an operation aimed at restoring joint mobility and normal functioning of the muscles, ligaments and other periarticular structures that control joint movement. The materials initially used (glass, metal, plastic) did not have the desired bone strength and integration capacity. It followed the development of cemented implants, obtaining different types of cement with better and better quality. Problems arising from cemented arthroplasty (decimation, involving prosthetic revision) have led to a parallel development of the design and materials used for uncured prostheses with the possibility of very good integration of prosthetic material into the bone, raising them to the top of preferences in recent years. Treatment of hip pathology has evolved over the last two centuries, ranging from rudimentary surgical procedures to modern hip arthroplasty, with an explosion marked in the last 30 years, considered to be one of the most successful surgeries to date. The purpose of this study was to obtain the three-dimensional models of the hip joint and the prosthesis for the use of these models for various analyzes and virtual experiments. At the end of the paper important conclusions were drawn based on the results obtained in the simulations using the finite element method.
This paper presents an experimental study of the flexion-extension movement of the human lower limb joints. Measurements were performed on a group of fourteen healthy subjects, experimental data being obtained for flexion-extension cycles during five different walking tests on horizontal and inclined treadmills. Experimental data were obtained using the Biometrics system, which is based on electrogonimeter sensors. Average cycles for each joint were obtained for all subjects in the experimental group and for all experimental tests. The flexion-extension angles at the lower limbs joints have a pronounced increase with the increase of the walking speed, but also with the increase of the treadmill inclination.
Prosthetic alignment is one of the most important factors, both in terms of the correct functioning of neoarticulation and the survival duration of knee arthroplasty. Significant changes in the alignment of prosthetic components affect the distribution of stress in the knee joint. These changes may also affect the distribution of stresses on the contact surface, soft knee joints, and the subjacent bone remodeling under these forces. The malposition of the components and, in particular, the tibial component in the varus, which in practice is the most common situation alongside the malrotation of the femoral component, leads to the excessive intimal tension of the internal tibial plate by the summing of the additional stresses at this level with its physiological loading from during the unipodal support phase during the walk. Although valuable, all of these studies have no capacity to assess these changes in the kinetics of in vivo knee arthroplasty. Two methods are used for this: telemetry and mathematical models. Traditionally, telemetry has been used to determine the forces acting on the hip, and more recently, on the knee. It values very precisely the value of the axial rotation forces as well as the moments of bending; however, this method is little used, because the necessary equipment is very expensive. Taking this into account, the most used method is the finite element method. The objective of this study was to investigate the effect of malpositioning in the valgus and varus of the tibial component on tension developed in polyethylene as well as in the subjacent bone. Obviously, other situations have also been analyzed. In this direction a series of original numerical models of the anatomical elements (tibia, fibula, femur) of the knee were constructed to simulate the biomechanical phenomena occurring in the normal and prosthetic joint during physical activities, in order to evaluate the factors that influence the duration operation of total knee prostheses.
The basic concepts of Kuntscher's centromedular osteosynthesis remain largely valid today: centromedular osteosynthesis must be conducted under fluoroscopic control and without fracture outbreak exposure to avoid contamination, the rod must be strong enough to withstand stress caused by muscle contraction, joint movement and body weight load, this to avoid twisting and tearing the rod, the rod must exhibit sufficient elasticity to compress during insertion into the canal and then re-expand for firmly fix the fracture fragments and prevent their rotation. On the other hand, osteosynthesis with flexible centromedullary rods is mainly used in pediatric surgery where elastic rods in secant arch are used applying the principles of stable elastic osteosynthesis. Starting from the research done worldwide, we examined the orthopedic implants used in the long bones as a whole and some inconsistencies were found between the osteosynthesis material and the bone tissue. The necessary materials used in the study are orthopedic implants, different in structure, elasticity, dimensions, which were tested on bone virtual models, according to the CT scan sections. With the help of normal bone virtual models, both bone strength, various orthopedic implants, and the resistance of the osteosynthesis material used were taken into account. On these complete virtual models various simulations were made using FEM. The potential for FEM use in orthopedics and biomechanics has often been overestimated. In many situations, inappropriate use of the method on complicated biological structures can become costly, inefficient or prone to errors. Also, nonlinear soft tissue material has created new difficulties. But these disadvantages and limitations have been diminished successively through new results of biomechanical researches, but also by improving the method by using new types of finite elements. From this results database obtained through various virtual experiments, account will be taken of the most common accidents and incidents occurring in the implanted bone, and solutions will be sought to improve post-implant bone quality.
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