The Study Of The Stability After Total Hip Replacement

The main objective of the THA is pain relief and constructing a steady joint with satisfactory activity. The causes leading to surgical failure of instability lie in aseptic loosening around the femur and the acetabular cup and dislocation around the head-cup connection. There is a close relevance between aseptic loosening around the femur and the acetabular cup and the stress change after THA whether in the near future or in the long run. It turns out to be the postoperative growth and reconstruction around the femur clinically and radiologically whether it is cemented or not. There may be severe loss of the bone matrix, especially proximal, which will result in the joint instability. The loosening will be more commonly seen around the cup which relates to the stress of the polyethelene insert. The hip dislocation after THA is a severe and common complication, it is the mostly behave to the joint instability Consequently, we will discuss the joint stability through four aspects as follows:Section 1: Finite element analyses of changes infemoral stresses after total hip arthroplasty1: Summary of Background DataThe stress distribution in the femur wether near period or the long-term joint stability all has something to do with Total Hip Arthroplasty(THA), wether is a bone cement type or not bone cement type. It is clinical and radialization to all discovery the bone growth and rebuild in the femur side especially near carry after THA can appear the serious bone substance to lose, causing a femur side unsteady. The natural stress distribution in the femur is significantly altered after total hip arthroplasty. Whenan implant is introduced, it will carry a portion of the load, causing a reduction of stress in some regions of the remaining bone. This phenomenon is commonly known as stress shielding. In response to the changed mechanical environment the shielded bone will remodel according to Wolff's law, resulting in a loss of bone mass through the biological process called resorption. Resorption can , in turn, cause or contribute to loosening of the prosthesis. The problem is particularly common among younger. So reducing stress shielding is an important standard of prosthesis design and clinicians and patients will benefit if accurate methods of predicting and monitoring bone strength in-vivo are available. Except for in vitro experiment research based on cadaver, non-invasive tools suitable for proximal femoral strength prediction include quantitative computed tomography (QCT) and dual energy X-ray absorptiometry (DXA). They provide regional bone density evaluations for specific portions of the proximal femur, and can estimate bone size, which has been related to bone resorption after total hip arthroplasty. But previous studies evaluating femoral remodeling after total hip arthroplasty have used QCT and DXA. Limitation of these techniques make it impossible to quantify the magnitude of bone loss in terms of cortical thinning and cortical bone area and bone mineral density changes. In these years, developed with compute technique and mathematic calculus, the three dimension finite element analysis was inducted into biomechanical study. Using excellent quantify calculation ability, finite element analysis method explained further precision than QCT and DXA models. And three-dimensional finite element models become a promising method for predicting bone remodel after total hip arthroplasty. In this study, we explain the changes of femurs stresses after a cemented prosthesis and a cementless prosthesis replacement using finite element analysis method, and make quantity analysis to femoral stresses after THA.2: ObjectiveTo determine the variation in femoral stresses after inserted a cemented and aproximal porous cemnentless femoral prostheses. Using Charnley Elite cemented prosthesis and Summit cementless prosthesis design, we quantify the stress level and stress distribution models after the two different prostheses replacements.3: MethodsConsidering the complex geometry...