Fixation of the Cemented Stem: Clinical Relevance of the Porosity and Thickness of the Cement Mantle

The aim of this review paper is to define the fixation of the cemented stem. Polymethyl methacrylate, otherwise known as “bone cement”, has been used in the fixation of hip implants since the early 1960s. Sir John Charnley, the pioneer of modern hip replacement, incorporated the use of cement in the development of low frictional torque hip arthroplasty. In this paper, the concepts of femoral stem design and fixation, clinical results, and advances in understanding of the optimal use of cement are reviewed. The purpose of this paper is to help understanding and discussions on the thickness and the porosity of the cement mantle in total hip arthroplasty. Cement does not act as an adhesive, as sometimes thought, but relies on an interlocking fit to provide mechanical stability at the cement–bone interface, while at the prosthesis– cement interface it achieves stability by optimizing the fit of the implant in the cement mantle, such as in a tapered femoral stem

Role of high tibial osteotomy in chronic injuries of posterior cruciate ligament and posterolateral corner

High tibial osteotomy (HTO) is a surgical procedure used to change the mechanical weight-bearing axis and alter the loads carried through the knee. Conventional indications for HTO are medial compartment osteoarthritis and varus malalignment of the knee causing pain and dysfunction. Traditionally, knee instability associated with varus thrust has been considered a contraindication. However, today the indications include patients with chronic ligament deficiencies and malalignment, because an HTO procedure can change not only the coronal but also the sagittal plane of the knee. The sagittal plane has generally been ignored in HTO literature, but its modification has a significant impact on biomechanics and joint stability. Indeed, decreased posterior tibial slope causes posterior tibia translation and helps the anterior cruciate ligament (ACL)-deficient knee. Vice versa, increased tibial slope causes anterior tibia translation and helps the posterior cruciate ligament (PCL)-deficient knee. A review of literature shows that soft tissue procedures alone are often unsatisfactory for chronic posterior instability if alignment is not corrected. Since limb alignment is the most important factor to consider in lower limb reconstructive surgery, diagnosis and treatment of limb malalignment should not be ignored in management of chronic ligamentous instabilities. This paper reviews the effects of chronic posterior instability and tibial slope alteration on knee and soft tissues, in addition to planning and surgical technique for chronic posterior and posterolateral instability with HTO

Role of Ligaments in the Knee Joint Kinematic Behavior: Development and Validation of a Finite Element Model

Science Arts & Métiers (SAM)International audienceThe management of knee instability is a complex problem in orthopedic surgery. To comprehensively assess the biomechanical role of the knee joint and to investigate various aspects of knee mechanics, several Finite Element (FE) knee models have been developed. However, (i) the full validation of these models against tibio-femoral and tibio-patellar kinematic data and (ii) the high numerical costs associated with the computation of the biomechanical response of the knee joint are still main issues. Moreover, the contribution on knee mobility of the different ligaments is still unclear. The aim of this study was therefore to develop an FE model with both extensive validation and low computational for the investigation of the role of ligaments in the joint kinematic behavior. To this end, a 3D FE model, consisting of the distal and proximal part of the femur and tibia, respectively, the patella, the quadriceps tendon, the cartilage, and knee ligaments was developed in ANSYS. For the model evaluation, 23 fresh frozen knee joints were tested in flexion/extension using a validated device. The model-predicted response was within or at the limits of the experimental corridors for all translations and rotations of tibia and patella with regard to the femur. A sensitivity analysis was conducted to evaluate the impact of both the stiffness and initial strain of ligaments on the knee kinematic response. Our results showed the high sensitivity of the model to the mechanical parameters of the ligaments