Finite element study regarding the influence of the cement mantle thickness on the stress distribution in a cemented hip joint

The disrupted function of the hip joint can be restored by means of total hip arthroplasty (i.e. reconstructive surgery of the joint) THA. This is a widely used medical strategy with high succes rates, world wide [1,2]. Among the failure scenarios of THA, aseptic loosening represents the main reason for revision of cemented hip implants [3]. Studies have shown that the two most frequent ways for aseptic loosening to occur are stem-cement debonding and cement cracking [4]. They are followed by subsidence and micromotion of the stem inside the cement mantle [5], with corresponding wear of particles causing osteolysis (i.e. degenaration of the bone tissue) [6] and accelerating bone resorption [7]. Hip replacement implants must be firmly attached to bone in order to support the given forces [8]. The THA implant is placed in the femoral bone either with an acrylic cement that gradually fails as regeneration of connecting bone tissue is proceeding, or without cement using an implant designed to obtain the necessary attachment. Cemented implants are the most common used in THA surgery. Despite good design, THA surgery still heavily relies on the experts experience and ability to avoid any irreversible damage on bone tissue. In the optimising process to find the ideal hip prosthesis geometry and surgical procedures, pre-clinical tests must be carried out to guarantee mechanical endurance to physiological loads and good healing. This is never an easy and simple task, but can be solved using an alternative aproach based on mathematical models. Accordingly the bone-cement-implant interface can be studied with computer simulations. The finite element method (FEM) is an advanced simulation technique that has been used in orthopedic biomechanics since 1972. It is an important tool used in the design and analysis of total joint replacements and other orthopedic devices. FEM modeling and analysis present a non-destructive design approach. It allows many what-if scenarios to be studied in computer environment before the prosthesis is actually inserted. This simulation streamlines the design and prevents any permanent damage caused by mis-implementation. The succes and performance of cemented THA implants remain a question of prosthesis atthachment to bone. Initial loss of fixation is due to failure in the bone-cement-implant Finite element study regarding the influence of the cement mantle thickness on the stress distribution in a cemented hip joint