Finite element analysis of the effect of cementing concepts on implant stability and cement fatigue failure

Background and purpose Two contradictory cementing techniques (using an undersized stem versus a canal-filling stem) can both lead to excellent survival rates, a phenomenon known as the “French paradox”. Furthermore, previous studies have indicated that the type of bone supporting the cement mantle may affect implant survival. To further evaluate the mechanical consequences of variations in cementing technique, we studied the effect of implant size and type of bone supporting the cement mantle on the mechanical performance of cemented total hip arthroplasty, using finite element analysis

Basic Science Considerations in Primary Total Hip Replacement Arthroplasty

Total Hip Replacement is one of the most common operations performed in the developed world today. An increasingly ageing population means that the numbers of people undergoing this operation is set to rise. There are a numerous number of prosthesis on the market and it is often difficult to choose between them. It is therefore necessary to have a good understanding of the basic scientific principles in Total Hip Replacement and the evidence base underpinning them. This paper reviews the relevant anatomical and biomechanical principles in THA. It goes on to elaborate on the structural properties of materials used in modern implants and looks at the evidence base for different types of fixation including cemented and uncemented components. Modern bearing surfaces are discussed in addition to the scientific basis of various surface engineering modifications in THA prostheses. The basic science considerations in component alignment and abductor tension are also discussed. A brief discussion on modular and custom designs of THR is also included. This article reviews basic science concepts and the rationale underpinning the use of the femoral and acetabular component in total hip replacement

Favourable mid-term results of the VerSys CT polished cemented femoral stem for total hip arthroplasty

We evaluated the mid-term clinical and radiographical performance of a cohort of patients who underwent primary total hip replacement with a modern, forged cobalt–chrome, polished cemented femoral stem with proximal and distal centralisation. Sixty-seven patients with 73 hybrid total hip replacements were followed up clinically and radiographically for an average of 6.1 years (4–8.5). No patient was lost. No hips required revision, and all stems are radiographically well-fixed. Four hips developed localised osteolysis: one at the site of a proximal periprosthetic fracture, another at the level of a lateral femoral window of a previous core decompression, the third at the mid third of the femoral component, and the fourth on the greater trochanter, associated with accelerated polyethylene wear. This modern polished stem yielded excellent, predictable clinical and radiographic results at an intermediate follow-up

Long-term results of the standard Wagner cup

Cementless acetabular components gained popularity because of the increased rate of loosening associated with cemented cups after intermediate and long-term follow-up. There are few long-term follow-up studies of cementless acetabular components. This study aims to evaluate the clinical and radiological long-term results of the press-fit standard Wagner Cup. Between January 1, 1994 and June 30, 1994, 118 implantations of a standard Wagner Cup were performed, and 102 implants were clinically and radiographically followed-up after a mean of 12.0 years. The Merle d’Aubigné score improved from a preoperative mean of 9.5 to 17.2 at latest follow-up. Early postoperative complications included two deep haematomata requiring needle aspiration, two deep vein thromboses, one pulmonary embolism, two temporary lesions of the sciatic nerve, one single event of THR dislocation and one recurrent dislocation. Two isolated cup revisions and five more complete total hip replacements were performed for aseptic loosening. The overall survival rate at 12 years was 93.1% (95/102). The standard Wagner cup yields very good long-term results