Abstract—Design of hip prosthesis is believed to be an important factor to minimize the aseptic loosening problems and to encourage long term stability. The numerous changes in the cemented femoral stem design have been intended to improve the long term performance of the implants, although have had other negative consequences. In this study, a finite element model of the implanted proximal femur to examine stresses behaviors in cemented hip arthroplasty with different tapered design of prosthesis. The calculated stress distribution is discussed with respect to stress shielding and bone remodeling issues in THR femur case. The taper of the prosthesis were design to be 3° at anterior/posterior, 3° at medial/lateral and 10° from wide lateral to narrow medial. Two different load cases representing walking (toe-off phase) and stair-climbing activities are investigated. Proper stress and strain distribution along the femur will enhance bone growth and keep the femur to function as normal as intact femur. Index Terms— aseptic loosening, hip arthroplasty, stem tapers, stress shielding. I. INTRODUCTION Cemented hip arthroplasty become popular since it was introduced by John Charnley in 1972. The long-term clinical follow-up studies have demonstrated outstanding performance of Charnley’s prosthesis. However, the challenge of aseptic loosening of prosthesis remains, frequently reported in young and active patients. It is due to heavy mechanical demands on their reconstructed joints. The design of hip prosthesis is believed to be an important factor to minimize the aseptic loosening problems and to encourage long term stability. Aseptic loosening may occurred due to biomechanical factors such as osteolysis induced by wear debris of bone cement, cement mantle fracture, and poor bone remodeling triggered by stress shielding [1-2]. Nowadays, the Charnley prosthesis is still the most commonly implant used and is regarded as the reference designs. A large number of long term clinical follow up Manuscript received December 21, 2009. This work was financially supported by the Universiti Teknologi MARA Malaysia. A.H. Abdullah is with the Faculty of Mechanical Engineering, Universiti Teknologi MARA, 40450 Shah Alam, MALAYSIA (phone: 603-5543-6468; fax: 603-5543-5160; e-mail: halim.fkm.uitm@gmail.com). M.N. Mohd Asri is with the Faculty of Mechanical Engineering, Universiti Teknologi MARA, 40450 Shah Alam, MALAYSIA (e-mail: mohdasri.mohdnor@gmail.com). M.S. Alias is with the Faculty of Mechanical Engineering, Universiti Teknologi MARA, 40450 Shah Alam, MALAYSIA (e-mail: aliasms1@gmail.com). T. Giha is with the Mechanical Engineering Department, Politeknik Sultan Salahuddin Abdul Aziz Shah, Ministry of Higher Education, 40150 Shah Alam, MALAYSIA (e-mail: giha_83@yahoo.com). studies have shown that the Charnley prosthesis, especially its femoral component with polished surface finish, has greatly performed. Its also became a main references of evolutionary in new designs of femoral stem. For example, more than a hundred different type of prosthesis were used in Sweden from 1967 to 1990 [3]. The numerous changes in the cemented femoral stem design have been intended to improve the long term performance of the implants, although have had other negative consequences. In many cases, in attempting to solve on particular problem, another problem has inadvertently been introduced [4]. Revolutionary of prosthesis design continues with improvement of Charnley prosthesis with taper in the anterior/posterior plane and it was known as Charnley’s Flatback. Later in early 1970s, Robin Ling designed a double tapered prosthesis which identically had a second taper in medial/lateral plane [5]. The prosthesis was highly polished, collarless, and stainless steel was also known as Exeter prosthesis. It is reported that it was successfully reduced aseptic loosening problems after 21 years follow-up period [4]. In conjunction to the successor of prosthesis design, Wroblewski has design and implanted a collarless, polished and triple tapered prosthesis since early 1990s. Results at 5 years suggested that the theoretical benefits of the stem are being realized clinically [5]. The modifications were keep established by improving different designs and parameters such as taper stems, stem sizes, materials used and surface roughness. Every modified parameter is believed to improve overall performance but it may also contribute to others failure. The aim of this study was to use a finite element model of the implanted proximal femur to examine stresses behaviors in cemented hip arthroplasty with different tapered design of prosthesis. The calculated stress distribution is discussed with respect to stress shielding and bone remodeling issues in THR femur cases. II. FINITE ELEMENT MODEL Finite element (FE) model of the intact femur was reconstructed from a normal healthy bone dataset [6]. The model was reconstructed and rigorously examined for the biomechanics responses to physiological loads. Since the top-half region of the femur is of particular interest, only this part was considered in the analysis. The femur model was discretized into 44,714 elements using ten-node quadratic tetrahedron elements. Similar femur geometry was modified to represents THR femur cases with Charnley’s prosthesis. Effects of different types of taper prosthesis on the resulting Finite Element Analysis of Cemented Hip Arthroplasty: Influence of Stem Tapers Abdul H. Abdullah, Mohd N. Mohd Asri, Mohd S. Alias and Tardan Giha, Member, IAENG Proceedings of the International MultiConference of Engineers and Computer Scientists 2010 Vol III, IMECS 2010, March 17 - 19, 2010, Hong Kong ISBN: 978-988-18210-5-8 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) IMECS 2010