Effect of the crack position in the cement mantle on the fracture behavior of the total hip prosthesis A. Flitti a , D. Ouinas a , B. Bachir Bouiadjra b,c, * , N. Benderdouche d a LMNEPM, Department of Mechanical Engineering, University Ibn Badis of Mostaganem, 27000, Algeria b LMPM, Department of Mechanical Engineering, University of Sidi Bel Abbes, 22000, Algeria c Department of Mechanical Engineering, College of Engineering, King Saud University, Riyadh, Saudi Arabia d SEA2M, Department of Process Engineering, University Ibn Badis of Mostaganem, 27000, Algeria article info Article history: Received 13 March 2010 Received in revised form 22 May 2010 Accepted 27 May 2010 Available online 25 June 2010 Keywords: Total hip prosthesis (TPH) Stress intensity factor (SIF) Crack Cement Finite element analysis abstract The mechanical resistance of the total hip prosthesis (THP) and particularly the adhesion quality between the implant and the bone depend primarily on the nature of the cement used and its mechanical and geo- metrical characteristics. The fracture behavior of the cement is decisive in the failure of the cemented THP. In this work, an analysis of the different criteria of crack propagation in the cement using the finite element method was carried out on various regions of the cement (proximal, medial and distal) with a distributed load on the femoral head of the THP of a 90 kg average body weight. Three orientations of the initial crack were considered: horizontal, vertical and inclined. The two first move in the proximal part towards the distal part, and the third moves in the distal zone. The results show that a crack started in the distal zone of the cement propagates in mixed mode, whilst the one initiated in the proximal zone in mode I. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction In spite of the improvement in material design and surgical techniques, many problems related to surgical practices remain unsolved. The strain and wear of the acetabulum components often occur, leading to gradual loosening. Bone cements are widely used in orthopedic surgery mainly for fixation of prostheses. Although the best cemented prostheses show very good clinical results [1], the cement is considered a weak link bay [2]. Upon polymerization must lead to shrinkage of cement and leads to development of residual stress [3]. The residual stresses can directly affect the fu- ture mechanical performance of the bulk cement, stem–cement, and bone–cement interface leading to final failure of the fixation [4]. The mechanical resistance of the total hip prosthesis and par- ticularly the adhesion quality between the implant and the bone depend primarily on the nature of cement used and its mechanical and geometrical characteristics [5]. Cement must withstand the subjected mechanical stresses which may lead to the creation and propagation of cracks, and to the collapse of the whole THP structure [5]. Therefore, the fracture behavior of the cement is an important factor to determine cement–bone adhesion strength and consequently, THP service life. The deterioration of interface between the cement, femur, and metal stem is recognized as the most cause for loosening failure of artificial hip joints [6,7]. The failure behavior of the fixation interface is ascribed to the initiation and propagation of cracks from defects along the bonded surfaces between cement and bone [7–9]. Three kinds of cracks can be identified in orthopaedic ce- ments, cracks initiated at porosities; crack initiated during the polymerisation and cracks initiated in the cement by internal ten- sion [10]. This study aims at analyzing the propagation criteria of cracks to predict the failure behavior of cemented hip prostheses under the monotonic loading conditions using the finite element method code ABAQUS 6.7.1. This analysis was carried out on various zones of cement along the bone, namely the proximal, the medial and the distal positions (see Fig. 1). We studied the mechanical fracture behavior of a total hip prosthesis under the effect of an average body weight of 90 kg. For this purpose, we computed the stress intensity factor (SIF) in various areas of the orthopedic mantle ce- ment. This evaluation takes into account two parameters, namely the displacement of the horizontal crack and vertical crack in ce- ment and the effect of crack inclination at an angle a with respect to the horizontal plane. 2. Geometrical and finite element models The geometrical model in the present study is a 2D model of the prosthesis, orthopedic cement and femoral bone (Fig. 2). The 0927-0256/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.commatsci.2010.05.056 * Corresponding author at: LMPM, Department of Mechanical Engineering, University of Sidi Bel Abbes, 22000, Algeria. E-mail address: bachirbou@yahoo.fr (B.B. Bouiadjra). Computational Materials Science 49 (2010) 598–602 Contents lists available at ScienceDirect Computational Materials Science journal homepage: www.elsevier.com/locate/commatsci