LING AND ANALYSIS PROSTHESIS WITH MODULAR STEM

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 6, June 2017, pp , Article ID: IJMET_08_06_082 Available online at aeme.com/ijm MET/issues.as asp?jtype=ijm MET&VType=8&IType= =6 ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed FINITE ELEME ENT MODEL LING AND ANALYSIS OF HIP JOINT PROSTHESIS WITH MODULAR STEM Taj Assistant Professor, Department of Mechanical MLR Institute of Technology, Hyderabad, Telangana, India E C Prasad Nidumolu Assistant Professor, Department of Mechanical MLR Institute of Technology, Hyderabad, Telangana, India P Geeta Krishna Assistant Professor, Department of Mechanical MLR Institute of Technology, Hyderabad, Telangana, India B Prashanth Kumar Research Scholar, Department of Mechanical Universiti Teknologi Petronas, Perak, Malaysia ABSTRACT The Total Hip joint Replacement (THR) was a surgical procedure where by the diseased cartilage and bone of the hip joint is surgically replaced with an artificial material. The success of implantationn depends on method, material and size of implant used. The present work focused to study the stress distribution in THR by using different modular stems. CAD models of modular stem with differentt cross sections weree modeled to study stress distribution in the area of incision of the implant. Traditionally, large incision of inches which was minimized to 3-4 inches by changing the implant parameters like size, cross section and material. A finite element model of femur bone was developed from CT images using Mimics software and then assembled with modular stems. Finite element analysis for different loading condition was carried out to predict the stress distribution for different implant material. It was observed from finite element analysis that titanium alloy can withstand more load than cobalt chrome alloy whichh was more suited material for implant. The analytical stress value has been validated with theoretical calculated stresss under the assumptions of curved beam theory. Key words: Total Hip Replacemen nt (THR), femur bone, modular stem, CT scan, curved beam theory. 789 editor@iaeme..com

2 Finite Element Modeling and Analysis of Hip Joint Prosthesis with Modular Stem Cite this Article: Taj, E C Prasad Nidumolu, P Geeta Krishna and B Prashanth Kumar. Finite Element Modeling and Analysis of Hip Joint Prosthesis with Modular Stem. International Journal of Mechanical Engineering and Technology, 8(6), 2017, pp INTRODUCTION The hip joint is one of the most important joints in the human body. it bears our body s weight and the force of the hip and leg. the hip joint is a ball-and-socket synovial joint formed between the oscoxa (hip bone) and the femur [1]. A round, cup-shaped structure on the oscoax, known as the acetabuluma, forms the socket for the hip joint. surrounding the hip joint are many tough ligaments that prevent the dislocation of the joint [2]. the strong muscles of the hip region also help to hold the hip joint together and prevent dislocation [3]. Functionally, the hip joint enjoys a very high range of motion. the ball-and-socket structure of the joint allows the femur to circumduct freely through a 360-degree circle. the femur may also rotate around its axis about 90 degrees at the hip joint [4]. only the shoulder joint provides as high of a level of mobility as the hip joint. in addition to being flexible, each hip joint must be capable of supporting half of the body s weight along with any other forces acting upon the body [5]. during running and jumping, for example, the force of the body s movements multiplies the force on the hip joint to many times the force exerted by the body s weight [6]. the hip joint must be able to accommodate these extreme forces repeatedly during intense physical activities [7]. 2. IMPLANT CONSTRUCTION Total hip joint replacement is an orthopedic success story, enabling hundreds of thousands of people to live fuller, more active lives. Using metal alloys, high-grade plastics, and polymeric materials, orthopedic surgeons can replace a painful, dysfunctional joint with a highly functional, long lasting prosthesis. Over the past half-century, there have been many advances in the design, construction, and implantation of artificial hip joints, resulting in a high percentage of successful long-term outcomes. The hip joint is called a ball and-socket joint because the spherical head of the thighbone (femur) moves inside the cup-shaped hollow socket (acetabulum) of the pelvis. To duplicate this action, a total hip replacement implant has three parts: the stem, which fits into the femur; the ball, which replaces the spherical head of the femur; and the cup, which replaces the worn out hip socket. Each part comes in various sizes to accommodate various body sizes and types. In some designs, the stem and ball are one piece; other designs are modular, allowing for additional customization in fit. The stem portions of most hip implants are made of titanium- or cobalt/chromium-based alloys. They come in different shapes and some have porous surfaces to allow for bone in growth. Cobalt/chromium-based alloys or ceramic materials (aluminum oxide or zirconium oxide) are used in making the ball portions, which are polished smooth to allow easy rotation within the prosthetic socket. The acetabular socket can be made of metal, ultra-high molecular-weight polyethylene, or a combination of polyethylene backed by metal. All the materials used in a total hip replacement have four characteristics in common. They are biocompatible. They are resistant to corrosion, degradation, and wear. They have mechanical properties that duplicate the structures they are intended to replace. They meet the highest standards 790 editor@iaeme.com

3 Taj, E C Prasad Nidumolu, P Geeta Krishna and B Prashanth Kumar 2.1. Image based CAD Modeling A 3D finite element (FE) model of femur bone was developed based on a volume reconstruction of tthe he coronal computer tomography (CT) images of the left femur bone of a healthy male (37 years of age, weight 65 kg). CT scan properties were mm mm resolution and 0.75-mm mm slice spacing. The CT dataset was imported into MIMICS version 10 medical image processing ssing software (Materialize, Leuven, Belgium). The images were segmented and the point clouds of femur bone are obtained in fig 1 and 2. The point clouds of femur bone are converted into surface models using Geomagic Studio software are shown in fig. 3. Figure 1 Segmented bone from the soft tissue Figure 2 Segmented model from the CT data (a) (b) Figure 3 (a) Point clouds of the femur bone, (b) Surface model of the femur bone asp 791 editor@iaeme.com

4 Finite Element Modeling and Analysis of Hip Joint Prosthesis with Modular Stem 2.2. Modular Stem Modeling in Unigraphics Modularity, as it applies to the hip replacement implants, refers to the availability of the components in sections or parts, rather than as a single piece the monobloc version. Historically, hip replacements were available as two bits one was meant for insertion into the natural socket and the other, into the femur bone. Fairly good results were obtained by these components, particularly with respect to long term. Figure 4 Modular stem with rectangular & circular cross section Figure 5 Femur Head The modular stem with circular cross section and rectangular cross section shown in fig.4 is modeled in Unigraphics 9 software. Two modular stems with different cross section along with femur head were modeled in Un Unigraphics igraphics 9 as shown in fig However assembly and analysis were carried out only for one modular sstem tem shown in fig 6. 6 Figure 6 Assembly model of femur bone with modular stem asp 792 editor@iaeme.com

5 Taj, E C Prasad Nidumolu, P Geeta Krishna and B Prashanth Kumar 3. FINITE ELEMENT ANALYSIS OF IMPLANTED FEMUR BONE ANALYSIS This study uses stationary condition as the boundary conditionn for the simulation, a buckling load of 1180N was applied on the surface of the femoral head normally and with an angle of 30 as shown in fig 7, while the distal end of the femur is configured as fixed support, and all components in close contact. Cut distance refers to the length between the position and the bottom of the femur which is set as the reference plane. Figure 7 Load acting 30 on femur head surface The assembled femur bone meshed in Hypermesh was then imported to ANSYS 12.0 for performing static analysis. The material properties of femur bone and modular stem are listed in Table 1. Static analysis was performed with buckling load acting normal to surface of femur head and buckling load acting 30 to surface of femur head. Fig 8 shows the stress distribution of the titanium and cobalt alloy implants. Table 1 Material properties of femur bone & modular stem Material Young s modulus (GPa) Poissons ratio Cortical bone Cancellous bone Titanium alloy Cobalt chrome alloy Analysis has been carried out with one implant model with different material properties. A buckling load calculated from buckling load equation of 1180N was applied normal to surface of femur head and with an angle of 30 to surface of femur head. Fig 9 shows the stress distribution at 30 loading angle of titanium alloy and cobalt alloy implants. (a) (b) Figure 8 Stress distribution of (a) Titanium Alloy implant, (b)( Cobalt Alloy implant 793 editor@iaeme..com

6 Finite Element Modeling and Analysis of Hip Joint Prosthesis with Modular Stem (a) (b) Figure 9 Stress distribution at 30 loading angle of (a) Titanium Alloy Implant, (b) Cobalt Alloy Implant 4. CONCLUSIONS The femur bone anatomy and properties have been studied from literature. According to that a natural femur bone has been created from CT scan using Mimics and different modular stems were modeled in Unigraphics software. In the present study one assembly of femur bone with modular stem was done and finite element analysiss was carried out for titanium and cobalt alloy implants. The result indicates that the titanium based implants has more strength compared to cobalt based implant. Stress distributions for both the alloys were studied at different loading condition and it is shown in the table 2. Table 2 Stress distribution of Femur Implant Material Max Stress (MPa) Stresss (Von misses ) load Stress (Von misses) load acted 30 acted normal to surface to surface of femur head (MPa) of femur head (MPa) Titanium alloy implant Cobalt chromium alloy REFERENCES [1] Ji-Yong Bae, Umar Baroque, Kyung-wonn Lee, (2012), Development of hip joint prostheses with modular stems, Elsevier, computer-aidedd design, Vol 3, [2] Sameer Jade, (2012) Finite Element Analysis of a Femur to Deconstruct the Design Paradox of Bone Curvature Master Thesis University of Massachusetts. [3] Amrita Francis, Kumar, (2012), Computational Modeling of Human Femur using CT Data for Finite Element Analysis, Journal of biomechanical, Vol 5, [4] Ming-Chu Shieh1 and Alan, (2011), CAD-model-based Design and Stress Analysis of Resurfacing Hip Joint Prosthesis, journal of biomechanical, Vol 3, [5] Marie-Christine, (2009), Finite element modeling of the vibration behavior of the human femur using CT-based individualized geometrical and material properties Elsevier, computer aided design, Vol 2, editor@iaeme..com

7 Taj, E C Prasad Nidumolu, P Geeta Krishna and B Prashanth Kumar [6] Royo Fideda, Zohar, (2005) Femur mechanical simulation using high-order FE analysis with continuous mechanical properties, Journal of computational bioengineering, Vol 1, [7] Beatrice Chouteau, Marie-Christine, (1998), Finite element modeling of the vibrational behavior of the human femur using CT based individualized geometrical and material properties, Journal of Biomechanics, Vol 2, [8] R R Mandal and U K Dewangan. Finite Element Modeling of Beam with Eight Noded Brick Element Using Matlab. International Journal of Civil Engineering and Technology (IJCIET) 2017, pp , [9] Prof. Shriniwas Metan, Prof. Rahul Bhandari, Azeem Dafedar, Vinay Bangartale, Pankaj Ande. Advances & Development in Biomechatronics- Introduction to Arm Prosthesis. International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 5, Issue 10, October (2014), pp editor@iaeme.com