Manufacturing & biomechanical analysis of a human shoulder joint: A methodology review

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1 American Journal of Mechanical Engineering and Automation 2014; 1(5): Published online September 30, 2014 ( Manufacturing & biomechanical analysis of a human shoulder joint: A methodology review Rahul Manohar Sherekar 1,*, Anand Pawar 2, Paresh Bheda 3 1 Department of Mechanical Engineering, Jawaharlal Darda Institute of Engineering and Technology, Yavatmal, Pin , (M. S), India 2 Department of Mechanical Engineering, Government Polytechnic, Amravati (M. S). India 3 Director, Protosys Technologies Pvt.Ltd.Mumbai, , India address rahulsherekar@yahoo.com (R. M. Sherekar) To cite this article Rahul Manohar Sherekar, Anand Pawar, Paresh Bheda. Manufacturing & Biomechanical Analysis of a Human Shoulder Joint: A Methodology Review. American Journal of Mechanical Engineering and Automation. Vol. 1, No. 5, 2014, pp Abstract The paper involves building of humerus joint in relatively short time to help create and test various design features, ideas, concepts, functionality and in certain instances customization and performance. Rapid Prototyping technologies perform fabrication of implants in a highly controlled atmosphere which results in especially high purity. The layer-by-layer principle allows the fabrication of customized implants that fully fit patient s data. The biomechanics is the theory of how tissues, cells, muscles, bones, organs and the motion of them and how their form and function are synchronized by basic mechanical properties. A finite element model of bones with accurate geometry and material properties retrieved from CT/MRI scan data are being widely used to make realistic investigations on the mechanical behaviour of bone structures. In the human body structure the shoulder complex is the functional unit that results in movement of the arm with respect to the trunk. This unit consists of the clavicle, scapula and humerus; the articulations linking them; and the muscles that move them. These structures are so functionally interrelated to one another that studying their individual functions is almost impossible. The present paper focuses on the anatomy, 3D scanning and modelling of humerus, scapula and clavicle. Finite element modelling of the ligaments and the muscles are carried out using the hexa-penta mesh elements in Hyper-Mesh. This meshed model is then analysed for Von Mises stresses for flexion and extension motions at different points using the advance simulation tool for non-linear analysis (LS Dyna). The results of this analysis are helpful for orthopedic surgeons for pre & post operative planning. Keywords 3D scanning, CAD modeling, Rapid prototyping, Biomechanics, FEA (Finite Element Analysis) 1. Introduction Modern advanced medical imaging techniques, such as whole body scanners, can accurately map out the dimensions of bones or body organs of a living person. These measurements can be used to make computer models of the body parts from which full-scale plastic copies can be used for planning surgery or shaping replacement joints. Rapid Prototyping techniques can also be used for operation planning surgery rehearsal, training and prosthesis design. Along with this biomechanics includes application of mechanical principles to the biological objects. It is not so simple to apply mechanical laws to biological objects. Artificial objects are simples in shape and they can be easily modelled whereas biological objects posses complex shape which are difficult to prepare CAD model. Advanced processing power of computers has made it easy to simulate the biological objects possessing complexity in shape, nonlinearity and anisotropy in properties. The scientific research in the field of structural optimization has increased very substantially during the last decades, and considerable progress has been made. This development is due to the progress in reliable general analysis tools like the finite element method, methods of design sensitivity analysis. Interfacing directly medical data

2 43 Rahul Manohar Sherekar et.al.: Manufacturing & Biomechanical Analysis of a Human Shoulder Joint: A Methodology Review to a FEA and CAD environment can improve the biomechanical analysis of joints and the design process of orthopedic implants providing very useful geometric information of various joints of body. The model used representing an ideal human bone or of specific age, weight and height which was reconstructed from CT (Computed tomography) or MRI (Magnetic resonance imaging) scan image. Then the model is imported to CAD software. After forming a CAD model of particular bone it is proceed for FEA (Finite Element Analysis) by using various FEA software ( e.g. Hyper mesh ). At last the obtained results of the analysis are applicable for constructing a prototype of a selected bone or for other various medical applications. This present paper try to convey the methodology to analyze human bones and various joints of a body. The shoulder joint is one of the complex joint of human body, it is our shoulder which made us possible to move our hand in any direction with respect to the trunk. To manage this, the shoulder must have the right balance of strength, flexibility and stability. For this purpose the analysis of shoulder joint is important. 2. Aim and Objective The main objective of present paper is to fabricate & analyze the study of methodology of various bones and joints of body. Shoulder has largest movements than any other parts in the body. Human cant able to put a single movement of a hand without a shoulder joint. That s why it is very important to create and analyze the CAD model of a shoulder joint in the case of fracture and implants. The analysis of stress distribution in the various bones and joints of shoulder joint will be applicable to orthopedic surgeons for pre-analysis of the surgery. The output of this would be useful in applications like surgery, manufacture of personalized artificial limbs etc. rapid prototyping is the next phase that would be adopted in the manufacture of the desired joint. By the application of these CAD Model techniques the worn out part such as shoulder joints in the human body can be replaced by some artificial implants. joint of the improved model of shoulder joint. This was due to the fact that it was difficult to coordinate the simultaneous motion of the shoulder components in a consistent way. On the basis of former biomechanical investigations, they proposed an extended shoulder model including scapulothoracis constraint and joint sinus cones [4]. Douglas D. Robertson and his colleagues studied sixty clavicles and built 3-D computer models from canal and contours extracted from computerized homographic data and multiple measured anatomical parameters, including humeral canal axis, humeral head center, and hinge point offset and humeral head center [5]. Daniel Kluess, Jan Wieding and Rober souffarnt use finite element method (FAE) for implant in orthopedic surgery of total hip replacement (THR). Firstly they presented a convenient modus operandi of generating FE-models of the implant bones compounds and developed computed tomograms of biological structures for computational finite element- analysis an corresponding CAD-models of the implant [6], [7]. Prof. D. S. Ingole et.al highlighted the efforts made to improve the application potential of the fused deposition modelling (FDM) process by producing the rapid prototyping parts at minimum cost. Also focused on Build orientation analysis for prismatic, curved boundary, and complex shaped machine, biomedical parts is carried out. The mathematical model is formulated to estimate the total cost of part preparation in fused deposition modelling[9]. 4. Anatomy of a Shoulder Joint The shoulder has the greatest range of motions than any joint in the body. It is our shoulders that allow us to put our hands where they need to be. To manage this, the shoulder must have the right balance of strength, flexibility and stability. Loss of this balance can lead to pain and injury. The human shoulder is made up of three bones: the clavicle, the scapula and the humerus as follows. 3. Literature Review Medappil describes the techniques to utilize the advanced Computer Aided Design (CAD) / Finite Element Analysis (FEA) to detect and understand the stress points in the various joints of the human body such as knee, hip and the shoulder joints.[1] Chawla A, Indian Institute Of Technology; New Delhi refers the finite element analysis (FEA) of human bones from CT/MRI scan.[2] Carol Oatis, studied the mechanics and path mechanics of movement of human shoulder joint. [3] Walter Maurel and Daniel Thalmann investigated the problems regarding the realistic animations of the shoulder Fig 2. Anatomy of shoulder Clavicle: The clavicle is a long bone. It supports the shoulder so that the arm can swing clearly away from the trunk. The clavicle transmits the weight of the limb to the sternum. The bone has a cylindrical part called the shaft and two ends, lateral and medial. Humerus: The humerus is the bone of the arm. It is the longest bone of the upper limb. It has an upper end, a lower

3 American Journal of Mechanical Engineering and Automation 2014; 1(5): end and a shaft. Scapula: The scapula is a thin bone placed on the posterolateral aspect of the thoracic cage. The scapula has two surfaces, three borders, three angles and three processes. Joints of shoulder joint: The four major joints of the shoulder complex are Sternoclavicular joint, Acromioclavicular joint, Scapulothoracic joint and Glenohumeral joint 5. Methodology The fabrication & analysis of human bone can be carried out by using following steps Scanning Process Geometrically accurate and anatomically correct 3D geometric model of human bone and implants are essential for successful preoperative planning in orthopedics surgery. There are several medical scanning techniques such as CT (Computed Tomography), MRI ( Magnetic Resonance I) available in present era. In the data acquisition step of 3D scanning method, the bone that is to be scanned is replaced on the bed of the digitizer. The ATOS sensor head mounted on a tripod can easily be positioned relative to the bone. The laser probe projects a line of laser light onto the surface while 2 sensor cameras continuously record the changing distance and shape of the as it sweeps along the object. The result of the measurement is directly displayed. By rotating the object further scan be acquired without changing the relative position of object and reference point. In the next step all scans are imported into Geomagic Studio and merged into one single data set. The automatic meshing procedure creates about 8 million triangles in 10 to 15 minutes of processing time. The cleaning procedure of Geomagic Studio re-adjusts neighbouring triangles which shows large orientation differences. Using 3D scanning and digital software it was possible to scan and construct the object with sharpened edges shown in fig3,[8]. Fig D scanning & reconstruction of neighbouring triangles the object with sharpened edges Cad Modelling Modelling of a human bones using CAD software means generating digital 3D model of bones geometry from 3D scanned model. In this particular case CATIA V5R20 CAD software and its module were shown in fig4. Fig. 4. -Modelling of Bones in Catia V5. 6. Fused Deposition Modelling (FDM) Fused Deposition Modelling (FDM) is a rapid prototyping (RP) process that integrates computer aided design, polymer science, computer numerical control, and extrusion technologies to produce three dimensional solid objects directly from a CAD model using a layer by layer deposition of molten thermoplastics extruded through a very small nozzle(fig.5,6). FDM is one of the few commercially available rapid prototyping technologies offering the possibilities of producing solid objects in a range of different materials. The process starts with the creation of a part on a CAD system as a solid model or a closed surface model. The

4 45 Rahul Manohar Sherekar et.al.: Manufacturing & Biomechanical Analysis of a Human Shoulder Joint: A Methodology Review model is converted into an STL file using a specific translator on the CAD system. The STL file is then sent to the FDM slicing and pre-processing software called Quick Slice, where the designer selects proper orientation, creating supports and slicing and other parameters to prepare the part program for sending to FDM machine. Fig. 5. Under construction Humerus bone Fig. 6. Actual manufactured humerus model by FDM As the rapid manufacturing is the additive manufacturing process, model is constructed by layer by layer formation. The above figure is to represent the under construction images of Humerus bone. We used the FDM (fused deposition modeling) technology to manufacture the Humerus bone model 7. Finite Element Analysis (FEA) of Shoulder Joint To analyze human bone structure the non-linear analysis technique is used. It is different approach which is spicily applicable for live or dynamic parts of body. For this purpose Finite Element Analysis ( FEA ) is used. In any FE analysis, the work can be divided into three phases. First is pre-processing i.e. defining the finite element model, then analysis solver implying towards the solution of finite element model and finally post-processing of results using visualization tools Finite Element Modelling Processing the shoulder joint assembled model in Hypermesh required importing the joint in IGES format. Then clean up tool was used for the missing data such as some edges, corners etc. There is a tool available for creating surfaces in design workbench of HyperMesh for the finite element modelling of muscles and ligaments. Here the surfaces are created with integration of Hexa Penta mesh shown in fig 7. For the simulation and analysis of shoulder joint, it is desirable to use a mesh of hexahedral and pentahedral elements due to change in thickness at different points of ligaments and muscles. Fig. 7. Hexa & Penta mesh for the simulation and analysis of muscles and ligaments Material Properties of Different Bones In order to perform the FE analysis of the properties. Based on these properties, we will obtain different stress distribution in the model. The material property values of different bones and muscles are mentioned in the following table. Bones Cortical Bone Cancellous Bone Table 1. Bones Material Properties Young s Modulus Poisson Ratio Yield Stress Density(Kg/m 3 ) Table 2.Museles Material Properties Museles E0 (MPa) Poisson Ratio InfraSpinatus Triceps Subscapularis Meshing Meshing of was carried out after the material properties to each components. In FEA meshing can be done in various ways such tetrahedral, pentahedral, hexa etc. For shoulder joint analysis the bones are meshed in tetrahedral because bone has a irregular structural geometry, and hence triangle is the perfect shape for meshing of bone shown in fig 8, while hexa and penta elements were used for meshing ligaments

5 American Journal of Mechanical Engineering and Automation 2014; 1(5): and muscles. Fig. 8. Tringular mesh for Bones 7.4. Boundary Conditions The boundary conditions are defined in simulation tool LS Dyna. In this particular shoulder joint We have not applied any external load but instead we have considered the self weight of the arm acting on the joint between Humerus and Scapula. The velocity applied on the free end of Humerus is 10 mm/s. 8. Result and Discussions The solved model file is exported to Hyper View for postprocessing. The model can be viewed in various forms and judged by different parameters. In this case, two major parameters are Von Mises stress and displacement of the components. We have studied and worked on the Flexion and Extension movement of the shoulder joint and mentioned the stresses and displacement charts and plots. The following figures and tables describe the various stresses acting on lhe ligaments muscles and bones of the shoulder joint. As we can observe, the maximum stress is obtained at the Teres Minor i.e MPa while the least stress is obtained at the long head of head of triceps which is 0.1 MPa. Table 3. Stresses near the glenohumeral Joint Museles/Ligament Stress (MPa) Subscapularis 0.46 Teres Minor 0.90 Table 4. Stresses on Costal Muscles Museles/Ligament Stress (MPa) Subscapularis 0.10 Teres Major Coracobrachialis 0.39 The stresses obtained after the simulation of shoulder joint vary for various parts on the costal muscles. Maximum stress is obtained at the Teres Major while the least stress is obtained at the Subscapularis muscle. The stress at the Coracobrachialis muscle is 0.39 MPa. Table 5. Stresses on Dorsal Muscles Museles/Ligament Stress (MPa) Supraspinatus 0.22 Infraspinatus 0.39 The maximum stress is obtained at the Teres Minor muscle while the least stress is obtained at the Subscapularis muscle shown in fig 9. The stress at Infraspinatus muscle is 0.39 MPa. Fig. 9. Stress distribution at shoulder joint. The graph 1 represents the variation in the maximum stresses induced with respect to change in time. When the humerus starts displacing itself from the initial position, following the Flexion motion, Von Mises stresses start

6 47 Rahul Manohar Sherekar et.al.: Manufacturing & Biomechanical Analysis of a Human Shoulder Joint: A Methodology Review inducing in the muscles and ligaments as shown in the above graph Maximum stress is induced at 9 micro-seconds when the value is 0.9 MPa. The results observed from this graph validate the previous stress plots. Plot 1. Maximum Stress Vs Time 9. Conclusion The study has revealed that rapid prototyping,has great potential in the manufacturing of customized anatomical implants. Also an attempt has been made to explain the methodology and the process of human bone model analysis. The analysis of the shoulder joint was performed by using high end analysis softwares such as LS Dyana and HyperMesh. The scope of the project can further be enhanced by assembling the further bones of human arm, radius and ulna. More detailed analysis of other shoulder movements such as Abduction, External Rotation, Internal rotation can be carried out. Same approach can be used to model, simulate and analyze various human bones and joints. References [1] Kukv Medappil CAD/CAE in Biomedical Field IEEE Transactions On Image Processing,pp [2] Chawla A1, Mukherjee S 2and Sharma G3 Indian Institute Of Technology; New Delhi, Finite Element Meshing Of Human Bones From MRI/CT Raw Data. [3] Carol Oatis, Kinesiology: The mechanics and pathomechanics of human movement, Lippincott Williams & Wilkins 2009, [4] W. Maurel, D. Thalmann, Human shoulder modelling including scapulo-thoracic constraint joint sinus cones, Computers & Graphics, vol. 24, 2000, [5] Douglas D. Robertson et al, Three-dimensional analysis of the proximal part of the humerus relevance to arthroplasty, The Journal of Bone and Joint Surgery, 82-A (11), [6] Rho, J. Y., M. C. Hobatho, et al. Relations of mechanical properties to density and CT numbers in human bone, Med Eng Phys 17(5), 1995, [7] Snyder, S. M. and E. Schneider, Estimation of mechanical properties of cortical bone by computed tomography, J Orthop Res 9(3), 1991, [8] Brian Curless, From range scans to 3D models, Computer Graphics, 33 (4), 2000, [9] Prof.D.S. Ingole, Build orientation analysis for minimum cost determination in FDM, Proc. IMechE Vol. 225 Part B: J. Engineering Manufacturing.