INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET)

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1 INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN (Print) ISSN (Online) Volume 4, Issue 4, July - August (2013), pp IAEME: Journal Impact Factor (2013): (Calculated by GISI) IJMET I A E M E BIOMECHANICAL STUDY, 3D MODELING AND KINEMATIC ANALYSIS OF SHOULDER JOINT Pranav Birajdar 1, Shruti Bammani 2, Pravin Shinde 3, Rahul Bhandari 4, Jaya Bedare 5 1, 2,3,4,5 Department of Mechanical Engineering, N.K. Orchid College of Engineering and Technology, Solapur, Maharashtra, India ABSTRACT 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 HyperMesh. This meshed model is then analysed for Von Mises stresses for flexion and extension motions at different points using LS Dyna. Keywords: 3D scanning, Biomechanics, CAD modelling, Extension, Flexion 1. INTRODUCTION 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. Maintaining this balance through exercises aimed at stretching and strengthening can help to avoid shoulder problems [1]. 2. LITERATURE REVIEW Walter Maurel and Daniel Thalmann investigated the problems regarding the realistic animations of the shoulder 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 97

2 way. On the basis of former biomechanical investigations, they proposed an extended shoulder model including scapulothoracic constraint and joint sinus cones [2]. Douglas D. Robertson and his colleagues studied sixty cadaveric humeri and built 3-D computer models from canal and periosteal contours extracted from computerized tomographic data and multiple measured anatomical parameters (Siemens Somatom Plus S scanner), including humeral canal axis, humeral head center, and hinge point offset; greater tuberosity and humeral head center [3]. Daniel Kluess, Jan Wieding and Robert Souffrant used finite-element-method for implant in orthopaedic surgery of total hip replacement (THR). Firstly they presented a convenient modus operandi of generating FE-models of the implant-bone-compound and developed computed tomograms of biological structuress for computational finite element-analysis and corresponding CAD-models of the implant [4], [5]. 3. ANATOMY OF SHOULDER JOINT The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The major joint of the shoulder is the glenohumeral joint, which "shoulder joint" generally refers to. In human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula, the head sitting in the glenoid fossa. The shoulder is the group of structures in the region of the joint 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. Figure I: Anatomy of Shoulder Joint 3.2. 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 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. 98

3 3.4. Joints of shoulder joint The four major joints of the shoulder complex are Sternoclavicular joint, Acromioclavicular joint, Scapulothoracic joint and Glenohumeral joint [6]. 4. 3D SCANNING AND MODELING OF BONES Geometrically accurate and anatomically correct 3D geometric models of human bones and implants are essential for successful preoperative planning in orthopaedic surgery. Such models are often used in various software systems for the preparation surgical interventions. Therefore, it is very important to create geometry of the bone rapidly and accurately [7] Scanning Process In the data acquisition step of 3D scanning method, the bone that is to be scanned is placed 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 bone as it sweeps along the object. The result of the measurement is directly displayed. By rotating the object, further scans can be acquired without changing the relative position of object and reference points. 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 show large orientation differences. Using 3D scanning and digital software it was possible to scan and construct the object with sharpened edges [8]. Figure II: Scanned Models of Humerus, Clavicle and Scapula 4.2. CAD Modelling Reverse 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 modules were used. Figure III: 3D Models of Humerus, Clavicle and Scapula 99

4 5. FINITE ELEMENT ANALYSIS (FEA) OF SHOULDER JOINT 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 modeling of muscles and ligaments. Here the surfaces are created with integration of Hexa- Penta mesh. 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. Figure IV: HyperMesh View of Shoulder Joint 5.2. Material Properties In order to perform the FE analysis of the model, we have to apply certain material 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 Table I: Material Properties of Bones Young s Modulus Poisson Ratio Yield Stress (MPa) (MPa) Cortical Bone Cancellous Bone Density (Kg/m 3 ) Table II: Material Properties of Muscles Muscles Infraspinatus Eo (MPa) 1.2 Poisson Ratio 0.45 Subscapularis Triceps

5 5.3. Meshing Meshing of the model was carried out after the material properties to each component. Tetra elements were used for meshing the bones while hexa and penta elements were used for meshing ligaments and muscles. The meshed models are depicted in Fig. V. 6. RESULTS Fig. V: Meshed Model of Humerus, Clavicle and Scapula The solved model file is exported to HyperView for post-processing. The model can be viewed in various forms and judgedd by different parameters. In this case, two major parameters are Von Mises stress and displacement of the components. The boundary conditions are defined in LS Dyna. The farther end of the Clavicle is fixed so that the other end of the Clavicle which joins the Humerus and the Scapula is in relative motion. 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. 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 the ligaments, muscles and bones of the shoulder joint. Table III: Stresses near the Glenohumeral Joint Ligament / Muscle Stress Teres Minor 0.90 MPa Subscapularis 0.46 MPa 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 triceps which is 0.01 MPa. Table IV: Stresses on Costal Muscles Ligament / Muscle Stress Teres Major Coracobrachialis Subscapularis MPa 0.39 MPa 0.10 MPa 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. 101

6 Table V: Stresses on Dorsal Muscles Name of Ligament Stress Infraspinatus 0.39 MPa Supraspinatus 0.22 MPa The maximum stress is obtained at the Teres Minor muscle while the least stress is obtained at the Subscapularis muscle. The stress at the Infraspinatus muscle is 0.39 MPa. Fig. VI: Von Misses Stresses on Glenohumeral Joint and Costal Muscles Fig. VII: Von Misses Stresses on the Dorsal Muscles The graph 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 inducing in the muscles and ligaments as shown in the above graph. Maximum stress is induced at 8 micro-seconds when the value is 0.9 MPa. The results observed from this graph validate the previous stress plots. 102

7 Fig. VII: Graph of Maxima of Effective Stresses with Respect to Time 7. CONCLUSION An attempt has been made to achieve accurate results by using state-of-the-art 3D scanner for achieving accurate dimensions and using high end analysis softwares for the kinematics analysis. The analysis of the shoulder joint was performed by using high end analysis softwares such as LS Dyna 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, Adduction, External Rotation, Internal rotation can be carried out. Same approach can be used to model, simulate and analyze various human bones and joints. 8. ACKNOWLEDGEMENTS The authors want to thank Mr. Shriniwas Metan and Dr. Vyankatesh Metan for their invaluable guidance in biomechanics and anatomy of shoulder joint. We would also express our deep gratitude to Mr. Jitendra Jagtap, the founder of Optimizt Technologies, Pune for their guidance on finite element modeling and analysiss of shoulder joint. 9. REFERENCES [1] Carol Oatis, Kinesiology: The mechanics and pathomechanics of human movement, Lippincott Williams & Wilkins, 2009, [2] W. Maurel, D. Thalmann, Human shoulder modelling including scapulo-thoracic constraint and joint sinus cones, Computers & Graphics, vol. 24, 2000, [3] 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), [4] 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,

8 [5] Snyder, S. M. and E. Schneider, Estimation of mechanical properties of cortical bone by computed tomography, J Orthop Res 9(3), 1991, [6] B D Chaurasiya, Human anatomy: Upper limb & thorax, CBS Publishers & Distributors, New Delhi, 2004, [7] M. Viceconti, C. Zannoni, L. Pierotti, TRI2SOLID: an application of reverse engineering methods to the creation of CAD models of bone segments, Computer Methods and Programs in Biomedicine, Vol.56, 1998, [8] Brian Curless, From range scans to 3D models, Computer Graphics, 33 (4), 2000, [9] Mayuri Y. Thorat and Vinayak K. Bairagi, Hybrid Method to Compress Slices of 3D Medical Images, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 2, 2013, pp , ISSN Print: , ISSN Online: