Application of Advanced Design and Development ...

International Journal of Applied Engineering Research ISSN 0973-4562 Volume 5 Number 9 (2010) pp. 1653–1666 © Research India Publications http://www.ripublication.com/ijaer.htm

Application of Advanced Design and Development Techniques in Orthopaedics D. Chandramohan1, K. Marimuthu2, S. Rajesh3 and M.M. Ravikumar4 1, 3, 4

Research scholar, Department of Mechanical Engineering, Anna University Coimbatore, Coimbatore, India Email: [email protected], [email protected], and 4 [email protected] 2 Asst. Prof. Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, India Email: [email protected]

Abstract This project covers Mechanical Engineering based research directed safety systems which can be successfully implemented in the field of orthopaedics. It includes the development of tool which helps in preventing the fractures usually occur after the fixation of plates over the humerus bone. Fractures mostly occur on femur bones and humerus bones. This project mainly focuses on injury to the shaft of humerus bone. So this project mainly deals with the stress analysis of bone particularly on the humerus bone during the fixation of plate. The deflection of the bone is calculated manually and the value is compared with the ANSYS solution and the aid of rehabilitation of patients having acute pain on upper limp and vertebrae is effected by calculating the load on the spine due to plate fixation. With the help of the “laws of theoretical mechanics,” the maximum bending moment is determined by using CLAPYRON’S THEOREM (THEOREM OF THREE MOMENTS).This project aims to use FEA/CT/CAD/CAM/RPT related technologies to substitute infected bone regions with the help of CT to CAD to STL manipulation. The paper focuses on new fabrication of artificial human bone in emergent situation by using RP technologies. Due to RP technologies, doctors and especially surgeons are privileged to do some things whichever the previous generations could only have imagined. However this is just a little step ahead. There are many unsolved medical problems and many expectations from RP in this field. This will help RP technologists to give their maximum, in such an important field like medicine.

1654

D. Chandramohan et al

Index Terms: ANSYS; Bone replacement; CT; Humerus; Mechanical Properties; Orthopaedics; Theorem of three moments; Rapid prototyping; Vertebrae.

Introduction Mechanical engineering research has explored numerous safety systems in almost all types of field. This includes the development tools such as prevention of fractures after fixation of plates. Bones are living tissue. It consists of minerals like calcium, and phosphorus. They grow rapidly during one's early years, and renew themselves. The bone is considered as a linear-elastic, isotropic, and homogeneous material. Bones are the essential part of the human skeleton. It helps to support the softer parts of the body. The project mainly deals with the injury to the shaft of humerus broken bone must be carefully fixed in position and supported until it is strong enough to bear weight. Until the last century, physicians relied on casts and splints to support the bone from outside the body (external fixation). But the development of sterile surgery extensively reduced the risk of infection so that doctors could work directly with the bone and could implant materials in the body. New materials such as stainless steel, cobalt chrome titanium and Zirconia were not only durable, but also had the strength and the flexibility necessary to support the bone. These materials are also compatible with the body and rarely cause an allergic reaction or implant failure. Currently, data are gathered using scans and X-rays, and the replacement "parts" are physically designed and reconstructed, using typical mechanical/industrial design methods and practices. Finally, on completion of the design, CNC machining codes have to be generated to allow machining of implants. Apart from the above methodology, it is also possible to construct three-dimensional (3D) models of anatomical structures based on anatomical information from scanning data such as computer tomography (CT) or magnetic resonance imaging (MRI). As it is well known, the term "rapid prototyping" refers to a number of different but related technologies that can be used for building very complex physical models and prototype parts directly from 3D CAD model. Among these technologies stereo lithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), laminated object manufacturing (LOM), inkjet-based systems and three Dimensional printing (3DP) are now becoming as the new emerging techniques.

Problem Identification Trauma is a major cause of death and disability in both developed and developing countries. The World Health Organization (WHO) predicts that by the year 2020, trauma will be the leading cause of years of life lost for both developed and developing nations. The project mainly concentrates on FRACTURES that are commonly caused due to accidents. Now a days, trauma occurs mainly due to increase in population, as well as increase in transportation, which results in an increased number of accidents that causes bone fracture in the human body. Considering the above cases, the project mainly concentrates on humerus bone fracture for the case of accident due to bike riding

Application of Advanced Design and Development

1655

which is most prevalent among the youngsters. In this humerus bone fracture there are three kinds of fracture takes place namely distal fracture, midshaft fracture and proximal fracture. From these three fracture the project mainly concentrating on the mid shaft fracture of the humerus bone. Machining of ORTHOPAEDIC ALLOY implants with high Speed Machining offers advantages but also has its own disadvantages. Mismatches can occur between real bone and implants often causing stress concentrations and premature implant failure.

Materials and Methods Biomaterials improve the quality of life for an ever increasing number of people each year. The biomaterials that contribute to the field of orthopaedics over the past decades are: Titanium, Stainless steel, Cobalt chrome and Zirconia. Orthopaedic biomaterials can be implanted into or near a bone fracture to facilitate healing or to compensate for a lack or loss of bone tissue. The materials used in orthopaedic surgery include ceramics, polymers, metals, such as stainless steel, cobalt-chromium and titanium and the shape memory alloy NiTi, and resorbable materials, such as bioglass, various modifications of hydroxyapatite and bone grafts. An implant may have bioactive effects on ossification. It may mediate recruitment of mesenchymal cells by growth factors derived from the implant, for example, a bone graft. This is called osteo induction. In addition, the implant may provide three-dimensional frames for the ingrowths of capillaries and osteoprogenitor cells. In this case, the implant has osteoconductive properties. However, metal alloy implants often give support to bone tissue without any active role in bone formation.

Characteristics of Orthopaedic Alloys Orthopaedic alloys must be very strong. They must not break or even bend permanently under heavy load. They should not be too stiff. A too stiff device will "stress shield" the skeleton too much. The orthopedic alloys are highly resistant to corrosion. Comparison of materials that are widely used in orthopaedics is shown in the table I.

Table I: Comparison of Materials. Characteristics

Stainless steel Cobalt chrome Zirconium Titanium

Stiffness

High

Medium

Medium

Low

Strength

Medium

Medium

High

High

Medium

Medium

High

Medium

Medium

High

Corrosion Low resistance Biocompatibility Low

1656


Manual Calculation The project case is mainly for youngsters during the bike riding. Assumption made V1= 60kmph, V2= 0 Mass of human body =60kg Acceleration a = (V2 – V1) / ∆ t Where V1– initial velocity V2 –final velocity ∆t – change in time a = (60/1)*(1000/3600) a =16.66 m/sec2 Then the deceleration in this condition is 16.66m/sec2 According to Newton’s second Law: Force (F) = m a So, Force F = 1000N 1000 N

270

(All dimensions are in mm) Figure 1: Stress for Bone without Plate RA* 270 = (1000*135) RA = 500N RB = 500N Maximum Bending Moment At The Mid-Shaft M (max) = (500*270)/2 = 67500N-mm Bending Stress on Solid Shaft: σь (max) = (32*M (max))/ (3.14*d³) = (32*67500)/ (3.14*22³) = 64.320 N/mm² Stress for Bone with plate (Titanium) Weight of the plate: Volume of the plate = length*width*thickness = 150*10*4.5


1657

= 6750mm3 = Area*thickness*No of holes on plate = Π *r2*t*N = 3.14*32*12*3 = 226.08mm³ = vol. of plate – vol. of screw = 6750+226.08 = 6976.08mm³ = (Net volume*Density*9.81)/le = 0.00387N/mm

Volume of screw

Net volume

Weight of the plate per meter length

1000 N

.001927 N/mm

150

270

(All dimensions are in mm) Figure 2: Stress for Bone with Plate.

Bending Stress on Solid Shaft: σь (max) = (32*M (max))/ (3.14*d³) = 65.476N/mm²

Finite Elememt Analysis Model creation of humerus bone, plate and screws is difficult to draw in ANSYS. So the following steps shown in fig.5.1 were considered to do stress Analysis on the Humerus Bone.

1658

D. Chandramohan et al SCANNING IMAGE (STL Format)

CONVERT STL to IGES (Using Pro\E)

Import to ANSYS

Analyse using ANSYS

Figure 3: Basic Steps of Analysis Process

Figure 4.1: Stress for Bone without Plate. Figure 4.2: Stress for Bone with Plate Stainless steel.

Figure 4.3: Stress for Bone with Plate Figure 4.4: Stress for Bone with Plate Cobalt chrome. Titanium.


1659

Figure 4.5: Stress for Bone with Plate Zirconia.

Table II: Comparison of Manual and Ansys Results. MATERIAL

MANUAL ANSYS (N/mm2)

BONE

64.32

74.709

STAINLESS STEEL 65.37

74.953

COBALT CHROME 65.46

75.124

TITANIUM

65.48

75.221

ZIRCONIUM

65.56

74.953

The Transfer of Forces from Shoulder Joint in To Spine Using the Theorem of Three Moments A beam, which is supported one or more than two supports, is called a continuous beam. Such a beam when loaded, will deflect with convexity upwards, over the intermediate supports, and with concavity upwards over the mid of spans. The intermediate supports of continuous beam are always subjected to bending moment.

Clapeyron’s Theorem of Three Moments It states, “If a beam has n supports , the end ones being fixed ,then the same number of equations required to determine the support moment may be obtained from the consecutive pairs of spans i.e., AB – BC – CD and so on.”

1660


(All dimensions are in mm) Figure 5: Biomechanical model of abducted upper limb. 5N

C 210

15N

B 240

19N

A 270 717 Nmm

78Nmm 519Nmm

Figure 6: Abducted upper limb is simplified in to continuous beam with ‘n’ supports.

Three Moment Equation MA * L1 + 2 * MB (L1+L2) + MC * L2 + (6 * A1 * x1) / L1 + (6 * A2 * x2) / L2 MA = 0 Mc =5 * 105 = 525 N mm Area for span BC (A2) F2 / 2 = 13 / 2 = 6.5 N = 605 * 120 = 780 N mm Area =½*b*h = ½ *240 * 780 = 93600 Nmm2 Area for span AB (A1) F1/ 2 = 19. 3/ 2 = 9.6 N Bending moment before UDL = 579.49 N mm Bending moment at mid of UDL = 1297.29 N mm Maximum bending moment at the midshaft M (max) = (26.94 * 135)


1661

= 3636.9 N-mm Solid Shaft (Humerus Bone) Subjected To Bending Only: σь (max) = (32*M (max))/(3.14*d³) = 7.7 N/mm2 Resulting moment of forces (M) applied upon the spine M = M1 A + M2 A = 7833 + 10470.483 Resultant moment of forces (M) = 8303.483Nmm Compressive vertical force (VA 2) = - 37.3 N Bending moment (max) = RB * (L1 + d) = (26.94 * 480) = 12931.2 N mm

Rehabilitation Aid for Patients A. Setting up Methodology of Motoric Therapy Focused on Exercising Upper Limbs in Osteoporotic Patients: Exclude from dynamic strengthening of UL with rubber band. Dumbbell exercises are not suitable because there is an increase of vertical compressive force upon the mechanically weakened spine in the magnitude of the sum of masses of both dumbbells. In exercises there is an increase of the magnitude of bending moment of force applied to humerus bone and spine. The bending moment and vertical compressive force are increases by the abduction of weight of the dumbbells. Strengthening of upper limb with dumbbell and lifting of weight by one upper limb represent the most unfavorable load of spine in upper limb motoric activity. B. Application of Basic Principles of motoric Activity in daily routine: The person undergone orthopaedic surgery should avoid carrying and lifting heavy weights, always carry and lift weights with both hands. While shopping, always use shopping trolleys, don’t carry shopping bags in one hand, Persons should try to be seated while travelling in public transport. When they stand and hold themselves by one hand, the impact force in case can cause sudden breaking of the implant and the force is unfavorably transferred to spine. The persons should also exclude sports straining activities (tennis, Hand ball, volley ball, etc.) which requires the effort of limbs to a greater extent. C .Benefits Of Proposed Aid: Using the proposed aid would lower costs of medicamentous therapy in acute fracture stage. Gradual adoption of the humeral musculature in the stage of acute fracture, the proposed rehabilitation aid focused at strengthening UL. It reduces the cost of long time medicamentous therapy of chronic pain.

1662


Rapid Prototyping Rapid prototyping plays a key role in the development of products. This serves as a design visualization tool as well as for fit and function application to speed up the product development. Rapid prototyping works on the basis of adding layers of material to form the desired shape. The majority of commercial rapid prototyping system build object by adding one layer after another. For simplicity, it can be visualized as stacking slices of bread until complete three-dimensional bread loaf is achieved. Rapid prototyping is a highly automated layer manufacturing process. The object is designed in any solid modeling software (CAD) and the data is converted into a standard format widely known as standard triangularisation language (STL) which is understandable by the rapid prototyping machine. Rapid prototyping software receives data in this format and creates a complete set of instructions for fabrication on rapid prototyping machine such as tool path, layer thickness, processing speed, etc. Rapid Prototyping machine then manufactures the object using layer manufacturing method. Upon completion of a three-dimensional model, it is subjected to post-processing treatment for removing support material that was used to support overhang features during fabrication. A. Fused deposition Modeling machine (FDM): The FDM process works as follows; first, a 3D solid model exported to the FDM Quick slice TM software using the STL format. The software generated the process plan that controls the FDM machine’s hardware. The concept is that an ABS filament is fed through a heating element, which heats it to a semi-molten state. FDM machine builds part by extruding a semi-molten filament through a heated nozzle onto a platform. When one layer is complete, the Platform moves down by one layer thickness and the process of extruding another layer continues. down by one layer thickness and the process of extrudi another layer continues. Heated FDM (softened) Extrusion filament Head

Direction

.

Drive Wheels

.

Liquifier Tip

Cooled platform hardens thermoplastic or wax.

Fig.7 FDM Process

Figure 7: FDM Process. After completion of all layers, the part is removed from the platform and support material can be peeled off or it can be removed by ultrasonic vibration and solvent in an


1663

ultrasonic tank. This is desirable for parts with internal cavities which are not accessible by hands. Object (Humerus Bone) to RPT

3D Sensing

3D Range Image

3D modeling Package

Meshing Model

RPT Machine

RPT model of Humerus Bone

Figure 8: Steps Involved In Rapid Prototyping.

B. Acrylonitrile Butadiene Styrene (ABS): Acrylonitrile Butadiene Styrene, chemical formula: ((C8H8· C4H6·C3H3N) n) is a common thermoplastic used to make light, rigid, molded products. ABS plastic ground down to an average diameter of less than 1 micrometer is used as the colorant in some tattoo inks. It is a copolymer made by polymerizing styrene and Acrylonitrile in the presence of polybutadiene. The proportions can vary from 15 to 35% Acrylonitrile, 5 to 30% butadiene and 40 to 60% styrene. The result is a long chain of polybutadiene criss-crossed with shorter chains of poly (styrene-co-Acrylonitrile). The nitrile groups from neighboring chains, being polar, attract each other and bind the chains together, making ABS stronger than pure polystyrene. The most important mechanical properties of ABS are resistance and toughness.

1664


Figure 9: RPT Model of Humerus Bone Using ABS material.

Conclusion The finite element model of Humerus bone of a human body has been thus created. The stress analysis of humerus bone and fixation of plate for the fractured bone has been carried out with different materials. After the bone gets fractured, orthopaedic alloy materials like Titanium, Stainless steel Cobalt chrome and Zirconia are used as a plate to reduce further fracture. After plate fixation, the stress induced on the bone with orthopedic alloy materials is calculated both manually and using ANSYS software. This project concludes that the suitable material for the plate is Titanium, when compared to other materials (results shown in tables 1 and 2) due to its high resistance to corrosion and high strength. During Adduction and Abduction of Upper limp Spine is stressed by Resultant moment of forces (M) = 18303.483 N mm compressive vertical force (VA 2) = - 37.3 N Bending moment (max) = 12931.2 N mm. An artificial bone model was fabricated using ABS (Acrylonitrile Butadiene Styrene) by Rapid Prototyping Technology. This technique helps to analyze the actual bone structure and plate fixation can be done more accurately. Due to RP technologies doctors and especially surgeons are privileged to do some things which previous generations could only have imagined. However this is just a little step ahead. There are many unsolved medical problems and many expectations from RP in this field. Development in speed, cost, accuracy, materials (especially biomaterials) and tight collaboration between surgeons and engineers is necessary and so are constant improvements from RP vendors. This will help RP technologies to give their maximum in field like medicine.

Acknowledgement I express my sincere thanks to my beloved parents for their invaluable love; moral support and constant encouragement in my life. I profoundly express my sincere thanks


1665

and heartfelt respect to my guide Dr.K.Marimuthu, Ph.D., Assistant Professor, Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore for his for giving precious suggestions and inspiring guidance thought of my research work and course study. I express my sincere thanks to my Doctoral committee members Dr.G.Sundararaj, Ph.D., Professor, Department of Production Engineering, P.S.G.College of Technology, Coimbatore and Dr.I.Rajendran, Ph.D., Professor and Head, Department of Mechanical Engineering, Dr.Mahalingam College of Engineering &Technology, Coimbatore for their valuable guidance and suggestion for this work. I own my immense gratitude to my principal Dr.V.Selladurai, Ph.D., Coimbatore Institute of Technology, Coimbatore for his moral support during the course of my Research work. Special thanks to my Wife C.Saranya with whom I shared much pain and joy. Your presence has been a big part of my feeling at home and wherever I go. Finally I thank my friends who were directly and indirectly helped me during this Research work

References [1]

[2]

[3] [4] [5]

[6]

[7]

[8]

Amir Abbas Zadpoor, “Finite element method analysis of human hand arm vibrations” Biomechanical Engineering Division, Department of Biomedical Engineering, Amirkabir University of Technology, Hafez Ave., Tehran 15914, Iran. http://www.azom.com. Azom-Metals, Ceramics, Polymers, Composites An Engineer Resource. . A to Z of Material. M.M. Bain, Eggshell strength: a mechanical/ultrastrucutral evaluation. Ph. D. Thesis, University of Glasgow, Scotland (1992). www.azom.com Biomaterials: An Overview Chryssolouris. S. Zannis, C. Derdas, K.Tsirbas, “Dimensional accuracy of FDM parts” Proceedings of the 34th International CIRP Seminar on Manufacturing Systems. Chryssolouris G., J. Kotselis, P. Koutzampoikidis, S. Zannis,D. Mourtzis, “Dimensional accuracy modelling of Stereo lithography parts” Proceedings of the 32nd CIRP International Seminar on Manufacturing Systems. Chryssolouris G., J. Kechagias P. Moustakas, E. Koutras, “Estimation of build times in Rapid Prototyping processes” Proceedings of the 8th European Conference on Rapid Prototyping and Manufacturing, Nottingham Craig M. Clemons and Daniel F. Caulfield (1994) ‘Natural fibers’ Sage Journals – Journal of Reinforced Plastics Composite s - 1354-66

1666 [9]

[10]

[11]

[12]

[13] [14]

[15]

[16]

[17]

[18] [19]

[20]

[21]

[22] [23]

D. Chandramohan et al Deniz P. AKMAN, Pynar KARAKAP, M. G.lhal BOZKIR “The Morphometric Measurements of Humerus Segments “Department of Anatomy, Faculty of Medicine, ukurova University, 01330 Adana - Turkey Hee H T,*MBBS, FRCS (Edin), FRCS (Glas), B Y Low, **FAMS, FRCS (Edin), FRCS (Glas), H F See,***FAMS, MBBS, FRCS (Glas),“Surgical results of open reduction and plating of humeral shaft fractures” Jay (Zhijijan) Zhao, Gopal Narwani, “Development of a human body finite element model for restraint system R&D applications” takata – Automotive Systems Laboratory, Inc. Paper Number 05-0399 Kechagias K J., S. Zannis, G. Chryssolouris, “Surface Roughness Modelling of the Helisys Laminated Object Manufacturing (LOM) Process” Proceedings of the 8th European Conference on Rapid Prototyping and Manufacturing, Nottingham Koniar M, Lesko M.Biomechanica (Biomechanics), Bratislava, SPN 1992, page no: 30 – 33 Lim, R. Seliktar, W.Sun, J. Holman and L. Nunes, “Finite elements (FE) modeling of the shoulder complex; a pilot study using the realistic mechanical parameters, loading and boundary conditions” Natasha M. Archer and Trace Kershaw, “Surgical implant generation network intramedullary nailing of femur & tibia fractures in rural haiti”. Department of Epidemiology & Public Health, Yale University, School of Medicine, New Haven, CT. S. Panthapulakkal, A. Zereshkian and M. Sain (2006) ‘Preparation and characterization of wheat straw fibers for reinforcing application in injection molded thermoplastic composites’ Elsevier - Bioresource Technology Volume 97, Issue 2, January 2006, Pages 265-272 Paul Wambua*, Jan Ivens, Ignaas Verpoest (2003) ‘Natural fibers: can they replace glass in fiber reinforced plastics?’ Elsevier - Composites Science and Technology 63 (2003) 1259–1264 http://www.orthobluejournal.com Parikh, Shital N. Bone Graft Substitutes in Modern Orthopedics. WENDLOVA J “Draft design of rehabilitation aid for patients with acute painful fractures of vertebrae” Department of osteological surgery, University hospital and policlinic, Bratislava, Slovakia Xiomara Bracero, Jackxander Perez, Yarielaine Rodriguez and Rebecca Ruiz, “Biomechanics of orthopaedic fixations” Applications of Engineering Mechanics in Medicine, GED – University of Puerto Rico, Mayaguez. M. Zampaloni, F. Pourboghrat, S.A. Yankovich (2007) ‘Kenaf natural fiber - A discussion on manufacturing problems and solutions’ Composites Part A: Volume 38, Issue 6 June 2007, Pages 1569-1580 http://www.efunda.com www.matweb.com