Thesis Supervisor:Dr. Mukul ShuklaAssociate ProfessorMED, MNNIT, Allahabad

Surya Pratap SinghM.Tech- CAD/CAM2015CC16MED, MNNIT, Allahabad

Design & Finite Element Analysis of Lattice Structure

based Orthopaedic Implants

State-Of-Art Presentation

Department of Mechanical EngineeringMotilal Nehru National Institute of Technology, Allahabad(India)

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Content• Introduction to Area of research• Challenges in the field• Literature Review • Findings from research papers• Objective

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Introduction to orthopaedic implants

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Introduction• In orthopaedic there is a big problem

of segmental bone defect .• In segmental bone defect a long

bone is separated in two or more parts with a large gap.

• The reason behind this defect can be a high energy impact or diseases like bone cancer.

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Types of Bone Defect

Ref:https://www.studyblue.com/notes/note/n/commonly-named-skeletal-fx/deck/6147305 @10/oct/16

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X-ray Images of bone defects

Slow improvement of bone regeneration

Ref: SCOTT P. BRUDER et.al The Effect of Implants Loaded with Autologous Stem Cells on the Healing of Canine Segmental Bone Defect J Bone Joint Surg Am, 1998 Jul; 80 (7): 985 -96

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X-ray Images of bone defects

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Solutions to the problem• A general solution of this kind of

problem is use of bone plates to fix two separated bone.

• But sometimes when gap is large in bone then bone plat is not a sufficient option.

• In those cases we need a scaffold.• This scaffold can be of two types: 1. Natural 2. Artificial

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Natural Scaffolds• Natural Scaffold- also known as biological

substitutes.• In this category Autograft and Allograft are

included. Autograft (ABG- Autologous bone grafting)

A graft of tissue from one point to another of the same individual's body.

Allograft A tissue graft from a donor of the same

species as the recipient. Allograft is a good alternative to ABG

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Limitations of Natural Scaffold Autograft Limitations• The harvesting process from donor site has been

associated with perioperative and post operative complications and morbidity.

• A prolonged surgical and anaesthesiological time can cause a proportionally increased risk of infection.

• The cost of harvesting can be equivalent to the cost of commercial available bone graft

Allograft Limitations• Major risk of using allograft are viral disease transmission

and bacterial infection.• Recognized as “ Non-Self”, the allograft is attacked by the

immune system.

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Artificial ScaffoldScaffolds can be of two types

Polymer based

• Polymeric scaffolds are biodegradable but have low load bearing capacity.

• CaP, Pla ,Calcium Sulphate, Bioactive glasses are some commonly used polymeric materials.

Metal based• Metallic scaffold can bear

more load without deflection or fracture.

• Metal are not bio-degradable except Mg alloy.

• Limited metals can be used

• Ti6Al4V,Stainless steel, Co-Cr alloy, Ni-Ti alloy

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Solution for Segmental Bone Defect

a. Segmental bone defect b. Bone defect filled with metallic lattice structure c. Full view of assembly of bone plate and lattice structure

Ref: Jan Wieding et.al Finite element analysis on the biomechanical stability of open porous titanium scaffolds for large segmental bone defects under physiological load conditions “Medical Engineering & Physics 35 (2013) 422–432”

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Challenges In the Field

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Challenges in Scaffold Design

• Selection of Bio-Compatible Material• Need of Metallic Scaffold• Controlled Porosity• Compressive Strength• Patient specific implant designs• Complexity of manufacturing• Cost of manufacturing

Lattice Structure

Additive Manufacturing

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Literature Review

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Literature ReviewAreas Covered in Literature review -1. Conceptualization of bone scaffold form designing to

plantation –(8,5) 2. Stress Analysis of Femur Bone3. Properties of scaffold(5,6)4. Design Of Lattice Structure-(4,7)5. Manufacturability of Lattice Structure by using Additive

Manufacturing techniques -SLM,EBM-(2,3)6. Materials For Scaffold-(10)7. Compressive Strength analysis of scaffold-(8,11,10,3)8. Stress Analysis of bone assembled with Scaffold-(13)9. Software’s used for designing and analysis of lattice

structure-(8,11)10. Optimization of lattice structure

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Literature ReviewS.N Title Remarks Author Year

1. International Journal of Biomaterials -Next Generation Orthopaedic Implants by Additive Manufacturing Using Electron Beam Melting(Review)

•Importance of porosity in next generation implants is focused . •Manufacturability of lattice structure by Additive Manufacturing using electron beam melting technique reviewed for Ti6Al4V , and Co-Cr-Mo.

1. Lawrence E. Murr2 .Sara M. Gaytan

2016

2. Materials and Design-ElsevierSelective laser melting (SLM) of AlSi12Mg Lattice Structures

•BCC,FCC,BCCZ,FCCZ,FBCCZ truss based lattice structure are manufactured by SLM.•AlSi12Mg is selected as material for SLM.•Mechanical properties like compressive stress and young’s modulus are calculated for different structures

1.Martin Leary 2.Maciej Mazur

2016

3. Journals of Laser Applications-Mechanical response of TiAl6V4 lattice structures manufactured by selectivelaser melting in quasistatic and dynamic compression tests

•Detailed compressive testing of SLM based fbccz lattice structure is performed.•Quasistatic and dynamic tests are performed for analyis of Ti64

1. M. Brandt 2. S. Merkt

2015

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Literature ReviewS.N Title Remarks Author Year4. Computer Aided Design-

Creation of a unit block library of architectures for use in assembled scaffold engineering

•A novel method is showed for creating unit cell library.•FEA is performed for Confined compressive testing of unit cells on ABAQUS.

1.M.A.Wettergreen2.B.S.Bucklen

2005

5. Injury-Scaffold for bone healing: Concepts, materials and evidence

•Synthetic Scaffold materials are shown in this paper.•Metals, Ceramics, Bioglass , Polymers can be used as scaffold material.

1.P.Lichte2.H.C.Pape

2011

6. Injury-Tissue engineering approaches for bone repair: Concept and evidences

•Concepts like osteoinduction, osteocunduction, oseogenicity are explained .•How to increase healing process by porous design is shown

1.JoshE.Schroder2.RamiMosheiff

2011

7. Journal of Manufacturing Processes -A design for the additive manufacture of functionally graded porous structures with tailored mechanical properties for biomedical applications

•EBM based lattice structure are manufactured.•FEA is performed for mechanical properties.•Lattice structure is then applied to orthopaedic implants.

1.Jayanthi Parthasarathy 2.Binil Starly3.Shivakumar Raman

2011

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Literature ReviewS.N.

Title Remarks Author Year

8. Nature- Scientific ReportsIn vitro and in vivo study of additive manufactured porous Ti6Al4V scaffolds for repairing bone defects

•Diamond type lattice structure is used for modeling of scaffold. Manufactured by Arcam EBM machine.•In vitro and in vivo tests are performed for manufactured scaffold of Ti6Al4V.•Bone growth is shown for 3,6,12 months.

1.Guoyuan Li2. Lei Wang

2016

9. Mechanical Behavior of Biomedical Materials- Compressive behavior of bovine cancellous bone and bone analogous materials, micro CT characterization and FE analysis

•Micro C.T. is used for modeling bone like open cellular foam structure .•FEM is performed on Abaqus for mechanical testing.•AlSi7Mg and CuSn12Ni2 materails are used for manufacturing of foam

1.T.Guillen2.Q.H.Zhang

2011

10. Cell Press-Recent advances in bone tissue engineering scaffolds(Review)

•Critical issues in bone tissue engineering like- 1.biocompatibility 2. biomechanical strength 3. Metal ion release 4. biodegradation 5. Toughness are reviewed for additive manufactured scaffold

1.Susmita Bose2.Mangal Roy

2012

11. Materials Letter-A novel model for porous scaffold to match the mechanical anisotropy and structure of bone

•A novel elliptical type of lattice structure is designed for getting bone like mechanical properties. FEA of compressive testing is performed for validation.

1.Shiping Huang2.Zhou Chen

2014

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Literature ReviewS.N. Title Remarks Author Year12. Acta Biomaterialia -

Design and properties of 3D scaffolds for bone tissue engineering

•Design ,FEA and CFD is performed on 3d scaffold made by novel Voronoi tessellation Method.•Grasshopper is used for Design and Comsol is used for FEA and CFD.

1.S. Gómez 2.M.D.Vlad

2016

13. Composite Structures -Effect of structural stiffness of composite bone plate–scaffold assembly on tibial fracture with large fracture gap

•Assembled model of bone and scaffold is being analyzed in ABAQUS .•Concept of F.G.M. is used for getting optimum results.

1. Hassan Mehboob 2.Seung-Hwan Chang

2015

14. ASME- Stress analysis of bone scaffold designed for Segmental bone defects

• A honey comb lattice structure is designed in Solidworks and simulation of compressive testing is performed.•Density is changed by changing strut diameter.

1.Idriss Slaoui 2.Douglas E.Dow

2015

15. Injury-The use of bone grafts substitutes in large bone defects: Any specific needs?

•Advantages and limitations of autograft and allograft are explained.•Necessity, Materials and methods of manufacturing for synthetic scaffold is explained.•Case study for long bone union is given.

1.G.M.Calori2.E.Mazza

2011

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Conclusion from Research papers

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Conclusion from Research papers

• Idea of segmental bone defect and present recovery methods.

• Conceptualization of Next Generation orthopaedic implants

• Need of lattice structure in bone scaffold• Design and fabrication of Lattice structures• Effect of lattice structure geometry on

mechanical properties of scaffold.• Additive Manufacturing techniques for 3d

printing of lattice structure based implants

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Conceptualization

Segmental Bone Defect

ScaffoldDesign & FEA

Additive Manufacturing

Bone Implant in Human

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1.Design of Lattice Structure based Scaffold

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Why Lattice Structure?• In a new way of thinking a real bone like structure can be

generated by using lattice structural properties.• Lattice structures are light in weight , having porosity , having

sufficient strength to bear the load.

Sources: ARCAM EBM

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Concept of Unit Cells for Lattice Structure

Different types of Unit Cell

Lattice Structure by Unit cell

Ref: Volker Weißmann et.al Specific Yielding of Selective Laser-Melted Ti6Al4V Open-Porous Scaffolds as a Function of Unit CellDesign and Dimensions Metals 2016, 6, 166; doi:10.3390/met6070166

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Lattice Structure Generation• Designing• FEM Analysis- Mechanical ,Biological• .Stl file format preparation• Additive Manufacturing -SLM• SEM, Micro CT scan• Testing- Mechanical, Biological-In Vivo, In Vitro

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Designing of lattice structure

• There are four basic methods by which lattice structure’s are designed –

1. 3d geometric modeling by basic primitives

2. Implicit surface model3. Image method- micro CT

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Different Types of scaffold Modeling

Ref:S. Gómez et.al. Design and properties of 3D scaffolds for bone tissue engineering Acta Biomaterialia 42 (2016) 341–350

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2. FEA of Lattice Structure

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Study of Compressive load on Unit cell

Figure: Illustration of finite element method. (A) Unit block, seen in plane with bottom face fixed in translation in the y direction and the top face displaced in the y-direction. Subjected to 1% strain at the top face. (B) Boundary conditions applied to the unit block in the y-direction. (C) Contour plot of maximum principal stress within the architecture.

Ref:M.A.Wettergreen et.al Creation of a unit block library of architectures for use in assembled scaffold engineering Computer Aided Design-37-2005 1141-1149

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Study of Compressive behavior of Lattice Structure on confined and

unconfined testing conditionsCompressive behavior of lattice structure is investigated for confined and unconfined testing conditions.

Ref: Martin Leary et.al Selective laser melting (SLM) of AlSi12Mg lattice structures Materials and Design 98 (2016) 344–357

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Investigation of Compressive behavior of scaffold assembled with bone plate in bone

Ref: Hassan Mehboob et.al. Effect of structural stiffness of composite bone plate–scaffold assembly on tibial fracture with large fracture gap Composite Structures 124 (2015) 327–336

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3.Additive Manufacturing of Lattice Structure

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Additive Manufacturing of scaffold

Additive manufacturing of metals can be done by mainly three different techniques

1. Selective Laser Melting(SLM)2. Electron Beam Melting(EBM)3. Laser Engineered Net

Shaping(LENS)

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Metals available for scaffold

These six metals are available for additive manufacturing of scaffolds.

1. Ti6Al4V(Ti-64)2. Steel3. Cu-Co alloy 4. Ni-Ti alloy5. Tantalum6. Mg alloy

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4.Implant in human body

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Scaffold in Human Body• In vitro and In vivo tests are

performed for testing of scaffolds .• Cell proliferation, adhesion, bio- compatibility , bio-

degradability , bone regeneration are tested.

• Several animal studies are going on for the test of additively manufactured lattice structure.

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Idea of My Work- Objective

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ObjectiveDesigning Part-• Creation of unit cell library• Converting unit cells into lattice

structure with different dimensions and orientations

• Calculation of effect of unit block porosity on mechanical properties like Young’s modulus for confined and unconfined compressive testing.

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ObjectiveFEM Part-• Compressive loading behavior -Unit cell , lattice

structure• Bending behavior of lattice structure in a long bone• Calculation of stress and strain for different unit

cells in confined and unconfined compressive testing.

• FEM simulation of stress distribution, displacement, reaction force for different unit cells and lattice structures in confined and unconfined compressive testing

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References[1] Martin Leary, Maciej Mazur , Joe Elambasseril , Matthew McMillan , Thomas Chirent ,

Yingying Sun , Ma Qian , Mark Easton , Milan Brandt ,Selective laser melting (SLM) of AlSi12Mg lattice structures, Materials and Design 98 (2016) 344–357

[2] M.A. Wettergreena, B.S. Bucklen, B. Starly, E. Yuksel, W. Sun, M.A.K. Liebschner, Creation of a unit block library of architectures for use in assembled scaffold engineering, Computer-Aided Design 37 (2005) 1141–1149

[3] Lawrence E. Murr, Sara M. Gaytan,Edwin Martinez, Frank Medina, and Ryan B. Wicker, Next Generation Orthopaedic Implants by Additive Manufacturing Using Electron Beam Melting , Hindawi Publishing Corporation International Journal of Biomaterials Volume 2012, Article ID 245727, 14 pages doi:10.1155/2012/245727

[4] Volker Weißmann , Jan Wieding , Harald Hansmann , Nico Laufer , Andreas Wolf and Rainer Bader ,Specific Yielding of Selective Laser-Melted Ti6Al4V Open-Porous Scaffolds as a Function of Unit Cell Design and Dimensions Metals 2016, 6, 166; doi:10.3390/met6070166 www.mdpi.com/journal/metals

[5] Lawrence E. Murr, Edwin Martinez, Krista N. Amato, Sara M. Gaytan, Jennifer Hernandez, Diana A. Ramirez, Patrick W. Shindo, Frank Medina, Ryan B. Wicker, (R) Fabrication of Metal and Alloy Components by Additive Manufacturing: Examples of 3D Materials Science

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References[6] Jayanthi Parthasarathy ,Binil Starly,Shivakumar Raman A design for the

additive manufacture of functionally graded porous structures with tailored mechanical properties for biomedical applications Journal of Manufacturing Processes

[7] L. E. Murr, S. M. Gaytan, F. Medina, H. Lopez, E. Martinez, B. I. Machado, D. H. Hernandez, L. Martinez, M. I. Lopez, R. B. Wicker, J. Bracke Next-generation biomedical implants using additive manufacturing of complex, cellular and functional mesh arrays Advanced processing of biomaterials Published 22 March 2010.DOI: 10.1098/rsta.2010.0010 PHYLOSPHICAL Transitions of Royal Society A

[8] Susmita Bose, Mangal Roy and Amit Bandyopadhyay Recent advances in bone tissue engineering scaffolds Trends in Biotechnology, October 2012, Vol. 30, No. 10 http://dx.doi.org/10.1016/j.tibtech.2012.07.005

[9] Feng P, Wei P, Shuai C, Peng S (2014) Characterization of Mechanical and Biological Properties of 3-D Scaffolds Reinforced with Zinc Oxide for Bone Tissue Engineering. PLoS ONE 9(1): e87755. doi:10.1371/journal.pone.0087755

[10] Garrett Ryan, Abhay Pandit, Dimitrios Panagiotis Apatsidis Fabrication methods of porous metals for use in orthopaedic applications Biomaterials 27 (2006) 2651–2670

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Thank You ...

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Confined compression testing

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Objective-1

Ref:Image-10Effect of unit block porosity on apparent mechanical properties

•

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Objective-2

Uniaxial compression stress-strain responses of tested lattice specimens.Ref: Figure-11

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Objective-3

Figure:12

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Surface Name

• NS- Neovius Surface• SP- Schwarz primitive• SD- Schwarz Diamond• SG- Schwarz Gyroid• SW- Schwarz W