Biomateriales metálicos para implantes medicos y mecanismos de impresión en 3D

Metallic Biomaterials for Orthopedic Medical Devices and 3D Printing

Introduction State of Art Capabilities Conclusions

Electron Beam Melting / Introduction

Introduction State of Art Projects Capabilities Conclusions

Now a day’s cementless prosthesis become to be popular, due the optimal characteristics of bone ingrown fixation into the open cellular array in interconnected pores. In practice, they are employed on acetabula bone, columnar cages or glenoid devices.

Introduction

Conductivity in the material, pore size and pore arrangement, encourage or limit the dissemination, vascularization and nutrient transport through the porous matrix to the newly formed tissue.

The pores presented on the matrix represent the greatest influence on bone growth conditions, where the cell can enter into the pores (pore range size 100 mm to 500 mm) and proliferating creating new bone.

The Challenge of this kind of open cellular is achieve a osteoinduction, osteoconduction and osseointegration of the bone.

The main porpoise is getting a great fixation into the tissue without employ a PMMA cement fixation, that in a long term is unstable.

A major problem concerning metallic implants in orthopedic surgery is the differences between the bone Young’s modulus (10–30 GPa) and bulk metallic materials (between 110 GPa for Ti and 230 Gpa for Co–Cr alloys).

Due to this mechanical mismatch, bone is insufficiently loaded and becomes stress shielded, which eventually leads to bone resorption. It has been suggested that when bone loss is excessive, it can compromise the long-term clinical performance of the prosthesis

Problem

State of Art

Introduction State of Art Projects Conclusions

Figure 1. Image of Arcam A1

Arcam EBM

Arcam Powder Recovery System

Additive Manufacturing /Arcam EBM

AdvantagesComplexity Shapes Based Computer systems drawing

Purity Process in vacuum

environment

Capability to obtain dense and porous materials with a wide range of mechanical properties.

High Technology on biomaterials

Ti6Al4V and Co-Cr and Recovery Powder Method

Figure 2. Schematic view of the Electron Beam Melting applied

Additive Manufacturing /Arcam EBM

Figure 3. SEM micrographs of gas and water atomized metal powder

Raw Materials /Arcam EBM

Powder size between 40 and 80 mm

Figure 4. Preheated Metal Plate

Electron Beam Incident on the plate at 720° C

Electron Beam Melting /Arcam EBM

Free Form Capabilities

Introduction State of Art Aspects Conclusions

JMGranjeiro - UFF

Classificacion Anatomica del tejido óseo

Compacto o cortical

Canceloso o Esponjoso

Solids Validation

Figure 5. Solid prototype Pore and strut measurement in 2-D

Figure 6. Static tensile properties of the Ti6Al4V materials in building direction

(a) 60 mm  

(b) 60 mm Figure 10. A micrograph of (a) a longitudinal cut and (b) a

cross-sectional cut solid titanium piece.[1]

Fig. 11 SEM views of the side edge of the test component

Defects presented on Dense Titanium Alloy Pieces

Efforts to eliminate the gas voids in the EBM built samples have included standard HIP routines for Ti–6Al–4V: Thermal treatments 15 Ksi pressure at 900°C for 2 h. The present figure shows that while the voids can be largely eliminated by a single standard HIP cycle, remnants sometimes persist.

Mashes

Figure 7. (A) unit cells of designed Ti6Al4V, (B) Optical light microscopy images of the as produced scaffolds, (C) SEM Images of the as produced Ti6Al4V scaffolds and (D) 3-D Model from micro CT

data sets of the as produced Ti6Al4V scaffolds.

Figure 8. Pore and strut measurement in 2-D

Figure 9. The lattice structure of a 1,000 cell octahedron structure. (a) Model (b) actual structure.

(a)

(b)

Figura 11. Struts o ligamentos que constituyen la estructura tridimensional de la malla o esponja.

Different structures obtained by Arcam EBM

Ligaments analized

Foams

Figura 12. Modelo de esponja CAD la cual posee diferentes densidades interna y externamente, así como una vista del corte transversal de la pieza.

L.E. Murr, K.N. Amato, S.J. Li, Y.X. Tian, X.Y. Cheng, S.M. Gaytan, E. Martinez, P.W. Shindo, F. Medina, and R.B. Wicker, “Microstructure and Mechanical Properties of Open-Cellular Biomaterials Prototypes for Total Knee Replacement Implants Fabricated by Electron Beam Melting,” Journal of the Mechanical Behavior of Biomedical Materials, Volume 4, Issue 7, (2011) pages 1396-1411

Figure 13. The structure of trabecular metal (courtesy of Zimmer). See text for details.

Figure 14. Fracture plane of Duocel open-cell foam. The numbers indicate the consecutively failed struts and the stars indicate intergranular fracture.

Figure 15. (a) SE-image of a low density sample. (b) SE-image of a high density sample. Note the scale in (a) and (b).

Validation Tests for Solids

Tensile Strength

Vickers Hardness Scale

HV =1.854 L

d2

L= Load applied (Kg)d= length between angles

Angle 136°

Fig. 19 illustrates these microindentation (HV) comparisons for the solid and open-cellular structures of Ti–6Al–4V and Co–29Cr–6Mo alloy. [9]

Rockwell-C Hardness Scale

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Mechanical Testing Tensile specimens were machined from cylindrical build components, as illustrated in Figure 2, and tested in an INSTRON** 500 R tensile machine at a strain rate of 3 x 10-3 s-1, at room temperature ~293 K (20 °C)). Fracture surfaces for failed tensile specimens were also examined using FE-SEM [7].

Tensile Strenght for dense Ti6Al4V alloy based EBM

In order to evaluate the effect of sample orientation on the mechanical properties, samples were built in three different orientations: standing up, laying down flat, and lying on the side. Figure 21 shows the build orientations of the samples with respect to the start plate.

In order to validate the Arcam EBM process as an acceptable alternative to conventional fabrication methods, the mechanical properties of Ti-6Al-4V alloy samples fabricated using the Arcam EBM process were compared to Ti-6Al-4V samples fabricated by other methods such as various casting, forging, and laser deposition procedures.

Bending Test

Tests for Porous based

Density Measurement

Pore Density (ppi)

Porosity (%)

Density g/cm3

Cell Hardness (Gpa)

Stiffness (GPa)

Relative Stiffness (E/E0 * 10 -3)

Solid 1 11 55 1.99 46 9.97 90

Solid2 7 71 1.29 47 2.55 23.2

Solid 3 6 79 0.93 46 1.65 15.0

Solid 4 4 82 0.80 41 0.90 8.2

Solid 5 3 82 0.78 46 0.75 6.8

Compressive strenght/ Mesh Ti

Young’s modulus

A particularly novel application involves the manufacture of open-cellular structures with pre-selected elastic modulus or stiffness (E) for aerospace structural components, even complex heat exchangers, etc., and orthopaedic implants tailored to eliminate bone stress shielding by reducing E for high-modulus metals (such as Co-base alloys where E=210 GPa) by more than an order of magnitude.

Gibson and Ashby and Gibson have demonstrated that open-cellular structures in general are characterized by:

E = Eo(ρ/ρo)2

E: Young modulusρ: Porous material Densityρ0: Dense material Density E0 : Stiffness obteined by uniaxial compressive test Inside a Co-alloy base mesh stiffness is close to ~ 3.4GPaρ =1.9 g/cm3

ρ0=8.3 g/cm3

Microbiological / In vitro Cell Assessment employing Human Osteoblast like cells

Pore size and interconnectivity of synthetic porous biomaterials play a crucial role in bone formation. • A minimum pore size of 100–150 mm. • In some cases [2], (>300 mm) for enhanced bone

formation and the formation of capillaries.

Criteria for bone ingrowth:• Cell Size• Migration Requirements• Nutritional transport.

Human Osteoblast Like cells

Microbiological Procedures

Seeding Assessment

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Figura 69. Esquema de adherencia e integridad celular empleado para el análisis de los materiales propuestos.

Sembrado de 14000 células por ml

Previous Results

Fig. 7. DLF Ti–6Al–4V in vitro, human osteoblasts after 14 days of culturing, live/dead stain of cells on non-porous material (a) and cell culture plastic as control (b), live/dead stain of culture on porous substrate with a nominal pore diameter of 500 mm (c) and 1000 mm (d), SEM images from the same specimens (e, f). Some of the pores were filled with cells, which had grown along the pore rims in a circular-shaped manner.

Fig. 7. SEM picture of seeded cp titanium foam under static culture conditions after nine weeks (AB) and under perfusion after three weeks incubation (CF) Osteoblast under static culture condition could only be found on the outer seeded surface with SAOS cells: Broken scaffolds inside view of middle section C: SAOS cells seeded outer surface side D : Human osteoblast seeded surface side E: Human osteoblasts broken scaffold inside middle view F: SAOS cell, unseeded surface side.

(a) CAD model used for the EBM-fabrication of cp-Ti and Ti6Al4V scaffolds. (b) A photograph showing the scaffolds used in the present study. (c–h) SEM images showing the surface topography of cp-Ti (c–e) and Ti6Al4V (f–h) scaffolds at increasing magnifications; scale bar = 10 μm, 1 μm, and 100 nm, respectively.

SEM images showing hES-MPs morphology and distribution across the cp-Ti (a–d) and Ti6Al4V (e–h) scaffolds; scale bar =200 μm (a, b, d, and f) and 1 μm (c and f).

Histological micrographs of cp-Ti (a–c) and Ti6Al4V (d–f) constructs stained with toluidine blue; scale bar = 100 μm.

Structures for in vivo and mechanical analysis

Fig. 1. Anteroposterior (right) and lateral (left) radiographs of a dog showing typical position and fit of the femoral component.

Fig. 6. Digital photographs of stained (methylene blue/basic fuchsine) histological sections of 3DFT (A), BMSC 3DFT (B), 3DFT+BCP(C) and BMSC 3DFT+BCP (D) after 12 weeks of implantation on lumbar transverse processes. Bone is stained pink/red, Ti alloy black and BCP ceramic dark brown. The transverse process can be seen at the bottom of the implants and Teflon plates are visible between the implants.

Epifluorescent microscopy images of fluorochrome markers in 3DFL (A), 3DF (B), 3DFH (C), 3DFDL (D) and 3DFG (E). In all images the earliest label is green (3 weeks, calcein green), the middle label is yellow (6 weeks, oxytetracyclin) and the final label is orange (9 weeks, xylenol orange). The dark blue areas indicate scaffold.

Samples After Assessment

Transmitted light micrographs of a transverse section through a 52-week implant with small pore size. There are multiple regions of intimate bone-strut contact and evidence of a vascular supply throughout the ingrown bone

Porous scaffold dowels of Ti6Al4V were prepared and implanted into cancellous and cortical bone sites in adult sheep. Cancellous implants were examined under gap, line-to-line, and press-fit conditions, whereas line-to-line implantation was used in cortical sites. Cortical shear strength increased significantly with time and reached 26.1 ± 8.6 MPa at 12 weeks, accompanied by a concomitant increase in bone integration and remodeling.

A porous scaffold of Ti6Al4V (Regenerex; Biomet) was used in the manufacture of the implant dowels, having an average 67% porosity and pore size distribution between 100 and 600 μm.

(A and B), Methylene blue and fuchsin stain at 12 weeks at the cortical site. (A) Low-magnification overview of the exposed implant cross-section. (B) Higher-magnification image of taken at implant center. Histologic analysis demonstrated complete bone formation throughout the implant. De novo bone was in intimate contact with the implant, and no intervening fibrous tissue was observed.

Cancelous bone fill implanted in an adult sheep

Survey (to the left) and high magnification (to the right) light microscopy micrographs of tibia implants (A), (B), and (C), respectively. The bone is in close contact with the implants and, in the case of implant (C), the bone follows the irregularities of the implant surface.

Survey (to the left) and high magnification (to the right) scanning electron micrographs of implants (A), (B), and (C), respectively. Typical ridges and valleys due to machining are shown for implants (A) and (B). For implant (C), a wavy surface texture with rounded protrusions and multiple crevices

Tibia Prosthesis in rabbits

Specimens. On top the specimens for the in vivo experiment,below the specimens for the friction test. A wave structure, B cubic structure, C plasma spray coating and D sandblasted surface. (bar 10 mm)

Measurement method for bone ingrowth depth and directbone–implant contact. The arrow represents the maximumbone ingrowth depth of this quadrant. Direct bone–implantcontact was projected onto a circle representing the circumferenceof the implant in order to determine the percentage of direct bone–implant contact

Qualitative analysis of bone ingrowth. HE-stained slices of the wave (a) and cubic structure (b) with extensive bone ingrowth into the pores. Bone ingrowth on the titanium plasma sprayed (c) and sandblasted (d) control. (bar 1 mm)

Shoulder Joint Prothesis Causes and Mechanisms

Applied Knowledge of Cementless Prosthesis

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Osteoporosis, Osteoarthritis, Rheumatoid Arthritis Severe Trauma (Fracture)

Causes of Shoulder Joint Dysfunction

Main Cause: The cartilage is thinner than it is supposed to be or the bones are too weak.As a result the bones rub together causing pain, swelling and/or loss of motion of the joint. To improve the movement of the joint and to relieve the pain, a prosthesis to replace the glenoid of the shoulder joint is an option.

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In ball-and-socket joints the spherical of hemispherical head of one bone articulates with the cup-like socket of another. These joints are multiaxial and the most freely moving synovial joints. Moving is allowed in all axes and planes, including rotation.

In the shoulder, the joint sacrifice stability to provide the most freely moving joint of the body.

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Glenoid section or component loosening is the major problem of total shoulder arthroplasty. It is possible that uncemented components may be able to achieve superior fixation relative to cemented components.

Numerous all-polyethylene or metal-backed glenoid components, with keel- or peg-shaped backings, fixated either with or without cement, have been introduced in an attempt to reduce the high glenoid component loosening rate in total shoulder arthroplasty

Cemented glenoid components are limited by high stresses in the cement layer that cause damage and osteolysis, whereas cementless metal-backed components show problems with rapid polyethylene wear, component dissociation and pull out of the screws used for implant fixation. The glenoid component design is a relevant task.

Conclusions

Introduction State of Art Projects Conclusions

This studies could help us to develop a metallic biomaterials shoulder implant, creating a porous coating of the same material (Ti6Al4V or Co-Cr) with enough stability and long term fixation, to support the osseointegration.

In particular is necessary to know the thickness of the porous film formed on the implant to be removed easily the implant and at the same time reducing the risk of infection.

The final target would be, design the implants models and tools to install and remove them.

Thank you for your attention

Gracias por su atención