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Failure Analysis of Biometals

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A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (15 January 2020) | Viewed by 61758

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Special Issue Editor

Dr. Reza Hashemi

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Guest Editor

College of Science and Engineering, Flinders University, Adelaide, Australia
Interests: mechanical behaviour of materials; additive manufacturing; tribology and tribocorrosion; biometals; materials testing and characterisation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Metallic biomaterials (biometals) are widely used for the manufacture of medical implants, ranging from load-bearing orthopaedic prostheses to dental and cardiovascular implants, because of their favourable combination of properties including high strength, fracture toughness, biocompatibility, wear and corrosion resistance. Additionally, they can be fabricated using well-established techniques (such as casting and forging), and recently, additive manufacturing to produce complex and customised implants. Examples of metals and metal alloys that are used for the fabrication of implants include: Ti-based alloys (e.g., Ti6Al4V and Ti6Al7Nb), Co-based alloys (e.g., CoCrMo and CoNi), austenitic stainless steels (e.g., SS316L), Zr-Nb alloys, Ni-Ti Alloys, Mg alloys, porous tantalum foams, and precious metals and alloys.

Due to the significant consequences of implant material failure/degradation, in terms of both personal and financial burden, failure analysis of biometals (in vivo, in vitro and retrieval) has been always of paramount importance in order to understand the failure mechanisms and implement suitable solutions with the aim to improve the longevity of implants in the body.

This Special Issue aims to present the latest developments and findings in the area of biometals failure. The scope includes (but is not limited to): New/advanced biometals, microstructural evaluation, mechanical properties, failure/degradation analysis, fracture, fatigue, wear, fretting wear, fretting corrosion, corrosion, in vitro and in vivo assessments, explant analysis, implant retrieval studies, biocompatibility assessments, porous biometals, surface modifications, simulations, and modelling.

Research articles, review articles, as well as communications, are invited.

Dr. Reza H Oskouei
Guest Editor

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Keywords

Biometals
Failure Analysis
In-vitro and In-vivo Assessments
Retrieval Studies
Microstructure
Fatigue and Fracture
Fretting Wear
Corrosion, Fretting Corrosion
Biotribology
Biocompatibility
Simulation and Modelling

Published Papers (11 papers)

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Editorial

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4 pages, 171 KiB

Open AccessEditorial

Failure Analysis of Biometals

by Reza Hashemi

Metals 2020, 10(5), 662; https://doi.org/10.3390/met10050662 - 19 May 2020

Cited by 3 | Viewed by 1893

Abstract

(This article belongs to the Special Issue Failure Analysis of Biometals)

Research

Jump to: Editorial, Review

15 pages, 3866 KiB

Open AccessFeature PaperArticle

Design, Modeling, Additive Manufacturing, and Polishing of Stiffness-Modulated Porous Nitinol Bone Fixation Plates Followed by Thermomechanical and Composition Analysis

by Ahmadreza Jahadakbar, Mohammadreza Nematollahi, Keyvan Safaei, Parisa Bayati, Govind Giri, Hediyeh Dabbaghi, David Dean and Mohammad Elahinia

Metals 2020, 10(1), 151; https://doi.org/10.3390/met10010151 - 19 Jan 2020

Cited by 34 | Viewed by 5013

Abstract

The use of titanium bone fixation plates is considered the standard of care for skeletal reconstructive surgery. Highly stiff titanium bone fixation plates provide immobilization immediately after the surgery. However, after the bone healing stage, they may cause stress shielding and lead to bone resorption and failure of the surgery. Stiffness-modulated or stiffness-matched Nitinol bone fixation plates that are fabricated via additive manufacturing (AM) have been recently introduced by our group as a long-lasting solution for minimizing the stress shielding and the follow-on bone resorption. Up to this point, we have modeled the performance of Nitinol bone fixation plates in mandibular reconstruction surgery and investigated the possibility of fabricating these implants. In this study, for the first time the realistic design of stiffness-modulated Nitinol bone fixation plates is presented. Plates with different levels of stiffness were fabricated, mechanically tested, and used for verifying the design approach. Followed by the design verification, to achieve superelastic bone fixation plates we proposed the use of Ni-rich Nitinol powder for the AM process and updated the models based on that. Superelastic Nitinol bone fixation plates with the extreme level of porosity were fabricated, and a chemical polishing procedure used to remove the un-melted powder was developed using SEM analysis. Thermomechanical evaluation of the polished bone fixation plates verified the desired superelasticity based on finite element (FE) simulations, and the chemical analysis showed good agreement with the ASTM standard. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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15 pages, 7943 KiB

Open AccessArticle

Biodegradable Implantation Material: Mechanical Properties and Surface Corrosion Mechanism of Mg-1Ca-0.5Zr Alloy

by Yen-Ting Chen, Fei-Yi Hung and Jie-Cheng Syu

Metals 2019, 9(8), 857; https://doi.org/10.3390/met9080857 - 06 Aug 2019

Cited by 9 | Viewed by 2673

Abstract

Mg alloy is suitable for biomedical implants as the mechanical properties of Mg are close to those of human bone. Ca is a major element in bone and Zr has a great grain refinement effect. Hence, we developed Mg-1Ca-0.5Zr alloy (XK105) as a biodegradable biomaterial and investigated its mechanical properties and surface corrosion mechanism. The results showed that heat treatment made the secondary phase homogeneous. Tensile tests showed that the heat treatment increased ductility, and that the tensile stress results in the extrusion direction showed better ductility than that in the transverse direction because of the fiber texture and extrusion characteristics. Electrochemistry test results showed that XK105 after heat treatment had a lower corrosion rate than that before heat treatment and that of pure Mg. XK105 after heat treatment formed a calcium phosphate layer after immersion in simulated body fluid; this layer protects Mg from corrosion. Surface roughening treatment increased corrosion because pits on the surface promoted pitting corrosion. This study developed Mg-1Ca-0.5Zr alloy as a biomedical implant material. The results can be used as a reference for the biomedical material industry. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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12 pages, 2610 KiB

Open AccessFeature PaperArticle

The Influence of Assembly Force on the Material Loss at the Metallic Head-Neck Junction of Hip Implants Subjected to Cyclic Fretting Wear

by Khosro Fallahnezhad, Reza H. Oskouei, Hojjat Badnava and Mark Taylor

Metals 2019, 9(4), 422; https://doi.org/10.3390/met9040422 - 08 Apr 2019

Cited by 18 | Viewed by 3408

Abstract

The impaction force required to assemble the head and stem components of hip implants is proven to play a major role in the mechanics of the taper junction. However, it is not clear if the assembly force could have an effect on fretting wear, which normally occurs at the junction. In this study, an adaptive finite element model was developed for a CoCr/CoCr head-neck junction with an angular mismatch of 0.01° in order to simulate the fretting wear process and predict the material loss under various assembly forces and over a high number of gait cycles. The junction was assembled with 2, 3, 4, and 5 kN and then subjected to 1,025,000 cycles of normal walking gait loading. The findings showed that material removal due to fretting wear increased when raising the assembly force. High assembly forces induced greater contact pressures over larger contact regions at the interface, which, in turn, resulted in more material loss and wear damage to the surface when compared to lower assembly forces. Although a high assembly force (greater than 4 kN) can further improve the initial strength and stability of the taper junction, it appears that it also increases the degree of fretting wear. Further studies are needed to investigate the assembly force in the other taper designs, angular mismatches, and material combinations. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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13 pages, 1479 KiB

Open AccessArticle

The Distribution and Severity of Corrosion Damage at Eight Distinct Zones of Metallic Femoral Stem Implants

by Roohollah Milimonfared, Reza H. Oskouei, Mark Taylor and Lucian B. Solomon

Metals 2018, 8(10), 840; https://doi.org/10.3390/met8100840 - 18 Oct 2018

Cited by 6 | Viewed by 3014

Abstract

Metallic taper junctions of modular total hip replacement implants are analysed for corrosion damage using visual scoring based on different granularity levels that span from analysing the taper holistically to dividing the taper into several distinct zones. This study aims to objectively explore the spatial distribution and the severity of corrosion damage onto the surface of metallic stem tapers. An ordinal logistic regression model was developed to find the odds of receiving a higher score at eight distinct zones of 137 retrieved stem tapers. A method to find the order of damage severity across the eight zones is introduced based on an overall test of statistical significance. The findings show that corrosion at the stem tapers occurred more commonly in the distal region in comparison with the proximal region. Also, the medial distal zone was found to possess the most severe corrosion damage among all the studied eight zones. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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24 pages, 70863 KiB

Open AccessFeature PaperArticle

Failure Analysis of PHILOS Plate Construct Used for Pantalar Arthrodesis Paper II—Screws and FEM Simulations

by Farah Hamandi, Richard Laughlin and Tarun Goswami

Metals 2018, 8(4), 279; https://doi.org/10.3390/met8040279 - 18 Apr 2018

Cited by 16 | Viewed by 8048

Abstract

A fractured stainless steel 3.5 mm proximal humerus internal locking system (PHILOS) plate and screws were investigated in this paper. This plate was used for ankle arthrodesis of a 68-year-old female with a right ankle deformity. Both the plate and screws were considered in this investigation. Optical and scanning electron microscopes (SEM) were used to document fracture surface characteristics, such as extensive scratching, plastic deformation, rubbed surfaces, discoloration, and pitting, along with cleavage, secondary cracking, deposits of debris, striations, and dimples. Indications of these features show that the plate failed by corrosion fatigue, however, overloading separated the screw(s) in two parts. Radiographic evidence shows that the screws failed ahead of the plate from the proximal end. Three-dimensional models of the plate and the screws: cortical, locking, and cannulated, were constructed using Solidworks and imported in ANSYS Workbench 16.2 to simulate the loading conditions and regions of stress development. Statistical analysis was conducted to understand the impact of different factors on the maximum von Mises stresses of the locking compression plate. These factors were the load, screw design pattern, coefficient of friction between the plate and screws, and cortical screw displacement. In summary, the finite element simulation of the plate validates the fractographic examination results. The following observations were made: (a) as the angle between the screws and the plates increased, the von Mises stresses increased in the cortical screws; and (b) the stress in the locking screws was lower than that of the cortical screws, which may be due to locking the screws with fixed angles onto the plate. Finally, fractographic examination of the cortical and locking screws supports the mechanism of corrosion-fatigue fracture from crack initiation sites, pits, due to the presence of inclusion bodies for this material (ASTM standards F138-03 and F139-03) documented for the plate in Paper I. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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19 pages, 14289 KiB

Open AccessArticle

Failure Analysis of PHILOS Plate Construct Used for Pantalar Arthrodesis Paper I—Analysis of the Plate

by Jason Ina, Madhurima Vallentyne, Farah Hamandi, Kathleen Shugart, Michael Boin, Richard Laughlin and Tarun Goswami

Metals 2018, 8(3), 180; https://doi.org/10.3390/met8030180 - 13 Mar 2018

Cited by 8 | Viewed by 5318

Abstract

The failure of a proximal humerus internal locking system (PHILOS) used in a pantalar arthrodesis was investigated in this paper. PHILOS constructs are hybrids using locking and non-locking screws. Both the plate and the screws used in the fusion were obtained for analysis. However, only the plate failure analysis is reported in this paper. The implant had failed in several pieces. Optical and scanning electron microscopic analyses were performed to characterize the failure mode(s) and fracture surface. The chemical composition and mechanical properties of the plate were determined and compared to controlling specifications to manufacture the devices. We found that equivalent tensile strength exceeded at the locations of high stress, axial, and angular displacement and matched the specification at the regions of lower stress/displacement. Such a region-wise change in mechanical properties with in vivo utilization has not been reported in the literature. Evidence of inclusions was qualitatively determined for the stainless steel 316L plate failing the specifications. Pitting corrosion, scratches, discoloration and debris were present on the plate. Fracture surface showed (1) multi-site corrosion damage within the screw holes forming a 45° maximum shear force line for crack-linking, and (2) crack propagation perpendicular to the crack forming origin that may have formed due to the presence of inclusions. Fracture features such as beach marks and striations indicating that corrosion may have initiated the crack(s), which grew by fatigue over a period of time. In conclusion, the most likely mechanism of failure for the device was due to corrosion fatigue and lack of bony in-growth on the screws that may have caused loosening of the device causing deformity and pre-mature failure. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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12 pages, 5658 KiB

Open AccessArticle

In Vitro Corrosion Assessment of Additively Manufactured Porous NiTi Structures for Bone Fixation Applications

by Hamdy Ibrahim, AhmadReza Jahadakbar, Amir Dehghan, Narges Shayesteh Moghaddam, Amirhesam Amerinatanzi and Mohammad Elahinia

Metals 2018, 8(3), 164; https://doi.org/10.3390/met8030164 - 08 Mar 2018

Cited by 65 | Viewed by 6651

Abstract

NiTi alloys possess distinct functional properties (i.e., shape memory effect and superelasticity) and biocompatibility, making them appealing for bone fixation applications. Additive manufacturing offers an alternative method for fabricating NiTi parts, which are known to be very difficult to machine using conventional manufacturing methods. However, poor surface quality, and the presence of impurities and defects, are some of the major concerns associated with NiTi structures manufactured using additive manufacturing. The aim of this study is to assess the in vitro corrosion properties of additively manufactured NiTi structures. NiTi samples (bulk and porous) were produced using selective laser melting (SLM), and their electrochemical corrosion characteristics and Ni ion release levels were measured and compared with conventionally fabricated NiTi parts. The additively manufactured NiTi structures were found to have electrochemical corrosion characteristics similar to those found for the conventionally fabricated NiTi alloy samples. The highest Ni ion release level was found in the case of 50% porous structures, which can be attributed to their significantly higher exposed surface area. However, the Ni ion release levels reported in this work for all the fabricated structures remain within the range of most of values for conventionally fabricated NiTi alloys reported in the literature. The results of this study suggest that the proposed SLM fabrication process does not result in a significant deterioration in the corrosion resistance of NiTi parts, making them suitable for bone fixation applications. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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10 pages, 1959 KiB

Open AccessArticle

Failure Analysis and Reliability of Ni–Ti-Based Dental Rotary Files Subjected to Cyclic Fatigue

by Abdullah Alqedairi, Hussam Alfawaz, Amani Bin Rabba, Areej Almutairi, Sarah Alnafaiy and Muneer Khan Mohammed

Metals 2018, 8(1), 36; https://doi.org/10.3390/met8010036 - 06 Jan 2018

Cited by 11 | Viewed by 4835

Abstract

The cyclic fatigue resistance of ProTaper Universal (PTU), ProTaper Gold (PTG), and ProTaper Next (PTN) nickel titanium (NiTi) rotary files was evaluated. Fifteen instruments of each type were selected, totaling 195 files. The instruments were rotated until fracture in an artificial canal with dimensions corresponding to the dimensions of each instrument tested: +0.1 mm in width and 0.2 mm in depth, an angle of curvature of 45°, a radius of curvature of 5 mm, and a center of curvature 5 mm from the instrument tip. The fracture surfaces of three representative samples of each subgroup were examined using scanning electron microscopy (SEM). Time to fracture was analyzed via analysis of variance and Tukey’s tests (P < 0.05). PTG F1 and F2 had significantly higher resistance than PTU F1 and PTN X2, and PTU F2 and PTN X3, respectively. PTN X2 showed a significantly higher resistance than PTU F1. The PTG series demonstrated superior cyclic fatigue (CF) behavior compared with that of the PTU and PTN series. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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Review

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17 pages, 3163 KiB

Open AccessFeature PaperReview

On the Corrosion Behaviour of Low Modulus Titanium Alloys for Medical Implant Applications: A Review

by Pooria Afzali, Reza Ghomashchi and Reza H. Oskouei

Metals 2019, 9(8), 878; https://doi.org/10.3390/met9080878 - 09 Aug 2019

Cited by 30 | Viewed by 5905

Abstract

The corrosion behaviour of new generation titanium alloys (β-type with low modulus) for medical implant applications is of paramount importance due to their possible detrimental effects in the human body such as release of toxic metal ions and corrosion products. In spite of remarkable advances in improving the mechanical properties and reducing the elastic modulus, limited studies have been done on the electrochemical corrosion behaviour of various types of low modulus titanium alloys including the effect of different beta-stabilizer alloying elements. This development should aim for a good balance between mechanical properties, design features, metallurgical aspects and, importantly, corrosion resistance. In this article, we review several significant factors that can influence the corrosion resistance of new-generation titanium alloys such as fabrication process, body electrolyte properties, mechanical treatments, alloying composition, surface passive layer, and constituent phases. The essential factors and their critical features are discussed. The impact of various amounts of α and β phases in the microstructure, their interactions, and their dissolution rates on the surface passive layer and bulk corrosion behaviour are reviewed and discussed in detail. In addition, the importance of different corrosion types for various medical implant applications is addressed in order to specify the significance of every corrosion phenomenon in medical implants. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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18 pages, 2663 KiB

Open AccessReview

3D Printed Acetabular Cups for Total Hip Arthroplasty: A Review Article

by Lorenzo Dall’Ava, Harry Hothi, Anna Di Laura, Johann Henckel and Alister Hart

Metals 2019, 9(7), 729; https://doi.org/10.3390/met9070729 - 28 Jun 2019

Cited by 62 | Viewed by 13756

Abstract

Three-dimensional (3D) printed titanium orthopaedic implants have recently revolutionized the treatment of massive bone defects in the pelvis, and we are on the verge of a change from conventional to 3D printed manufacture for the mass production of millions of off-the-shelf (non-personalized) implants. The process of 3D printing has many adjustable variables, which taken together with the possible variation in designs that can be printed, has created even more possible variables in the final product that must be understood if we are to predict the performance and safety of 3D printed implants. We critically reviewed the clinical use of 3D printing in orthopaedics, focusing on cementless acetabular components used in total hip arthroplasty. We defined the clinical and engineering rationale of 3D printed acetabular cups, summarized the key variables involved in the manufacturing process that influence the properties of the final parts, together with the main limitations of this technology, and created a classification according to end-use application to help explain the controversial and topical issues. Whilst early clinical outcomes related to 3D printed cups have been promising, in-depth robust investigations are needed, partly because regulatory approval systems have not fully adapted to the change in technology. Analysis of both pristine and retrieved cups, together with long-term clinical outcomes, will help the transition to 3D printing to be managed safely. Full article

(This article belongs to the Special Issue Failure Analysis of Biometals)

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