Mohamed Ruslan Abdullah

Biomechanical and bioactivity concepts of polyetheretherketone composites for use in orthopedic implants : a review

The use of polyetheretherketone (PEEK) composites in the trauma plating system, total replacement implants, and tissue scaffolds has found great interest among researchers. In recent years (2008 afterward), this type of composites has been examined for suitability as substitute material over stainless steel, titanium alloys, ultra high molecular weight polyethylene, or even biodegradable materials in orthopedic implant applications. Biomechanical and bioactivity concepts were contemplated for the development of PEEK orthopedic implants and a few primary clinical studies reported the clinical outcomes of PEEK-based orthopedic implants. This study aims to review and discuss the recent concepts and contribute further concepts in terms of biomechanical and bioactivity challenges for the development of PEEK and PEEK composites in orthopedic implants.

The high-velocity impact response of thermoplastic–matrix fibre–metal laminates

The high-velocity impact response of fibre metal laminates based on a woven polypropylene fibre reinforced polypropylene, termed a self-reinforced polypropylene, and a glass reinforced polypropylene has been investigated. Two types of aluminium alloy were considered, these being the 2024-O and 2024-T3 alloys. Tests on these composite–metal hybrids were undertaken using a gas gun over a wide range of incident impact energies. In this study, attention focused specifically on the perforation threshold. Following impact, the fracture mechanisms in the two types of fibre metal laminates were elucidated by sectioning and polishing samples through the point of impact and also by measuring the residual deformation of the hybrid plates. Cross-sections of the failed samples highlighted significant plasticity within the volume of these hybrid materials, indicating that considerable energy had been absorbed in plastically deforming the aluminium and composite plies. The impact resistances of the various laminates were compared by determining their specific perforation energies. Here, it was shown that fibre metal laminates based on the glass reinforced polypropylene composite offer a slightly higher perforation resistance than the self-reinforced polypropylene fibre metal laminates. Also, the fibre metal laminates based on the stronger 2024-T3 alloy out-performed their 2024-O counterparts. Finally, the perforation resistances of the fibre metal laminates were predicted using the previously reported Reid–Wen impact perforation model. Good agreement was observed between this impact model and the measured experimental data.

Effect of pretreatment process on thermal oxidation of biomedical grade cobalt based alloy

Wear on Co-Cr-Mo biomedical implants is still a major issue especially for applications in articulation joints like in total ankle, knee and hip arthroplasty. Generation of excessive wear particles can coagulate in body tissues which later cause inflammation, bone loss and necrosis. Modification of implant surfaces is a common technique for increasing the hardness and thus minimizing these effects. In this study, thermal oxidation method was carried out on the Co-Cr-Mo to investigate the effects of different pretreatment processes and surface roughness on the hardness of oxide layer formed. Prior to oxidation process, all samples were annealed and pickled to remove residual stress and oxide scales respectively. The oxidation process was done inside furnace under atmospheric condition for 3 hours at 1160 °C. The metallic compositions, surface morphology and hardness of the oxide layer formed on the substrate were verified using X-ray diffraction (XRD), scanning electron microscope and micro-Vickers hardness analysis respectively. It is found that mechanical pretreatment provides oxide/carbide layer with higher hardness than chemical pretreatment method. It is believed that remnants of polishing diamond pastes trapped in roughness valleys react with metal matrix and later transform into carbides during oxidation process. In contrast, initial surface roughness of the substrate has no significant effect on the hardness of oxide/carbide layer.

Woven Kenaf/Kevlar Hybrid Yarn as potential fiber reinforced for anti-ballistic composite material

Woven Kenaf/Kevlar Hybrid Yarn is the combination of natural and synthetic fibers in the form of thread or yarn. The yarn is weaved to form a fabric type of fiber reinforced material. Then, the fabric is fabricated with epoxy as the resin to form a hybrid composite. For composite fabrication, woven fabric Kenaf/Kevlar hybrid yarn composite was prepared with vacuum bagging hand lay-up method. Woven fabric Kenaf/Kevlar hybrid yarn composite was fabricated with total fiber content of 40 % and 60 % of Epoxy as the matrix. The fiber ratios of Kenaf/Kevlar hybrid yarn were varied in weight fraction of 30/70, 50/50 and 70/30 respectively. The composites of woven fabric Kenaf/Epoxy and woven fabric Kevlar/Epoxy were also fabricated for comparison. The mechanical properties of five (5) samples composites were tested accordingly. Result has shown that of value of strength and modulus woven fabric Kenaf/Kevlar Hybrid Yarn composite was increased when the Kevlar fiber content increased. Therefore, among the hybrid composite samples result showed the woven fabric Kenaf/Kevlar Hybrid Yarn composites with the composition of 30/70 ratio has exhibited the highest energy absorption with 148.8 J which 28 % lower than Kevlar 100 % sample. The finding indicated there is a potential combination of natural fiber with synthetic fiber that can be fabricated as the composite material for the application of high performance product.

Bioinert Metals (Stainless Steel, Titanium, Cobalt Chromium)

Stainless steel and titanium alloys are commercially used in trauma plates and screws. Stainless steel implants are being developed for corrosion resistance and biocompatibility for long-term implantation in the human body environment. Likewise, the reduction of Young’s modulus to diminish the stress shielding effects of titanium alloys implants is being investigated to promote the quality of the bone healing, particularly in osteoporotic bone fractures. In this chapter, the current challenges and methods associated with development of the stainless steel and titanium alloys materials for use in trauma plating systems (plate and screws) are reviewed and discussed. Because cobalt chromium alloys (CoCr) have been recently utilized as screws in combination with titanium plates, the associated concepts related to this material for use in trauma plating systems are also reviewed.

Experimental and Numerical Studies of Fiber Metal Laminate (FML) Thin-Walled Tubes Under Impact Loading

Fiber metal laminate (FML) in form of tubular structures is a modern light-weight structure fabricated by incorporating metallic and composite materials. This present study deals with the impact characteristics and energy absorption performances of fiber metal laminate (FML) thin-walled tubes subjected to impact loading. Dynamic computer simulation techniques validated by experimental testing are used to perform a series of parametric studies of such devices. The study aims at quantifying the crush response and energy absorption capacity of FML thin-walled tubes under axial impact loading conditions. A comparison has been done in terms of crush behaviour and energy absorption characteristics of FML tubes with that of pure aluminium and composite tubes. It is evident that FML tubes are preferable as impact energy absorbers due to their ability to withstand greater impact loads, thus absorbing higher energy. Furthermore, it is found that the loading capacity of such tubes is better maintained as the crush length increases. The primary outcome of this study is design information for the use of FML tubes as energy absorbers where impact loading is expected particularly in crashworthiness applications.

Effect of a coupling agent on mechanical and biological properties of polyetheretherketone/hydroxyapatite bioactive composite for prosthetic medical evice

For many years, research was focused on developing a medical part of human body from polymer as to replace metal. In this study, the aim is to produce a Polyetheretherketone/Hydroxyapatite (PEEK/HA) composite which posses balance mechanical properties and good spreading of bioactive ceramic, hydroxyapatite. The composite consist of 10-30 wt% HA were compounded via nano-single screw extruder and sample for testing were produced by injection molding. Each formulation of HA was treated with (3-Aminopropyl)trimethoxysilanes coupling agent to compare with untreated HA. The result showed that the slight increasing value of Elastic modulus, flexural strength, tensile strength while decreasing flexural modulus for 10 and 20 wt% HA compared to untreated composite. The enhance of bioactivity has been proven with the incorporation of HA into PEEK. SEM-EDX image showed the bulk formation of apatite layers on the composite surface with 30 wt% HA after 3 days immersed in SBF solution. Finally, these composite be capable of being one of the biomedical part seing as the mechanical properties were found to be within the properties of human cortical and cancellous bone.

Bioinert Polymers (Polyetheretherketone)

Polyetheretherketone (PEEK) is a newly developed polymer with good biocompatibility characteristics. The biomechanical and biological advantages of the PEEK polymer make it a promising material for the development of composites for orthopedic implants. Some of the PEEK advantages include the similarity of mechanical properties of PEEK compared with human bone tissue; lack of electrochemical activity in vivo; excellent corrosion resistance and biocompatibility; considerable fatigue strength; wear resistance; tensile strength, compressive strength, and ductility. All these superior characteristics have motivated biomechanical and biomaterial researchers and orthopedic manufacturers to develop the PEEK polymer in combination with other fillers such as carbon fiber, hydroxyapatite, etc. to promote the mechanical and biological benefits of the PEEK polymer for use in orthopedic implants. In this chapter, the biomechanical and biological concepts that have been considered in the possible development of PEEK medical implants are reviewed and discussed. The potential usage of PEEK and its composites are then reviewed in conjunction with their biomechanical and biological benefits compared to the current metallic implants. The biomechanical challenges of using PEEK composites, particularly carbon fiber reinforced polyetheretherketone (CFRPEEK) in trauma plating systems are examined and further evaluation concepts are discussed.

Biodegradable Metals (Biodegradable Magnesium Alloys)

In this chapter, the recent developments of biodegradable magnesium alloys are reviewed. These materials are promising for use in trauma plating fixation. The main challenge of magnesium alloy is the biodegradation rate of the material in human body fluid. Recently, various methods have been utilized to promote the corrosion resistance of magnesium alloys in an in vivo environment. However, it is still controversial among the researchers how the degradation rate of magnesium alloy could be reduced to obtain sufficient mechanical stability of fracture fixation in treatment of trauma injuries. Due to fast degradation of magnesium alloy it will be very challenging to reduce the degradation rate. Methods developed for reduction of the magnesium degradation rate could affect biocompatibility, cytocompatibility, and mechanical strength of the magnesium alloy implant in vivo environment. The challenges and promising aspects of magnesium alloys are reviewed and discussed in this chapter. In Chapter 16, Further Development of Trauma Plating Fixation, the possible exploration of magnesium alloys for use in trauma plating fixation is presented.

Biomechanical Evaluation Methods

Biomechanical evaluation methods are carried out based on simulation of the bone-implant fracture fixation with consideration of adequate physiological boundary and loading conditions. Experimental testing and computer aided engineering (CAE) methods have been developed to evaluate the mechanical safety of the trauma plating systems. Experimental testing methods have been greatly utilized to evaluate the mechanical behavior of the bone-plate fracture fixation under various loading conditions, while CAE methods have not been considerably used for biomechanical evaluation of trauma plating fixation. In this chapter, the fundamentals, challenges, limitations, advantages, and disadvantages of experimental and CAE methods for use in biomechanical evaluation of trauma plating systems are reviewed and discussed. Utilization of biomechanical evaluation methods in conjunction with understanding of the clinical requirements for plating fixation of the bone fractures is beneficial for effective design and development of the trauma plating system which is reviewed in Section IV of the book. Therefore, this chapter is recommended as a prerequisite for Section IV. Likewise, new ideas for development of biomechanical evaluation methods are presented in Section V, thereby reading of this chapter is considered as essential prerequisite for Section V.