Inquiry
This paper provides a response to the inquiry: "How does the structure/specific property/shape of ceramic biomaterials influence their performance in hip implants?" The principal objective of coming up with the script is to analyze the existing literature on the use of ceramics as biomaterials. A lot of research is underway to optimize the use of ceramics in hip implants. The following subsections cover the literature on the effect of the shape, specific structure, and structure of ceramics as hip implants.
Introduction
Biomaterials are now an active area of research in Material Science Engineering globally. The term ‘biomaterials’ describes a wide range of materials useful for biomedical applications: Biomaterials include polymers, ceramics, metals, composites, and natural materials (Fisica, E., et al., 1999). Ceramics exhibit high corrosion resistance, high biocompatibility, low thermal and electrical conductivities, and high resistance to compressive and tensile forces. The properties make them useful as implants. The other desirable characteristic in the selection of material for use as an implant is low toxicity (Park, 1984; Krajewski & Ravaglioli, 1992).
The use of ceramics as biomaterials are due to some specific properties that emanate from their covalent and ionic bonds. Among these properties include high hardness, brittleness, fusion temperature, low chemical reactivity, and low electrical and thermal conductivities. It is worth-noting that some porous ceramic implants of hydroxyapatite (Hap) show rapid attack of adjacent connective tissues.
Literature Review
A study by Fisica et al. (2014) indicated that ceramics have certain properties that make them fit for use as hip implants. The following are some of the bioceramics the team investigated.
Materials used as hip implants
1. Calcium phosphate
A bone tissue’s inorganic phase primarily consists of calcium phosphate (Khon & Ducheyne, 2013). Phosphate salts are appropriate for use as hip implants since they are active in tissue regeneration. They take part in the tissue rejuvenation due to their structural, chemical and physical properties. Their properties are extremely similar to those of a natural bone tissue. Studies reveal that in the 1920’s, the materials were only available as powders and purely served as filling materials.
Scientists later learned that the substance enhances the creation of new bone tissues. The salts are particularly effective if the atomic ratio is in the range of 1.5 to 1.7. The success of using calcium phosphates in hip implants is dependent on several factors. Nonetheless, the chief ones include a crystalline and porous structure and the favorable atomic ratio.
2. Hydroxyapatite (HAp)
Hydroxyapatites crystallize in hexagonal systems, though purely in monoclinic systems. These compounds are effective for use as hip implants due to their chemical stability. It is critical to note that HAp is not stoichiometric in living organisms. The average ratio of HAp is approximately 1.67. The lower the ratio, the more stable the substance and the greater the biocompatibility. The underlying reactivity is also dependent on the nature of the HAp’s crystallinity.
Desirable characteristics of a ceramic hip implant
1. Structure
A hip implant must have certain elements as shown in Figure one below. The most important components include an acetabular component, a plastic liner, a femoral head, and a femoral stem.
Figure 1: Structure of a hip implant (Aherwar, et al., 2015)
Ceramic hip implants can take three possible forms: ceramic-on-polythene, ceramic-on-ceramic, or ceramic-on-metal (Dongcai et al., 2015; Wang et al., 2016). In a ceramic-on-ceramic hip implant, the ball is a ceramic and has a ceramic lining. These implants are useful for patients who won’t use the implant for repetitive impact loading. The ceramic-on-ceramic implants under considerably less wear than the rest of the types of implants. A ceramic-on-metal implant, on the other hand, has a ceramic socket with a metallic lining (Recall center, 2016). The lining received approval in 2011. The reason for its approval is that the use of the ceramic-metal combination gave a better hip than a metal-to-metal implant.
2. Specific property
One of the specific properties desired of a ceramic implant is that its mechanical properties must be compatible with those of the body. For instance, the material selected as an implant must have sufficient fatigue strength to overcome failure due to repeated loading. Biocompatibility is the second specific property desired of a ceramic implant. The implant ought to be extremely nontoxic. Toxic substances can easily cause allergic or inflammatory reactions in the body of the patient (Aherwar et al., 2015). A hip implant should also have a high corrosion and wear resistance.
3. Shape
Figure one above shows the shape of a hip implant. The implant must conform to the shape and size of the joint it is to replace. The ball must be round to prevent it from harming the neighboring bone tissues. The femur should also match with the joint under replacement. A mismatch in the shape or size of the implant would cause a long-term discomfort that would, in turn, compel a revision in the process.
Current Research
Research has been continually looking for bearings with high wear resistance. The success insertion of durable ceramic components has inspired further research in this area. Previous studies had revealed that the high use of metal-on-metal bearings had become an issue both in North America and Europe (Bozic et al., 2012). Consequently, engineers and scientists began investigating the likelihood of achieving a higher wear resistance by using a metallic acetabular liner and a ceramic head.
The implant would use mixed phase lubrication despite the unknown consequences of this combination of materials. Isaac et al. (2015) conducted a clinical study where they measured the metal ion level in the blood of a patient. After 12 months, the team compared the chromium level in a patient implanted with a metal-to-metal implant to that of a ceramic-on-metal implant. The researchers found out that the metal-metal combination had several times the amount of chromium level when compared to the ceramic-metal combination (Isaac et al., 2015).
Conclusion
Biomaterials are materials used in the replacement or repair of various body parts. A hip implant serves to replace a faulty hip joint. The material chosen for hip replacement must be biocompatible. It should also have the various desirable mechanical properties. The properties shall prevent the metal from failing regardless of the environment of use. Researchers have proved that a ceramic-on-metal hip joint is the most appropriate since toxicity level reduces when a ceramic covers a metal. The only question that lingers in the researchers’ minds is if the ceramic-to-metal combination can achieve a zero percent toxicity.
References
Fisica, E., et al. (1999). Ceramic Biomaterials: An introductory overview. Journal of Materials Education Vol.21, 21, 300. Retrieved from https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwjI8tu0yOnRAhWGro8KHZkVBLUQFgg0MAI&url=http%3A%2F%2Flapom.unt.edu%2Fpublications%2Fpdf%2520articles%2FLisa%2FSaenzJME.pdf&usg=AFQjCNFTNfmiEJxrORGI_Nr0tBo4jZzvjQ&sig2=
Park, J. B. (1984). Biomaterials Science and Engineering (2 ed., Vol. 1). New York: Plenum Press.
Krajewski, A., & Ravaglioli. (1992). Bioceramics; aterials Properties and Applications (1 ed., Vol. 2). London: Chapman and Hall.
Khon, D. H., & Ducheyne P. (2013). Materials Science and Technology: A Comprehensive Treatment: Medical and Dental Materials (Vol. 3). (D. F. Williams, Ed.) New York: VCH.
Aherwar, A., et al. (2015). Current and future biocompatibility aspects of biomaterials for hip prosthesis. AIMS Press, 2(1), 3.
Bozic K. J., et al. (2012). The epidemiology of bearing surface usage in total hip arthroplasty in the United States. Bone Joint Surgery, 2(4), 5.
Dongcai, H. D., et al. (2015). Ceramic-on-Ceramic Versus Ceramic-on-Polyethylene Bearing Surfaces in Total Hip Arthroplasty. Healio, 38(4: e331-e338), 4.
Fisica, E., et al. (1999). Ceramic biomaterials: An introductory overview. Journal of Materials Education Vol.21, 21, 300.
Isaac, G. H., et al. (2015). Ceramic-on-metal bearings in total hip replacement. Bone & Joint, 1(3), 3.
Khon, D. H., & Ducheyne P. (2013). Materials Science and Technology: A Comprehensive Treatment: Medical and Dental Materials (Vol. 3). (D. F. Williams, Ed.) New York: VCH.
Krajewski, A., & Ravaglioli. (1992). Bioceramics; aterials Properties and Applications (1 ed., Vol. 2). London: Chapman and Hall.
Park, J. B. (1984). Biomaterials Science and Engineering (2 ed., Vol. 1). New York: Plenum Press.
Recall center. (2016). In the U.S., there are currently five types of devices available, classified based on the materials used for each surface. Factors that influence how long the implant lasts depend on the needs and characteristics of the individual as well as the type of i. Hip Implants, 2, 6.
Wang, T., et al. (2016). Ceramic-on-ceramic bearings total hip arthroplasty in young patients. Science Direct, 2(4), 5.
