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Postgraduate Thesis: The development of magnesium-based materials for orthopaedic applications
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TitleThe development of magnesium-based materials for orthopaedic applications
 
AuthorsWong, Hoi-man.
黃凱文.
 
Issue Date2011
 
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
 
AbstractThe currently used biomaterials for surgical implantation include stainless steel, titanium and its alloys. However, due to the non-degradability and the mismatch of the mechanical properties between these metallic implants and human bone, there maybe a long-term adverse effect of inflammation or stress shielding effect. This may lead to bone loss which brings with a higher risk of implant failure. To avoid this problem, implants made of biodegradable materials are the alternatives. Due to the poor mechanical properties of biodegradable polymer especially for load-bearing area, biodegradable metal is used instead. Magnesium is the potential candidate since it is degradable with mechanical properties similar to human bone whilst magnesium ion is an essential element to human bodies. With the advantages of using magnesium for implantations, it can be potentially used for fracture fixation implant and bone substitutes. However, its rapid degradation and release of hydrogen gas may inhibit its use. Hence, modification is required. In this project, plasma immersion ion implantation and deposition (PIII&D) using aluminium oxide as the plasma source was conducted on the magnesium alloys. The corrosion resistance properties of the plasma-treated magnesium alloy were found to display significant improvement in immersion test especially at early time points. The plasma-treated sample was compatible with osteoblasts. Cells attached and grew on the treated sample but not the untreated sample. The animal study showed consistent results with the cell study, and there was a significant increase in bone formation around the treated sample when compared to the untreated sample. The other potential application of magnesium is its usage as a bone substitute. Due to the limitations of autografts and allografts, synthetic bone substitutes are developed. The ideal bone substitutes should have similar properties to those found with autografts. However, no such bone substitutes presently exist; hence, a novel hybrid material is fabricated in this project through the addition of magnesium granules into a biodegradable polymer polycaprolactone (PCL). The immersion test showed that an apatite layer composed of magnesium, calcium, phosphate and hydroxide was formed on the hybrids but not on pure PCL, which suggested that the hybrids were osteoinductive and osteoconductive. The compression test showed that the mechanical properties were enhanced with the incorporation of magnesium granules into pure PCL and were still maintained after 2 months of immersion. Osteoblasts grew well on the PCL-Mg hybrids. The addition of smaller amounts of magnesium granules (0.1g PCL-Mg) resulted in higher ALP activity and up-regulation of different bone markers when compared to the pure PCL. Finally, the animal studies showed that more new bone formation was found around the 0.1g PCL-Mg hybrids especially at early time points, which suggested that the healing time could be shortened. In conclusion, fracture fixation implants and novel bone substitutes based on magnesium were developed in this project. The aluminium oxide coating was able to improve the corrosion resistance properties of magnesium alloy by suppressing the release of magnesium ions. The PCL-Mg hybrids were found to be biodegradable, biocompatible, osteoconductive, osteoinductive and mechanically matched to human bone properties.
 
AdvisorsYeung, KWK
Cheung, KMC
Luk, KDK
 
DegreeDoctor of Philosophy
 
SubjectMetals in medicine.
Magnesium alloys.
Orthopedic implants.
Bone substitutes.
 
Dept/ProgramOrthopaedics and Traumatology
 
DC FieldValue
dc.contributor.advisorYeung, KWK
 
dc.contributor.advisorCheung, KMC
 
dc.contributor.advisorLuk, KDK
 
dc.contributor.authorWong, Hoi-man.
 
dc.contributor.author黃凱文.
 
dc.date.hkucongregation2012
 
dc.date.issued2011
 
dc.description.abstractThe currently used biomaterials for surgical implantation include stainless steel, titanium and its alloys. However, due to the non-degradability and the mismatch of the mechanical properties between these metallic implants and human bone, there maybe a long-term adverse effect of inflammation or stress shielding effect. This may lead to bone loss which brings with a higher risk of implant failure. To avoid this problem, implants made of biodegradable materials are the alternatives. Due to the poor mechanical properties of biodegradable polymer especially for load-bearing area, biodegradable metal is used instead. Magnesium is the potential candidate since it is degradable with mechanical properties similar to human bone whilst magnesium ion is an essential element to human bodies. With the advantages of using magnesium for implantations, it can be potentially used for fracture fixation implant and bone substitutes. However, its rapid degradation and release of hydrogen gas may inhibit its use. Hence, modification is required. In this project, plasma immersion ion implantation and deposition (PIII&D) using aluminium oxide as the plasma source was conducted on the magnesium alloys. The corrosion resistance properties of the plasma-treated magnesium alloy were found to display significant improvement in immersion test especially at early time points. The plasma-treated sample was compatible with osteoblasts. Cells attached and grew on the treated sample but not the untreated sample. The animal study showed consistent results with the cell study, and there was a significant increase in bone formation around the treated sample when compared to the untreated sample. The other potential application of magnesium is its usage as a bone substitute. Due to the limitations of autografts and allografts, synthetic bone substitutes are developed. The ideal bone substitutes should have similar properties to those found with autografts. However, no such bone substitutes presently exist; hence, a novel hybrid material is fabricated in this project through the addition of magnesium granules into a biodegradable polymer polycaprolactone (PCL). The immersion test showed that an apatite layer composed of magnesium, calcium, phosphate and hydroxide was formed on the hybrids but not on pure PCL, which suggested that the hybrids were osteoinductive and osteoconductive. The compression test showed that the mechanical properties were enhanced with the incorporation of magnesium granules into pure PCL and were still maintained after 2 months of immersion. Osteoblasts grew well on the PCL-Mg hybrids. The addition of smaller amounts of magnesium granules (0.1g PCL-Mg) resulted in higher ALP activity and up-regulation of different bone markers when compared to the pure PCL. Finally, the animal studies showed that more new bone formation was found around the 0.1g PCL-Mg hybrids especially at early time points, which suggested that the healing time could be shortened. In conclusion, fracture fixation implants and novel bone substitutes based on magnesium were developed in this project. The aluminium oxide coating was able to improve the corrosion resistance properties of magnesium alloy by suppressing the release of magnesium ions. The PCL-Mg hybrids were found to be biodegradable, biocompatible, osteoconductive, osteoinductive and mechanically matched to human bone properties.
 
dc.description.naturepublished_or_final_version
 
dc.description.thesisdisciplineOrthopaedics and Traumatology
 
dc.description.thesisleveldoctoral
 
dc.description.thesisnameDoctor of Philosophy
 
dc.identifier.hkulb4786954
 
dc.languageeng
 
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)
 
dc.relation.ispartofHKU Theses Online (HKUTO)
 
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.
 
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License
 
dc.source.urihttp://hub.hku.hk/bib/B47869549
 
dc.subject.lcshMetals in medicine.
 
dc.subject.lcshMagnesium alloys.
 
dc.subject.lcshOrthopedic implants.
 
dc.subject.lcshBone substitutes.
 
dc.titleThe development of magnesium-based materials for orthopaedic applications
 
dc.typePG_Thesis
 
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<item><contributor.advisor>Yeung, KWK</contributor.advisor>
<contributor.advisor>Cheung, KMC</contributor.advisor>
<contributor.advisor>Luk, KDK</contributor.advisor>
<contributor.author>Wong, Hoi-man.</contributor.author>
<contributor.author>&#40643;&#20977;&#25991;.</contributor.author>
<date.issued>2011</date.issued>
<description.abstract>&#65279;The currently used biomaterials for surgical implantation include stainless

steel, titanium and its alloys. However, due to the non-degradability and the

mismatch of the mechanical properties between these metallic implants and

human bone, there maybe a long-term adverse effect of inflammation or stress

shielding effect. This may lead to bone loss which brings with a higher risk of

implant failure. To avoid this problem, implants made of biodegradable

materials are the alternatives. Due to the poor mechanical properties of

biodegradable polymer especially for load-bearing area, biodegradable metal is

used instead. Magnesium is the potential candidate since it is degradable with

mechanical properties similar to human bone whilst magnesium ion is an

essential element to human bodies.

With the advantages of using magnesium for implantations, it can be

potentially used for fracture fixation implant and bone substitutes. However, its

rapid degradation and release of hydrogen gas may inhibit its use. Hence,

modification is required. In this project, plasma immersion ion implantation

and deposition (PIII&amp;D) using aluminium oxide as the plasma source was

conducted on the magnesium alloys. The corrosion resistance properties of the

plasma-treated magnesium alloy were found to display significant

improvement in immersion test especially at early time points. The

plasma-treated sample was compatible with osteoblasts. Cells attached and

grew on the treated sample but not the untreated sample. The animal study

showed consistent results with the cell study, and there was a significant

increase in bone formation around the treated sample when compared to the

untreated sample.

The other potential application of magnesium is its usage as a bone

substitute. Due to the limitations of autografts and allografts, synthetic bone

substitutes are developed. The ideal bone substitutes should have similar

properties to those found with autografts. However, no such bone substitutes

presently exist; hence, a novel hybrid material is fabricated in this project

through the addition of magnesium granules into a biodegradable polymer

polycaprolactone (PCL). The immersion test showed that an apatite layer

composed of magnesium, calcium, phosphate and hydroxide was formed on the

hybrids but not on pure PCL, which suggested that the hybrids were

osteoinductive and osteoconductive. The compression test showed that the

mechanical properties were enhanced with the incorporation of magnesium

granules into pure PCL and were still maintained after 2 months of immersion.

Osteoblasts grew well on the PCL-Mg hybrids. The addition of smaller

amounts of magnesium granules (0.1g PCL-Mg) resulted in higher ALP

activity and up-regulation of different bone markers when compared to the

pure PCL. Finally, the animal studies showed that more new bone formation

was found around the 0.1g PCL-Mg hybrids especially at early time points,

which suggested that the healing time could be shortened.

In conclusion, fracture fixation implants and novel bone substitutes based

on magnesium were developed in this project. The aluminium oxide coating

was able to improve the corrosion resistance properties of magnesium alloy by

suppressing the release of magnesium ions. The PCL-Mg hybrids were found

to be biodegradable, biocompatible, osteoconductive, osteoinductive and

mechanically matched to human bone properties.</description.abstract>
<language>eng</language>
<publisher>The University of Hong Kong (Pokfulam, Hong Kong)</publisher>
<relation.ispartof>HKU Theses Online (HKUTO)</relation.ispartof>
<rights>The author retains all proprietary rights, (such as patent rights) and the right to use in future works.</rights>
<rights>Creative Commons: Attribution 3.0 Hong Kong License</rights>
<source.uri>http://hub.hku.hk/bib/B47869549</source.uri>
<subject.lcsh>Metals in medicine.</subject.lcsh>
<subject.lcsh>Magnesium alloys.</subject.lcsh>
<subject.lcsh>Orthopedic implants.</subject.lcsh>
<subject.lcsh>Bone substitutes.</subject.lcsh>
<title>The development of magnesium-based materials for orthopaedic applications</title>
<type>PG_Thesis</type>
<identifier.hkul>b4786954</identifier.hkul>
<description.thesisname>Doctor of Philosophy</description.thesisname>
<description.thesislevel>doctoral</description.thesislevel>
<description.thesisdiscipline>Orthopaedics and Traumatology</description.thesisdiscipline>
<description.nature>published_or_final_version</description.nature>
<date.hkucongregation>2012</date.hkucongregation>
<bitstream.url>http://hub.hku.hk/bitstream/10722/161513/1/FullText.pdf</bitstream.url>
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