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Development and Testing of Degradable Magnesium Alloys for Bone Fracture Healing

Chaya, Amy (2016) Development and Testing of Degradable Magnesium Alloys for Bone Fracture Healing. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Abstract

Bone fractures are an extremely common injury, with over six million occurring each year in the U.S. Roughly one third of these fractures require internal fixation devices, such as plates and screws, to facilitate bone healing. Traditionally, internal fixation devices have been made with permanent metals like titanium alloys, which can cause long-term complications and even require surgical removal. To circumvent these problems, resorbable polymeric devices have been developed; however their mechanical limitations render them inadequate for many load bearing applications. Unlike permanent metals and resorbable polymers, degradable magnesium alloys provide a balance of degradation and strength. Recent investigations with magnesium alloys have begun demonstrating their promise as orthopedic biomaterials; however, additional work remains to fully assess their efficacy.
For these reasons, we conducted in vivo studies to better understand the biological effects of magnesium degradation. To begin, two subcutaneous implant models were developed incorporating human stem cells and magnesium implants. Using these models, we measured gradual magnesium degradation, and observed human cells and osteogenic protein expression around the implant-tissue interface. These results supported subsequent assessments of magnesium as fixation plates and screws using an ulna fracture model. With pure magnesium devices, we observed gradual implant degradation and fracture healing similar to that of clinically-used titanium devices. In addition, we observed abundant new bone formation around the degrading magnesium devices. Interestingly however, when testing faster degrading magnesium alloy devices, we observed localized cortical bone loss. This dichotomy in observations emphasizes the biological sensitivity to magnesium implants based on their degradation rate and composition. Taken together, our results demonstrate preliminary efficacy of pure magnesium fixation devices and support their continued development; however, additional investigations should be conducted to fully understand the mechanisms of magnesium’s effect on bone biology and long-term safety.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Chaya, Amyamychaya@gmail.comAEC28
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorSfeir, Charlescsfeir@pitt.eduCSFEIR
Committee MemberBarchowsky, Aaronaab20@pitt.eduAAB20
Committee MemberCostello, Bernard Jbjc1@pitt.eduBJC1
Committee MemberBeniash, Eliaebeniash@pitt.eduEBENIASH
Committee MemberWang, Yadongyaw20@pitt.eduYAW20
Date: 17 June 2016
Date Type: Publication
Defense Date: 18 December 2015
Approval Date: 17 June 2016
Submission Date: 22 March 2016
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 140
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Bioengineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Magnesium, bone fracture fixation, degradable metal
Date Deposited: 17 Jun 2017 05:00
Last Modified: 17 Jun 2017 05:00
URI: http://d-scholarship.pitt.edu/id/eprint/27304

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