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8/6/2019 Antibiotic Elution From Dynamic Cement Knee Spacers
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Does Cyclical Loading Affect AntibioticElution and Strength of Articulating Cement
Knee Spacers ?
BA Rogers 1, F Middleton 2, N Shearwood-Porter 3,
S Kinch 3, A Roques 4, N Bradley 5, A Taylor 4, M Browne 3
1. Mount Sinai Hospital,Toronto
2. Kingston Hospital, UK
3. School of Engineering Sciences,University of Southampton, UK
4. Aurora Orthopaedics, UK 5. Royal Surrey County Hospital, UK.
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Study Rationale
To date, little known on how cyclical fatigue loading
affects antibiotic elution from cement spacers
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Aim
To compare the differential effect of antibiotics
on in-vitro elution with static or dynamic loading
Null hypothesis
Cyclical loading of cement spacers has no
significant effect on antibiotic elution
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Sample Preparation
Hand mixed Palacos R bone cement
Biomet Stage One 70mm silicon spacer moulds
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Methodology: Specimen Preparation
4 spacers for each concentration of antibiotics were made for dynamicloading
Two spacers for each concentration were made as controls
Immersed in Phosphate buffered solution (PBS)
5ml samples of PBS taken over a set 48 hr schedule
Concentration Mass of Vancomycinper 40g cement
Mass of Tobramycin per40g cement
Low 1g 1.2g
Medium 1g 2.4gHigh 1g 3.6g
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Methodology: Dynamic Loading
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Methodology: Sampling Rate
Knee spacers immersed in solution; 3 x 5ml samples taken as per schedule
Measurement of antibiotic elution by ELISA
Time Elapsed No. of cycles
Test Control
5 minutes 0 0
2 hours 0 0
4 hours 7000 0
6 hours 14000 0
22 hours 14000 0
24 hours 21000 0
26 hours 28000 0
28 hours 35000 0
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Vancomycin Elution Control Group
Rapid initial release Levelling of concentration after ~ 400mins Vancomycin elution increases with increasing dose of tobramycin
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Tobramycin Elution Control Group
Similar profile
Tobramycin elution increases with increasing dose of tobramycin
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Dynamic Results:Low Concentration
1.0g Vancomycin,
1.0g Tobramycin
Vancomycin Release Tobramycin Release
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Dynamic Results:Medium Concentration
1.0g Vancomycin,
2.4g Tobramycin
Vancomycin Release Tobramycin Release
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Dynamic Results:High Concentration
1.0g Vancomycin,
3.6g Tobramycin
Vancomycin Release Tobramycin Release
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DiscussionThis study confirms..
Static & Dynamic Spacers
Standard elution pattern :
rapid initial antibiotic release
steady state release at 400mins
Increasing tobramycin in cement
enhances vancomycin elution
enhances tobramycin elution
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DiscussionThis study adds
Cyclical loading increases antibiotic elution
P
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Discussion
Masri et al 1, found significant increase in static elutionof vancomycin when dose of tobramycin was increased
Penner et al 2, propose passive opportunism; whereby antibiotics elute by leaking out from voids and cracks.
Tobramycin - increases void formation, and thusincreasing elution
Need further results to investigate this
1. Masri et al, 1998, J. Arthrop., 13(3), 331-338
2. Penner et al, 1996, J. Arthrop., 11(8), 939-944
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Null hypothesis
In vitro cyclical loading of cement spacers hasno significant effect on antibiotic elution
Refute for Tobramycin and Vancomycin, with
statistical significance (p
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ConclusionDynamic Cement Spacers
Mechanical and soft tissue benefits well known
This study provides evidence for the biological benefit of
articulating cement spacers in revision surgery
Future work
zirconium dioxide replaced by CaCO 3
Different antibiotic combinations or anti-fungals?
Load to failure & cement porosity
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Thank You Acknowledgements
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