antibiotic elution from dynamic cement knee spacers

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



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Dynamic Results:High Concentration

1.0g Vancomycin,

3.6g Tobramycin



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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

antibiotic elution from dynamic cement knee spacers

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