, Volume 470, Issue 10, pp 2677-2683
Date: 03 May 2012

Mixing Method Affects Elution and Strength of High-dose ALBC: A Pilot Study

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Abstract

Background

High-dose antimicrobial-loaded bone cement (ALBC) is used to treat orthopaedic infections. High-dose ALBC is not commercially available and requires surgeon directed formulation, and there are several different methods used to mix high-dose ALBC.

Questions/purposes

We asked whether the mixing method affected antimicrobial elution and mechanical properties of high-dose ALBC.

Methods

ALBC was formulated with Simplex® P bone cement and 10 g of vancomycin per batch using one of three mixing methods: (1) hand-stirred using a standard bowl and spatula, (2) bowl-mixed using a mechanical mixing bowl, and (3) dough-phase mixing where the vancomycin was left in chunks (1–5 mm) and folded into the cement during the dough phase after adding the monomer. We eluted 45 standardized test cylinders (15 per mixing technique) for 30 days under infinite sink conditions. We tested 135 (45 per mixing method) similarly eluted cylinders in axial compression to failure.

Results

Dough-phase mixing lead to greater antimicrobial delivery, but lower compressive strength than the hand-stirred or bowl-mixed methods. Dough-phase cement released 18,570 lg of vancomycin versus 11,731 for hand-stirred and 7700 μg for bowl mixed. Compressive strength for dough-phase mixing after 30 days of elution was 36 MPa, while both hand-stirred and bowl mixed cements were 56 MPa.

Conclusions

Performance of high-dose ALBC was affected by mixing method. Dough-phase mixing led to greater antimicrobial delivery, but caused greater loss in compressive strength.

One or more of the authors received funding from the Southwest Orthopaedic Trauma Association (SWOTA) (RBM), the Herbert Louis Fund at the OREF (ACM), and Banner Good Samaritan Medical Center (RM).
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.
This work was performed at Arizona State University and Banner Good Samaritan Medical Center, Phoenix, AZ, USA.