Modification of Glass Poly(alkenoate) Cement for Revision Total Knee Arthroplasty

Abstract

<p>Poly(methyl methacrylate) (PMMA) bone cement is employed as a void filler in revision total knee arthroplasty (rTKA). The first phase of this thesis investigates the role of PMMA in managing bone loss and infection in rTKA. Treating bone defects with PMMA can result in complications such as bone necrosis and implant loosening. Additionally, toxicity, roughness, and bacterial colonization on PMMA surface were identified as some complications of using antibiotic-impregnated PMMA spacers in rTKA. These concerns are driving the development of alternative bone cements. </p> <p>The second phase of this thesis relates to the modification of glass polyalkenoate cement (GPC) for use in rTKA. Modified GPCs (mGPCs) based on the glass system SiO<sub>2</sub>-ZnO2CaO-SrO-P<sub>2</sub>O<sub>5</sub>-X TA<sub>2</sub>O<sub>5 </sub>containing 1, 5, and 15 wt.% calcium sulfate (CaSO<sub>4</sub>) were characterized. Working and setting times, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), pH, ion release, compressive strength and biaxial flexural strength (BFS) of each composition were assessed. The mGPCs were found to have a shorter setting time, higher initial compressive strength, and ion release than the control GPC (naive of CaSO<sub>4</sub>). Moreover, CaSO<sub>4 </sub>addition led to the formation of pores on the surface of GPC which can increase osseointegration. </p> <p>In the next phase, the <em>in vivo</em> properties of two GPCs (GPCA and GPCB) were evaluated using three sheep. After comparing handling, compressive strength, ion release and cytotoxicity results of each GPC formulation, three sets of GPCA samples were used for implantation. Clinical CT scans and Micro-CT images obtained at 0, 6 and 12 weeks revealed the varied radiological responses of sheep bone to GPCA. Excessive Zn<sup>2+</sup> ion release and low pH were identified as possible causes of the resorption surrounding some GPCA implants. Further investigation on modifying GPC formulations with the focus on reducing the rate of Zn<sup>2+</sup> release and pH is required.</p>