Developing a New Generation of Bone Cements With Nanotechnology

Abstract

Around 500,000 people have total joint (including hip and knee) replacement surgeries each year. However, current joint implants last only 10 to 15 years before failing. Undoubtly because of this, many patients have to go through a revision surgery due to the failure of bone implants. The main reason for implant failure is aseptic loosening of the implant from juxtaposed bone. In this light, polymethyl methacrylate (PMMA) has been used widely in orthopedics to improve the bonding between the implant and bone. In total hip replacement procedures, PMMA cement is located at the bone-implant interface and plays an important role in inhibiting the aseptic loosening processes. PMMA cement is associated with several drawbacks that limit its efficacy (such as strong exothermic reactions, weak radiopacity and poor fatigue strength; all leading to insufficient bonding to bone). With an expectation of increased revision surgeries and patients receiving orthopedic implants in the coming years, the emphasis of joint replacement research needs to be focused on improving the mechanical and biocompatibility properties of bone cements. As nanotechnology has been extensively used to improve mechanical and surface properties of implant materials, it certainly provides a unique opportunity to modify the material properties of currently used bone cements in a more precise manner. This article reviews nanotechnology-based advancements made to PMMA cement and bioactive cements (Bis-GMA cement and calcium phosphate cement (CPC)). A discussion of accomplishments, potentials and challenges for the application of nanotechnology in bone cements then follows.

The influence of nano MgO and BaSO4 particle size additives on properties of PMMA bone cement

“…Results of the present study demonstrated that osteoblast adhesion was higher on PMMA cements with either nanophase MgO or conventional and nanophase BaSO 4 than pure PMMA cement. Results of improved osteoblast adhesion on PMMA with nanometer compared to micron particles of MgO confi rms that of other studies which have shown greater osteoblast functions on nanometer compared with conventional ceramics, metals, polymers, and composites (Liu-Synder and Webster 2007). However, future investigations will be needed to elucidate why greater osteoblast adhesion was not observed on nanometer compared with micron BaSO 4 added to PMMA.…”

“…BaSO 4 micron agglomerates serve as initiation sites for fatigue cracks. It has also been found that PMMA wear particles that contain micron-sized BaSO 4 and ZrO 2 particles cause more bone resorption than pure PMMA wear particles; this has lead to increased osteolysis when micron-sized BaSO 4 and ZrO 2 particles are used in PMMA (Liu-Synder and Webster 2007). In addition, although more testing is needed, recent studies have demonstrated less adverse reactions of ceramic nanoparticulate compared to micron wear debris (Liu-Synder and Webster 2007).…”

“…Any improvements in X-ray image contrast will not only shorten hospital stay but also reduce a patients' exposure to X-rays. X-ray exposure has been linked to increased risk of cancer (Liu-Synder and Webster 2007), thus, increased radiopacity of bone cements will allow for a reduced patients' exposure to X-rays and consequently lead to a lower incidence of cancer. Lastly, the most challenging issue associated with commercially available PMMA cements is their poor osseointegration (Glimcher 1987;Gauthier et al 1999;Barralet et al 2004;Gbureck et al 2004;Lilley et al 2005).…”

“…Perhaps sonication or other processing conditions will have to be modifi ed to amplify the degree of nanometer roughness when using nanoparticles of BaSO 4 in PMMA. Previous studies have shown greater dispersion of nanoparticles in polymers promotes osteoblast functions (Liu-Synder and Webster 2007). Furthermore, although osteoblast adhesion is a prerequisite for mineral deposition, longer-term functions of osteoblasts will have to be determined on the PMMA samples of interest to this study.…”

“…In summary, Lee and colleagues claimed in 1977 that "for the immediate future, refi nements in the technical use of [bone] cements are likely to prove more fruitful than changes in the cement itself" (Liu-Synder and Webster 2007). Over the last few decades, many modifi cations have been made to bone cements.…”