Nanocomposite bone cements for orthopaedic applications

Poly methylmethacrylate (PMMA) is the principal component of orthopaedic bone cement. However, it is susceptible to fatigue-related cracking or impact-induced failure. We have previously reported that adding MWCNTs (Multi Walled Carbon Nanotubes)(0.1wt.%) significantly improved the mechanical performance of PMMA-based bone cements and reduced the thermal necrosiscaused by the exothermic curing reaction of the cement [1].However, the effect of MWCNTs of various loading (wt.%) and functionality has yet to be considered. Recently there have been increased efforts to determine the effects of nanosized materials in vivo, with a particular emphasis on tracking their movement. Attachment of radioactive metal ions to MWCNTs via a bi-functional caged ligand would potentially allow for labelling and tracking. The objective of this study was to investigate the effect of MWCNT loading and functionality on mechanical, thermal and rheological properties of PMMA cements. In addition a method for radiolabelling MWCNTs has also been investigated Unfunctionalised, carboxyl (–COOH) functionalised and amine(–NH2) functionalised MWCNTs (Nanocyl S.A., Belgium) at varied wt% loadings (0.1, 0.25, 0.5, and 1.0) were incorporated into ColacrylB866 (Lucite International Ltd., UK) bone cement. Static mechanical properties were measured in accordance with ISO 5833:2002 [2].The plane strain fracture toughness was determined using Chevron-Notch Short Rod method [3]. The fatigue properties of the cements were determined in tension – tension with a lower stress of 0.3 MPa and an upper stress of 22.0 MPa being applied at a frequency of2 Hz [4]. Rheology was used to determine the time at which the onset of cure (tons) occurred and the critical gelation time (gel-time). Radioactive labelling of –COOH functionalised MWCNTs with gamma emitting 57Co (T1/2= 270 days) was completed using a bi-functional cage ligand (MeAMN3S3sar).Incorporating MWCNTs (≤0.25wt%) into cement significantly (p-value<0.001) improved the static and dynamic mechanical properties. However greater loadings of MWCNTs did not provide any further improvements and in some cases resulted in significant(p-value<0.001) reductions in mechanical properties. The extent of this effect was dictated by MWCNT functionality and the wt% used. Improvements were attributed to the MWCNTs arresting crack propagation. The exothermic polymerisation reaction for the PMMA cement was significantly reduced when thermally conductive MWCNTs were added. This was supported by the rheological characterisation as adding MWCNTs significantly altered tons and gel-time. The potential to radioactively label MWCNTs was successfully demonstrated, and further work will be conducted to assess the biological implications by tracking the radiolabelled MWCNTs under in vivo conditions. © 2006 Elsevier Ltd.

Keywords

Cements, Skeleton, Composite materials, Uses, Mechanics, Implants

Citation

Dunne, N., Ormsby, R., McNally, T., Mitchell, C. A., Martin, D., Halley, P., Nicholson, T., Schiller, T., Gahan, L., Musumeci, A, & Smith, S. V. (2010). Nanocomposite bone cements for orthopaedic applications. Paper presetned to the International Conference on Orthopaedic Biomechanics, Clinical Applications and Surgery (OBCAS 2010), 6th - 9th June 2010. Brunel University: London, United Kingdom. In Journal of Biomechanics, 43(S1), S53. doi:10.1016/S0021-9290(10)70112-3