Characteristics of bone ingrowth and interface mechanics of a new porous tantalum biomaterial. J Bone Joint Surg 81-B:907-914

Montreal General Hospital and McGill University, Québec, Canada.
The Bone & Joint Journal (Impact Factor: 3.31). 10/1999; 81(5):907-14. DOI: 10.1302/0301-620X.81B5.9283
Source: PubMed


We have studied the characteristics of bone ingrowth of a new porous tantalum biomaterial in a simple transcortical canine model using cylindrical implants 5 x 10 mm in size. The material was 75% to 80% porous by volume and had a repeating arrangement of slender interconnecting struts which formed a regular array of dodecahedron-shaped pores. We performed histological studies on two types of material, one with a smaller pore size averaging 430 microm at 4, 16 and 52 weeks and the other with a larger pore size averaging 650 microm at 2, 3, 4, 16 and 52 weeks. Mechanical push-out tests at 4 and 16 weeks were used to assess the shear strength of the bone-implant interface on implants of the smaller pore size. The extent of filling of the pores of the tantalum material with new bone increased from 13% at two weeks to between 42% and 53% at four weeks. By 16 and 52 weeks the average extent of bone ingrowth ranged from 63% to 80%. The tissue response to the small and large pore sizes was similar, with regions of contact between bone and implant increasing with time and with evidence of Haversian remodelling within the pores at later periods. Mechanical tests at four weeks indicated a minimum shear fixation strength of 18.5 MPa, substantially higher than has been obtained with other porous materials with less volumetric porosity. This porous tantalum biomaterial has desirable characteristics for bone ingrowth; further studies are warranted to ascertain its potential for clinical reconstructive orthopaedics.

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Available from: Michael Tanzer, Oct 10, 2015
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    ABSTRACT: Although the contact pressure increases during implantation of a wedge-shaped implant, friction coefficients tend to be measured under constant contact pressure, as endorsed in standard procedures. Abrasion and plastic deformation of the bone during implantation are rarely reported, although they define the effective interference, by reducing the nominal interference between implant and bone cavity. In this study radial forces were analysed during simulated implantation and explantation of angled porous and polished implant surfaces against trabecular bone specimens, to determine the corresponding friction coefficients. Permanent deformation was also analysed to determine the effective interference after implantation. For the most porous surface tested, the friction coefficient initially increased with increasing normal contact stress during implantation and then decreased at higher contact stresses. For a less porous surface, the friction coefficient increased continually with normal contact stress during implantation but did not reach the peak magnitude measured for the rougher surface. Friction coefficients for the polished surface were independent of normal contact stress and much lower than for the porous surfaces. Friction coefficients were slightly lower for pull-out than for push-in for the porous surfaces but not for the polished surface. The effective interference was as little as 30% of the nominal interference for the porous surfaces. The determined variation in friction coefficient with radial contact force, as well as the loss of interference during implantation will enable a more accurate representation of implant press-fitting for simulations. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Journal of Biomechanics 07/2015; DOI:10.1016/j.jbiomech.2015.07.012 · 2.75 Impact Factor
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    Biomaterials 10/2014; 37. DOI:10.1016/j.biomaterials.2014.10.027 · 8.56 Impact Factor
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    • "Intensive efforts have been made to determine the most adequate composition and architecture. On the chemical side, many materials varying in composition and architecture have been proposed, including polymers (Ishaug-Riley et al., 1997; Ignatius et al., 2001; Mondrinos et al., 2006; Gogolewski et al., 2008), metals (Ayers et al., 1999; Bobyn et al., 1999; Itala et al., 2001; Witte et al., 2007) and ceramics (Klawitter and Hulbert, 1971; Klein et al., 1985; van Blitterswijk et al., 1986; Eggli et al., 1988; Daculsi and Passuti, 1990; Schliephake et al., 1991; Basle et al., 1993; Metsger et al., 1993; Lu et al., 1999; Flautre et al., 2001; Walsh et al., 2003; Jones and Hench, 2004; Linhart et al., 2004; Hench, 2006; Von Doernberg et al., 2006; Mastrogiacomo et al., 2007; Lan Levengood et al., 2010; Murakami et al., 2010; Yuan et al., 2010; Polak et al., 2011; Haugen et al., 2013). These materials present very different resorption rates, and many resorption mechanisms, such as dissolution, hydrolysis (e.g., poly(α-hydroxy acids) (Ignatius et al., 2001)), cell-mediated resorption (Basle et al., 1993; Lu et al., 1999; Von Doernberg et al., 2006; Yuan et al., 2010), corrosion (Witte et al., 2007), enzymatic degradation (Hutmacher, 2000; Vert, 2007), and transport (Vert, 2007). "
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