Effect of porosity on the osteointegration and bone ingrowth of a weight-bearing nickel–titanium bone graft substitute

Kujala, Sauli; Ryhänen, Jorma; Danilov, A.; Tuukkanen, Juha

doi:10.1016/s0142-9612(03)00359-4

Cited by 258 publications

(177 citation statements)

References 31 publications

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“…The drop of the CA was 58 lower for spark oxidized samples. The obtained increase in roughness together with the decrease in the CA suggested that these two types of treatment could possibly improve bioactivity of the surface (Kujala et al 2003;Kokubo 2005;Yi et al 2006;Yousefpour et al 2007). …”

Section: Discussionmentioning

confidence: 86%

Nanomechanical evaluation of nickel–titanium surface properties after alkali and electrochemical treatments

Chrzanowski

Neel

Armitage

et al. 2008

J. R. Soc. Interface.

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In this paper, the suitability of alkali treatment followed by heat treatment at 6008C, and spark oxidation for nickel-titanium, intended for medical applications such as pins, wires and clamps, was evaluated on the basis of nanomechanical and wear testing. In addition, the chemical composition and topography of the surface layer, wetting ability, corrosion resistance and influence of the heat treatment on structure of the alloy were also investigated. The results showed that the highest hardness was observed for alkali-treated samples, and this could be correlated with the structure of the sample that contained martensite and a higher phase transformation temperature. This treatment caused a very large increase of nickel in the top layer and decreased resistance in pitting corrosion. These results disqualified the treatment to be considered as useful for medical applications. On the other hand, the hardness of the oxidized samples was at the same level as that obtained for ground reference samples. Moreover, the oxide layer was enriched with phosphorus, and it was predominantly composed of TiO 2 and phosphorus oxides. This 3.1 mm thick layer had good adhesion to the substrate as indicated by scratch testing and wear resistant in nanowear testing. However, the oxidation did not significantly increase the corrosion resistance of the alloy compared with reference samples.

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Section: Discussionmentioning

confidence: 86%

Nanomechanical evaluation of nickel–titanium surface properties after alkali and electrochemical treatments

Chrzanowski

Neel

Armitage

et al. 2008

J. R. Soc. Interface.

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“…The scaffold is used for its osteoconductive properties [7,8] and the cells or growth factors are used for their osteoinductive or osteogenic properties [9,10]. While successful in vivo studies [11,12] and in clinical studies [13], this strategy has difficulties to settle in routine clinical practice.…”

Section: Introductionmentioning

confidence: 99%

In vivo loading increases mechanical properties of scaffold by affecting bone formation and bone resorption rates

Roshan-Ghias¹,

Lambers²,

Gholam‐Rezaee³

et al. 2011

Bone

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A successful bone tissue engineering strategy entails producing bone-scaffold constructs with adequate mechanical properties. Apart from the mechanical properties of the scaffold itself, the forming bone inside the scaffold also adds to the strength of the construct. In this study, we investigated the role of in vivo cyclic loading on mechanical properties of a bone scaffold. We implanted PLA/β-TCP scaffolds in the distal femur of six rats, applied external cyclic loading on the right leg, and kept the left leg as a control. We monitored bone formation at 7 time points over 35 weeks using time-lapsed micro-computed tomography (CT) imaging. The images were then used to construct micro-finite element models of bone-scaffold constructs, with which we estimated the stiffness for each sample at all time points. We found that loading increased the stiffness by 60% at 35 weeks. The increase of stiffness was correlated to an increase in bone volume fraction of 18% in the loaded scaffold compared to control scaffold. These changes in volume fraction and related stiffness in the bone scaffold are regulated by two independent processes, bone formation and bone resorption. Using time-lapsed micro-CT imaging and a newly-developed longitudinal image registration technique, we observed that mechanical stimulation increases the bone formation rate during 4-10 weeks, and decreases the bone resorption rate during 9-18 weeks post-operatively. For the first time, we report that in vivo cyclic loading increases mechanical properties of the scaffold by increasing the bone formation rate and decreasing the bone resorption rate.© 2011 Elsevier Inc. All rights reserved. IntroductionThe accepted paradigm in bone tissue engineering is to combine a scaffold with cells and/or growth factors [1][2][3][4][5][6]. The scaffold is used for its osteoconductive properties [7,8] and the cells or growth factors are used for their osteoinductive or osteogenic properties [9,10]. While successful in vivo studies [11,12] and in clinical studies [13], this strategy has difficulties to settle in routine clinical practice. The reasons are manifold but often related to the cost, the stringent regulations established by the regulatory authorities, the specialized infrastructure needed, or the lack of possible reimbursement from health insurances when cells or growth factors are employed.As the use of cells or growth factors is indeed the most difficult element to be included for bone tissue engineering, despite their acknowledged usefulness, we advocate a shift in the bone tissue engineering paradigm. Mechanical loading is an intrinsic stimulation present in the skeleton. It has been demonstrated in numerous in vivo studies to be correlated to bone regulation [14,15]. The in situ mechanical stimulation, if considered in an appropriate way, could then replace the cell and growth factor components of the bone tissue engineering strategy. This new paradigm has been proposed recently [16][17][18]. To support this approach, we have previously shown that controlle...

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“…38,39 Finally, the range of porosity values was limited between 50 and 90% as good in vivo osteointegration was reported for various materials with these porosities. 4,14,40,41 According to the optimization scheme, bone substitutes with elastic modulus of 500 MPa, Poisson's ratio of 0.1, and porosity of 50% are likely to maximize the proportion of fluid exchange. A 1 cm edge cubic bone substitute exchanged 10% of its fluid content with its environment during one gait cycle (Fig.…”

Section: Application To High Tibial Osteotomymentioning

confidence: 99%

Targeted mechanical properties for optimal fluid motion inside artificial bone substitutes

Blecha

Rakotomanana

Razafimahéry

et al. 2009

Journal Orthopaedic Research

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Our goal was to develop a method to identify the optimal elastic modulus, Poisson's ratio, porosity, and permeability values for a mechanically stressed bone substitute. We hypothesized that a porous bone substitute that favors the transport of nutriments, wastes, biochemical signals, and cells, while keeping the fluid-induced shear stress within a range that stimulates osteoblasts, would likely promote osteointegration. Two optimization criteria were used: (i) the fluid volume exchange between the artificial bone substitute and its environment must be maximal and (ii) the fluid-induced shear stress must be between 0.03 and 3 Pa. Biot's poroelastic theory was used to compute the fluid motion due to mechanical stresses. The impact of the elastic modulus, Poisson's ratio, porosity, and permeability on the fluid motion were determined in general and for three different bone substitute sizes used in high tibial osteotomy. We found that fluid motion was optimized in two independent steps. First, fluid transport was maximized by minimizing the elastic modulus, Poisson's ratio, and porosity. Second, the fluid-induced shear stress could be adjusted by tuning the bone substitute permeability so that it stayed within the favorable range of 0.03 to 3 Pa. Such method provides clear guidelines to bone substitute developers and to orthopedic surgeons for using bone substitute materials according to their mechanical environment. Ceramics and polymer porous structures can be produced with controlled pore size, porosity, mechanical resistance, and surface properties.1-5 Thus, novel artificial bone substitutes can be customized as to their physical properties. The question becomes which material favored best osteointegration in order to shorten the postoperative recovery phase. Much effort has been spent on searching for the optimal bone substitute architecture with regard to degradation rate and osteointegration. [6][7][8][9][10][11][12] Empirical studies show that pore interconnectivity must be >50 mm and pore diameter must be >100 mm, although this latter value is still debated. 13,14 No consensus has emerged on optimal permeability, porosity, and bulk stiffness. The need exists, therefore, to develop a synthetic approach to define target mechanical and fluid conductivity properties that likely favor osteointegration.To develop such an approach, the mechanical environment and the associated fluid motion must be considered. Many physico-chemical and biological phenomena are involved in osteointegration, but fluid motion due to mechanical loading plays a central role in bone substitute osteointegration, 15 bone mechanotransduction, 16,17 and angiogenesis. 18,19 Indeed, the transport of nutriments, wastes, biochemical signals, and cells throughout the substitute stimulates osteoblasts. 20,21 In addition, fluid motion exerts direct mechanical stress on bone cells that can stimulate 22 or damage 23 cells, depending on its magnitude. Shear stress between 0.03 and 3 Pa triggers production of essential proteins by osteobla...

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Effect of porosity on the osteointegration and bone ingrowth of a weight-bearing nickel–titanium bone graft substitute

Cited by 258 publications

References 31 publications

Nanomechanical evaluation of nickel–titanium surface properties after alkali and electrochemical treatments

Nanomechanical evaluation of nickel–titanium surface properties after alkali and electrochemical treatments

In vivo loading increases mechanical properties of scaffold by affecting bone formation and bone resorption rates

Targeted mechanical properties for optimal fluid motion inside artificial bone substitutes

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