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Bettlach, Switzerland

Bashoor-Zadeh M.,Universite de Sherbrooke | Baroud G.,Universite de Sherbrooke | Bohner M.,RMS Foundation

A few years ago, a model was proposed to predict the effect of the pore architecture of a bone graft substitute on its cell-mediated resorption rate. The aim of the present study was to compare the predictions of the model with the in vivo resorption rate of four β-tricalcium phosphate bone graft substitutes implanted in a sheep model. The simulation algorithm contained two main steps: (1) detection of the pores that could be accessed by blood vessels of 50μm in diameter, and (2) removal of one solid layer at the surface of these pores. This process was repeated until full resorption occurred. Since the pore architecture was complex, μCT data and fuzzy imaging techniques were combined to reconstruct the precise bone graft substitute geometry and then image processing algorithms were developed to perform the resorption simulation steps. The proposed algorithm was verified by comparing its results with the analytical results of a simple geometry and experimental in-vivo data of β-TCP bone substitutes with more complex geometry. An excellent correlation (r2>0.9 for all 4 bone graft substitutes) was found between simulation results and in-vivo data, suggesting that this resorption model could be used to (i) better understand the in vivo behavior of bone graft substitutes resorbed by cell-mediation, and (ii) optimize the pore architecture of a bone graft substitute, for example to maximize its resorption rate. © 2011 Elsevier Ltd. Source

Clauss M.,Clinic for Orthopedic and Trauma Surgery | Gersbach S.,Clinic for Orthopedic and Trauma Surgery | Butscher A.,RMS Foundation | Ilchmann T.,Clinic for Orthopedic and Trauma Surgery
Acta Orthopaedica

Background and purpose Even small differences in design variables for the femoral stem may influence the outcome of a hip arthroplasty. We performed a risk factor analysis for aseptic loosening of 4 different versions of cemented Müller-type straight stems with special emphasis on design modifications (2 shapes, MSS or SL, and 2 materials, CoNiCrMo (Co) or Ti-6Al-7Nb (Ti)). Methods We investigated 828 total hip replacements, which were followed prospectively in our in-house register. All stems were operated in the same setup, using Sulfix-6 bone cement and a second-generation cementing technique. Demographic and design-specific risk factors were analyzed using an adjusted Cox regression model. Results The 4 versions showed marked differences in 15-year stem survival with aseptic loosening as the endpoint: 94% (95% CI: 89-99) for MSS Co, 83% (CI: 75-91) for SL Co, 81% (CI: 76-87) for MSS Ti and 63% (CI: 56-71) for SL Ti. Cox regression analysis showed a relative risk (RR) for aseptic loosening of 3 (CI: 2-5) for stems made of Ti and of 2 (CI: 1-2) for the SL design. The RR for aseptic stem loosening increased to 8 (CI: 4-15) when comparing the most and the least successful designs (MSS Co and SL Ti). Interpretation Cemented Müller-type straight stems should be MSS-shaped and made of a material with high flexural strength (e.g. cobalt-chrome). The surface finish should be polished (Ra < 0.4 μm). These technical aspects combined with modern cementing techniques would improve the survival of Müller-type straight stems. This may be true for all types of cemented stems. © 2011 Nordic Orthopaedic Federation. Source

Bohner M.,RMS Foundation
Materials Today

An ageing population and the democratization of high-risk sports have led to a surge of bone-related diseases and bone fractures. As a result, the use of bone graft substitutes has dramatically increased in the last decade. A wide range of materials are considered, from metals to polymers, from injectable cements to complex porous solids. This article aims at presenting a concise, accessible overview of the field of resorbable bone graft substitute materials. A slight emphasis is set on synthetic materials, in particular calcium phosphates. © 2010 Elsevier Ltd. All rights reserved. Source

Bohner M.,RMS Foundation
European Cells and Materials

In the last 15 years, a large number of commercial ceramicbased cements and putties have been introduced as bone graft substitutes. As a result, large efforts have been made to improve our understanding of the specific properties of these materials, such as injectability, cohesion, setting time (for cements), and in vivo properties. The aim of this manuscript is to summarize our present knowledge in the field. Instead of just looking at scientific aspects, industrial needs are also considered, including mixing and delivery, sterilization, and shelf-life. Source

Bohner M.,RMS Foundation | Loosli Y.,RMS Foundation | Baroud G.,Universite de Sherbrooke | Lacroix D.,Institute for Bioengineering of Catalonia
Acta Biomaterialia

Hundreds of studies have been devoted to the search for the ideal architecture for bone scaffold. Despite these efforts, results are often contradictory, and rules derived from these studies are accordingly vague. In fact, there is enough evidence to postulate that ideal scaffold architecture does not exist. The aim of this document is to explain this statement and review new approaches to decipher the existing but complex link between scaffold architecture and in vivo response. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

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