RMS Foundation

Bettlach, Switzerland

RMS Foundation

Bettlach, Switzerland
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Butscher A.,RMS Foundation | Butscher A.,ETH Zurich | Bohner M.,RMS Foundation | Hofmann S.,ETH Zurich | And 2 more authors.
Acta Biomaterialia | Year: 2011

This article reviews the current state of knowledge concerning the use of powder-based three-dimensional printing (3DP) for the synthesis of bone tissue engineering scaffolds. 3DP is a solid free-form fabrication (SFF) technique building up complex open porous 3D structures layer by layer (a bottom-up approach). In contrast to traditional fabrication techniques generally subtracting material step by step (a top-down approach), SFF approaches allow nearly unlimited designs and a large variety of materials to be used for scaffold engineering. Today's state of the art materials, as well as the mechanical and structural requirements for bone scaffolds, are summarized and discussed in relation to the technical feasibility of their use in 3DP. Advances in the field of 3DP are presented and compared with other SFF methods. Existing strategies on material and design control of scaffolds are reviewed. Finally, the possibilities and limiting factors are addressed and potential strategies to improve 3DP for scaffold engineering are proposed. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Bohner M.,RMS Foundation | Loosli Y.,RMS Foundation | Baroud G.,Université de Sherbrooke | Lacroix D.,Institute for Bioengineering of Catalonia
Acta Biomaterialia | Year: 2011

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.

Bashoor-Zadeh M.,Université de Sherbrooke | Baroud G.,Université de Sherbrooke | Bohner M.,RMS Foundation
Biomaterials | Year: 2011

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.

Doebelin N.,RMS Foundation | Doebelin N.,University of Bern | Kleeberg R.,TU Bergakademie Freiberg
Journal of Applied Crystallography | Year: 2015

Profex is a graphical user interface for the Rietveld refinement program BGMN. Its interface focuses on preserving BGMN's powerful and flexible scripting features by giving direct access to BGMN input files. Very efficient workflows for single or batch refinements are achieved by managing refinement control files and structure files, by providing dialogues and shortcuts for many operations, by performing operations in the background, and by providing import filters for CIF and XML crystal structure files. Refinement results can be easily exported for further processing. State-of-the-art graphical export of diffraction patterns to pixel and vector graphics formats allows the creation of publication-quality graphs with minimum effort. Profex reads and converts a variety of proprietary raw data formats and is thus largely instrument independent. Profex and BGMN are available under an open-source license for Windows, Linux and OS X operating systems.

An interlaboratory study (ILS, round robin) was conducted to assess the accuracy and precision of the phase quantification of calcium phosphate (CaP) bioceramics by X-ray diffraction (XRD) and Rietveld refinement. For that purpose, a mixture of hydroxyapatite and β-tricalcium phosphate, two CaP phases commonly used in synthetic bone graft substitutes, was prepared and sent to 12 laboratories for XRD analysis. Results from 26 different instruments were received and evaluated statistically according to ASTM E691-13. The statistical analysis revealed that the reproducibility standard deviation of phase quantities was approximately two times greater than the repeatability standard deviation, which is obtained by repeating the analysis on a single instrument configuration multiple times. The 95% reproducibility limit for phase quantities was R = ±1.67 wt%. The study also demonstrated that several participants overinterpreted their data in an attempt to refine crystallite sizes of the minor phase. © 2015 International Centre for Diffraction Data.

Bohner M.,RMS Foundation | Galea L.,RMS Foundation | Doebelin N.,RMS Foundation
Journal of the European Ceramic Society | Year: 2012

Despite 40 years of efforts, researchers have failed to provide calcium phosphate bone graft substitutes performing well enough to replace bone grafting procedures: their osteogenesis potential is limited, and calcium phosphates are too brittle. However, there is hope to solve the two afore-mentioned problems. First, it is now clear why nacre and bone are very tough despite a high ceramic load. Also, recent studies suggest that calcium and phosphate ions can trigger osteoinduction. The present article aims: (i) to review our current knowledge in the field of synthetic bone graft substitutes, (ii) to explain why ceramics and in particular calcium phosphates are still the most promising materials for bone graft substitution, and (iii) finally to describe the strategy to obtain osteoinductive calcium phosphate bone graft substitutes as strong as cortical bone. © 2012 Elsevier Ltd.

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 | Year: 2013

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.

Bohner M.,RMS Foundation
Materials Today | Year: 2010

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.

Bohner M.,RMS Foundation
European Cells and Materials | Year: 2010

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.

Habib M.,Université de Sherbrooke | Baroud G.,Université de Sherbrooke | Galea L.,RMS Foundation | Bohner M.,RMS Foundation
Acta Biomaterialia | Year: 2012

This study examined the use of ultrasonication to improve the injectability of an aqueous calcium phosphate paste. Ultrasonication was applied to the paste through the plunger of the delivery syringe. A factorial design of experiments with three investigated factors, liquid to powder ratio (LPR) (38%, 39% and 40%), the size of the delivery syringe (5 and 10 ml) and the amplitude of the 20 kHz power ultrasonication (0-30 μm), was used in this study. The volume fraction of the extruded paste was used to quantify injectability. Small injectability improvements were observed with an increase in LPR and decrease in syringe size, which is consistent with previously published results. The improvements due to ultrasonication were significant and remarkable. For example, when using the 5 ml syringe the injected volume fraction of the 38% LPR paste improved from 63.4 ± 2.3% without ultrasonication to 97.3 ± 2.4% with 30%. This result shows that ultrasonication is an effective solution to improve injectability. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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