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  • 1.
    Cronskär, Marie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Tinnsten, Mats
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Combined finite element and multibody musculoskeletal investigation of a fractured clavicle with reconstruction plate2015Ingår i: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 18, nr 7, s. 740-748Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper addresses the evaluation of clavicle fixation devices, by means of computational models. The aim was to develop

    a method for comparison of stress distribution in various fixation devices, to determine whether the use of multibody

    musculoskeletal input in such model is applicable and to report the approach. The focus was on realistic loading and the

    motivation for the work is that the treatment can be enhanced by a better understanding of the loading of the clavicle and

    fixation device. The method can be used to confirm the strength of customised plates, for optimisation of new plates and to

    complement experimental studies. A finite element (FE) mesh of the clavicle geometry was created from computed

    tomography data and imported into the FE solver where the model was subjected to muscle forces and other boundary

    conditions from a multibody musculoskeletal model performing a typical activity of daily life. A reconstruction plate and

    screws were also imported into the model. The combination models returned stresses and displacements of plausible

    magnitudes in all included parts and the result, upon further development and validation, may serve as a design guideline for

    improved clavicle fixation.

  • 2.
    Cronskär, Marie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    On customization of orthopedic implants - from design and additive manufacturing to implementation2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This doctoral thesis is devoted to studying the possibilities of using additive manufacturing (AM) and design based on computed tomography (CT), for the production of patient-specific implants within orthopedic surgery, initially in a broad perspective and, in the second part of the thesis focusing on customized clavicle osteosynthesis plates. The main AM method used in the studies is the Electron Beam Melting (EBM) technology. Using AM, the parts are built up directly from 3D computer models, by melting or in other ways joining thin layers of material, layer by layer, to build up the part. Over the last 20 years, this fundamentally new way of manufacturing and the rapid development of software for digital 3D reconstruction of anatomical models from medical imaging, have opened up entirely new opportunities for the design and manufacturing of patient-specific implants. Based on the information in a computed tomography (CT) scan, both digital and physical models of the anatomy can be created and of implants that are customized based on the anatomical models.

     

    The main method used is a number of case studies performed, focusing on different parts of the production chain, from CT-scan to final implant, and with several aims: learning about the details of the different steps in the procedure, finding suitable applications, developing the method and trying it out. The first study was on customized hip stems, focusing on the EBM method and its special preconditions and possibilities. It was followed by a study of bone plates, designed to follow the patient-specific bone contour, in this case a tibia fracture including the whole production chain. Further, four cases of patient-specific plates for clavicle fracture fixation were performed in order to develop and evaluate the method. The plates fit towards the patient’s bone were tested in cooperation with an orthopedic surgeon at Östersund hospital. In parallel with the case studies, a method for finite element (FE) analysis of fixation plates placed on a clavicle bone was developed and used for the comparative strength analysis of different plates and plating methods. The loading on the clavicle bone in the FE model was defined on a muscle and ligament level using multibody musculoskeletal simulation for more realistic loading than in earlier similar studies. 

     

    The initial studies (papers I and II) showed that the EBM method has great potential, both for the application of customized hip stems and bone plates; in certain conditions EBM manufacturing can contribute to significant cost reductions compared to conventional manufacturing methods due to material savings and savings in file preparation time. However, further work was needed in both of the application areas before implementation. The studies on the fracture fixation using patient-specific clavicle plates indicated that the method can facilitate the work for the surgeon both in the planning and in the operating room, with the potential of a smoother plate with a better fit and screw positioning tailored to the specific fracture (paper VI). However, a large clinical trial is required to investigate the clinical benefit of using patient-specific plates. The FE simulations showed similar stress distributions and displacements in the patient-specific plates and the commercial plates (papers III to VI).

     

    To summarize: the results of this thesis contribute to the area of digital design and AM in patient-specific implants with broad basis of knowledge regarding the technologies used and areas in which further work is needed for the implementation of the technology on a larger scale. Further, a method has been developed and initially evaluated for implementation in the area of clavicle fracture fixation, including an approach for comparing the strength of different clavicle plates.

  • 3.
    Cronskär, Marie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Strength analysis of clavicle fracture fixation devices and fixation techniques using finite element analysis with musculoskeletal force input2015Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 53, nr 8, s. 759-769Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the cases, when clavicle fractures are treated with a fixation plate,opinions are divided about the best position of the plate, type of plateand type of screw units. Results from biomechanical studies of claviclefixation devices are contradictory, probably partly because ofsimplified and varying load cases used in different studies. The anatomyof the shoulder region is complex, which makes it difficult andexpensive to perform realistic experimental tests; hence, reliablesimulation is an important complement to experimental tests. In thisstudy, a method for finite element simulations of stresses in theclavicle plate and bone is used, in which muscle and ligament force dataare imported from a multibody musculoskeletal model. The stressdistribution in two different commercial plates, superior and anteriorplating position and fixation including using a lag screw in thefracture gap or not, was compared. Looking at the clavicle fixation froma mechanical point of view, the results indicate that it is a majorbenefit to use a lag screw to fixate the fracture. The anterior platingposition resulted in lower stresses in the plate, and the anatomicallyshaped plate is more stress resistant and stable than a regularreconstruction plate.

  • 4.
    Cronskär, Marie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    The use of additive manufacturing in the custom design of orthopedic implants2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 5.
    Cronskär, Marie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Bäckström, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Modeling of fractured clavicles and reconstruction plates using CAD, finite element analysis and real musculoskeletal forces input2013Ingår i: WIT Transactions on Biomedicine and Health, WIT Press, 2013, s. 235-243Konferensbidrag (Refereegranskat)
    Abstract [en]

    This study focuses on the treatment options for clavicle fractures, more specifically the cases with a need for internal fixation: non-unions and some complex fractures. Enhancing the understanding of the loading of the bone and fixation device enables treatment options to be improved. The aim of the study was to develop a method for the realistic simulation of stresses and displacements in the bone and fixation device and to use this method to make comparisons between a conventional reconstruction plate and a customized plate, designed from patient-specific computed tomography (CT) data. In an earlier study, a finite element (FE) mesh of the clavicle geometry was created from CT data, subjected to muscle forces and other boundary conditions from a multibody musculoskeletal model and imported into the FE solver. In this study, a solid 3D model of the same clavicle geometry was created and the mesh was replaced by the solid model to make the FE-model more suitable for the comparison of different plates. An LCP Reco-Plate 3.5 straight, 6 holes (by Synthes) was compared with a customized plate which was designed to follow the anatomy of the bone. The LCP-Reco plate has tapered reconstruction segments throughout the plate to allow for the plate reshaping during surgery. The customized plate was designed without such segments and with a lower width than the LCP plate. The two different plates showed stresses and displacements of similar magnitudes. The customized plate had a more even stress distribution while the LCP plate had higher stress concentrations in the middle of the plate and on the edges of the tapered reconstruction segments. To the authors' best knowledge, this is the first FE model of a clavicle bone with plate and it may, upon further development, serve as a useful instrument for improved clavicle fixation.

  • 6.
    Cronskär, Marie
    et al.
    AIM Sweden.
    Legrell, Pererik
    Norrlands universitetssjukhus.
    Tidehag, Per
    Norrlands universitetssjukhus.
    Rännar, Lars-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Dental Implant Manufacturing using Electron Beam Melting – Geometry Deviation from Intraoral Scanning and from Cone Beam Computed Tomography2016Konferensbidrag (Övrigt vetenskapligt)
  • 7.
    Cronskär, Marie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    Rännar, Lars-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    Bäckström, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    Implementation of digital design and solid free-form fabrication for customization of implants in trauma orthopaedics2012Ingår i: Journal of medical and biological engineering, ISSN 1609-0985, Vol. 32, nr 2, s. 91-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bone plates for the fixation of complex fractures in proximity to joints often have to be reshaped to follow the bone contour. Good adhesion of the screws in areas where the bone is osteoporotic is also a challenge. One possible solution to these issues is to tailor-make plates by creating a digital three-dimensional model of the fracture from a computed tomography (CT) scan, digitally reducing the fracture, designing a plate, and finally manufacturing it directly from the digital model with solid free-form fabrication (SFF) technology. This study designs a custom plate for a distal tibia fracture, and investigates and refines the procedure from the CT scan to the final implant, with the aim of making it usable in trauma orthopaedics. The bone plate is manufactured using electron beam melting (EBM) technology. The challenges of bone plate design using digitalization and SFF are discussed. The virtual models created by the engineer while digitally reducing the fracture and modeling the plate are valuable for the physician while planning the surgery. A combination of surgery planning and digital plate design improves the surgeon's preparations and ensures correspondence between the plan and the designed implant. The proposed procedure, with the approximate required time in brackets, includes the separation of bone in the DICOM file (60 min), the reduction of fracture (5-30 min), revision (30 min), modelling of the plate (30-120 min), confirmation (30 min), manufacturing with SFF (10 h), post-processing (60 min), and finally cleaning and sterilization (90 min). The whole procedure requires about three working days.

  • 8.
    Cronskär, Marie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Rännar, Lars-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Bäckström, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Production of Customized Hip Stem Prostheses: a Comparison Between Machining and Additive Manufacturing2013Ingår i: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 19, nr 5, s. 365-372Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose - The purpose of this paper is to study the use of the additive manufacturing (AM) method, electron beam melting (EBM), for manufacturing of customized hip stems. The aim is to investigate EBM's feasibility and commercial potential in comparison with conventional machining, and to map out advantages and drawbacks of using EBM in this application. One part of the study concerns the influence on the fatigue properties of the material, when using the raw surface directly from the EBM machine, in parts of the implant.Design/methodology/approach - The research is based on a case study of manufacturing a batch of seven individually adapted hip stems. The stems were manufactured both with conventional machining and with EBM technology and the methods were compared according to the costs of materials, time for file preparation and manufacturing. In order to enhance bone ingrowths in the medial part of the stem, the raw surface from EBM manufacturing is used in that area and initial fatigue studies were performed, to get indications on how this surface influences the fatigue properties.Findings - The cost reduction due to using EBM in this study was 35 per cent. Fatigue tests comparing milled test bars with raw surfaced bars indicate a reduction of the fatigue limit by using the coarse surface.Originality/value - The paper presents a detailed comparison of EBM and conventional machining, not seen in earlier research. The fatigue tests of raw EBM-surfaces are interesting since the raw surface has shown to enhance bone ingrowths and therefore is suitable to use in some medical applications.

  • 9.
    Cronskär, Marie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    Rännar, Lars-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    Bäckström, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    Koptioug, Andrei
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    Application of electron beam melting to titanium hip stem Implants2008Ingår i: / [ed] Katalinic, B., Vienna: DAAAM International Vienna , 2008, s. 1559-1560Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Free Form Fabrication Process (FFF) is nowadays an accepted technology widely used for prototyping and manufacturing. However, it is still in an expansive phase and new applications like direct manufacturing of implants are evolving continuously. Present work describes the possibilities provided by the electron beam melting (EBM) method for orthopedics; in particular hip stem implant manufacturing. The conventional machining used for individually adapted prostheses typically involves advanced milling with the drawback of removing up to 80% of the material. This paper addresses the economic feasibility of using an additive approach for the manufacturing of typical orthopedic implants. The studied implants were manufactured from biocompatible Ti-6Al-4V alloy using both EBM and conventional CNC technologies and compared according to material consumption, manufacturing time and cost.

  • 10.
    Cronskär, Marie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Rännar, Lars-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Bäckström, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Nilsson, K-G
    Samuelsson, B
    Patient-specific bone plates for clavicle fractures: Design, manufacturing and strength analysisManuskript (preprint) (Övrigt vetenskapligt)
  • 11.
    Cronskär, Marie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Rännar, Lars-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Bäckström, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Nilsson, Kjell G.
    Umea Univ, Dept Surg & Perioperat Sci Orthopaed, S-90187 Umea, Sweden.
    Samuelsson, Börje
    Ostersunds Sjukhus, Dept Orthopaed, Ortopedmottagningen, S-83183 Ostersund, Sweden.
    Patient-Specific Clavicle Reconstruction Using Digital Design and Additive Manufacturing2015Ingår i: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001, Vol. 137, nr 11, artikel-id 111418Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is a trend toward operative treatment for certain types of clavicle fractures and these are usually treated with plate osteosynthesis. The subcutaneous location of the clavicle makes the plate fit important, but the clavicle has a complex shape, which varies greatly between individuals and hence standard plates often have a poor fit. Using computed tomography (CT) based design, the plate contour and screw positioning can be optimized to the actual case. A method for patient-specific plating using design based on CT-data, additive manufacturing (AM), and postprocessing was initially evaluated through three case studies, and the plate fit on the reduced fracture was tested during surgery (then replaced by commercial plates). In all three cases, the plates had an adequate fit on the reduced fracture. The time span from CT scan of the fracture to final implant was two days. An approach to achieve functional design and screw-hole positioning was initiated. These initial trials of patient-specific clavicle plating using AM indicate the potential for a smoother plate with optimized screw positioning. Further, the approach facilitates the surgeon's work and operating time can be saved.

  • 12.
    Koptyug, Andrey
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Rännar, Lars-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Bäckström, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Cronskär, Marie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Additive Manufacturing for Medical and Biomedical Applications: Advances and Challenges2014Ingår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, s. 1286-1291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Additive Manufacturing (AM) has solidly established itself not only in rapid prototyping but also in industrial manufacturing. Its success is mainly determined by a possibility of manufacturing components with extremely complex shapes with minimal material waste. Rapid development of AM technologies includes processes using unique new materials, which in some cases is very hard or impossible to process any other way. Along with traditional industrial applications AM methods are becoming quite successful in biomedical applications, in particular in implant and special tools manufacturing. Here the capacity of AM technologies in producing components with complex geometric shapes is often brought to extreme.

    Certain issues today are preventing the AM methods taking its deserved place in medical and biomedical applications. Present work reports on the advances in further developing of AM technology, as well as in related post-processing, necessary to address the challenges presented by biomedical applications. Particular examples used are from Electron Beam Melting (EBM), one of the methods from the AM family.

1 - 12 av 12
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