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Production of Customized Hip Stem Prostheses: a Comparison Between Machining and Additive Manufacturing
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.ORCID iD: 0000-0001-5954-5898
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
2013 (English)In: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 19, no 5, 365-372 p.Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
2013. Vol. 19, no 5, 365-372 p.
Keyword [en]
Orthopedic implants, hip stem, electron beam melting, additive layer manufacturing
National Category
Medical Materials
Identifiers
URN: urn:nbn:se:miun:diva-14391DOI: 10.1108/RPJ-07-2011-0067ISI: 000323021700008Scopus ID: 2-s2.0-84881395614OAI: oai:DiVA.org:miun-14391DiVA: diva2:436653
Available from: 2011-08-24 Created: 2011-08-24 Last updated: 2016-09-21Bibliographically approved
In thesis
1. The use of additive manufacturing in the custom design of orthopedic implants
Open this publication in new window or tab >>The use of additive manufacturing in the custom design of orthopedic implants
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2011. 14 p.
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 63
Keyword
additive manufacturing (AM), electron beam melting (EBM), total hip replacement (THR), orthopedic imiplants, digital design, computer aided design (CAD), bone plates
Identifiers
urn:nbn:se:miun:diva-14390 (URN)978-91-86694-42-5 (ISBN)
Presentation
2011-05-27, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2011-08-24 Created: 2011-08-24 Last updated: 2012-08-01Bibliographically approved
2. On customization of orthopedic implants - from design and additive manufacturing to implementation
Open this publication in new window or tab >>On customization of orthopedic implants - from design and additive manufacturing to implementation
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Sundsvall, Sweden: Kopieringen, Mid Sweden University, 2014. 60 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 191
Keyword
Patient-specific implants, Additive manufacturing, Electron beam melting, Multibody musculoskeletal analysis, Orthopedic implants, Clavicle, Finite element analysis, Computer aided design, Osteosynthesis plate, Hip stem implants
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:miun:diva-22902 (URN)978-91-87557-63-7 (ISBN)
Supervisors
Available from: 2014-09-15 Created: 2014-09-11 Last updated: 2015-03-13Bibliographically approved

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