12th Conference on Industrial Computed Tomography, Fürth, Germany (iCT 2023), www.ict2023.org Copyright 2022 - by the Authors. Licensed under a Creative Commons Attribution 4.0 International License. Non-destructvive evaluation of patient-specific, additively manufactured titanium foot implants using microcomputed tomography Martin Holzleitner 1 , Michael Happl 2 , Reinhard Hubmann 2 , Norica Godja 3 , Johann Kastner 1 , Klemens Trieb 4 , Sascha Senck 1 1 University of Applied Sciences Upper Austria, Stelzhamerstraße 23, 4600 Wels, Austria 2 FOTEC Forschungs- und Technologietransfer GmbH, Viktor-Kaplan-Strasse 2, 2700 Wiener Neustadt, Austria 3 CEST Kompetenzzentrum für elektrochemische Oberflächentechnologie GmbH, Viktor-Kaplan-Straße 2, 2700 Wiener Neustadt, Austria 4 Department of Orthopedic and Trauma Surgery, Paracelsus Medical University Salzburg, Müllner Hauptstraße 48, 5020 Salzburg, Austria Keywords: Titanium alloy, Selective Laser Melting, Microcomputed Tomography, Nominal-Actual Comparison, Topology 1 Introduction In all fractures occurring in the foot the most common fracture area is the forefoot with an occurrence rate of 87%. [1]. As the first metatarsal (MT1) bears approximately one third of a persons body weight [2] and because of its relative size, strength, and mobility compared to the lesser metatarsals, it is less frequently subject to injury in healthy humans [3]. However, because of its bodyweight bearing role, the tolerance of any displacement or angulation of the MT1 is very poor. If a displaced or angulated fracture occurs in any portion of the MT1, an anatomic reduction is required, most importantly in order to eliminate the disturbance of the weight-bearing balance in the forefoot [2]. In highly displaced or angulated fractures, an anatomic reduction in form of internal fixation by surgery is necessary in order to maintain the weight-bearing properties of the forefoot [4]. High rigidity in the fixation of the MT1 is important to promote the bone healing process. Therefore a system consisting of implant plates with a uniform, relatively straight shape and screws is often chosen as the form of treatment [5]. These plates have to be adapted to the shape of the bone during surgery by the means of plastic deformation which may cause changes to the mechanical properties of the implant [6]. It is therefore beneficial to create an implant design that is personalized to the individual bone geometry. Additive manufacturing (AM) is a rapid prototyping processes that builds up three-dimensional models by progressively adding thin layers of a material based on the data of a digital model. Using AM, elements with complex shapes can be constructed via computer aided design (CAD) and layer-wise manufacturing. During AM processes, feedstock materials like powder, wires or sheets are consolidated into a dense metallic part by melting and solidification of the feedstock material. Layer-by-layer melting is achieved with different forms of energy source such as laser or electron beam [7]. Titanium alloys are often used in biomedical applications and can be used as feedstock materials for Selective Laser Melting (SLM). Since the quality of a part SLM highly depends on the process parameters [8], internal defects like pores or geometric inaccuracy due to thermal deformation can lead to final products that have to be rejected. In this contribution we are using X-ray microcomputed tomography (XCT) to non- destructively evaluate personalized metaltarsal implants adapted to individual bone shape in order to detect potential internal defects and warpage. In addition, we extract the outer surface of each part for nominal-actual comparisons of as-built and surface- treated (e.g. using Electropolishing) of selected implants. Using this approach, the internal as well as external geometry of the final implant are be evaluated, i.e. in relation to pores that negatively influence fatigue life and warpage that influences the patient-specific fit of the implant. 2 Materials and methods The geometry of fixation plates for diaphyseal fractures of the metatarsal bones is governed by the form of the bone and the implants´ function, e.g. stabilizing a fracture zone. We chose a common design characterized by normal and slotted holes for the basic shape of the planar implant plate. The geometry of the first metatarsal bone (MT1) was extracted from an existing finite element model (FE-model) of an entire human foot based on medical computed tomograpgy (CT) data (Holzleitner, 2021). This model was created by segmenting each bone individually and generating the final finite element mesh utilizing an adaptive meshing algorithm provided by the visualization software AVIZO 3D. After extracting the MT1 as stereolithography file (STL), it was imported into the CAD software Fusion 360 and subsequently converted into a solid, homogeneous body. An artificial fracture in the center of the diaphysis was added to the model by using a cutting plane angulated dorsally by 30 degrees related to an axis running from the center of the proximal head of the MT1 to the center of the distal head. In the following step, two holes, one in the proximal and one in the distal bone half respectively were added to the MT1 model resembling the holes for More info about this article: https://www.ndt.net/?id=27731 https://doi.org/10.58286/27731