The effect of metal artefact on the design of custom 3D printed acetabular implants
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RESEARCH
Open Access
The effect of metal artefact on the design of custom 3D printed acetabular implants Anna Di Laura1,2* , Johann Henckel1, Robert Wescott2, Harry Hothi1,2 and Alister J. Hart1,2
Abstract Background: 3D Printed custom-made implants constitute a viable option in patients with acetabular Paprosky III defects. In these patients, needing complex hip revision surgery, the appreciation of the bony defect is crucial to assure stable fixation of the customised implant, often intended to replace a failed one. We aimed to understand the effect of metal artefact on the design of customised implants. Methods: 26 patients with massive acetabular defects were referred, between May 2016 and September 2018, to our institution classified as “un-reconstructable” by other hospitals. They all received custom 3D-printed acetabular cups. A subset of them underwent two-stage revision surgery due to infection. We then extended the two-stage procedure to the cases where metal artefacts were significantly affecting the reading of the CT scans. CT scans of patients’ pelvises were taken pre and post-implant removal. We assessed for changes in bony shape and volume of the pelvis using 3D imaging software and quantified the effect on implant design with CAD software. Results: Eight (out of 26) patients (31%) underwent two-stage revision surgery. The CT bony reconstructions between the two timepoints changed in all cases. The changes were mostly associated to the shape and distribution of the acetabular defects. Three of these cases (37.5%) showed a remarkable difference in the remaining bone that led to a change in implant design. So far, there has been no difference in the clinical outcome between the patients who underwent single (n = 18) and two-stage surgery (n = 8). Conclusions: The shape of the acetabulum reconstructed from CT data is potentially altered by metal artefact and bone excised during removal of the failed component. For “end-of-road” acetabular reconstruction, we recommend surgeons consider the use of two-stage surgery to enable a reliable fitting of the complex shape of 3D-printed implants. Keywords: Paprosky acetabular classification, Revision hip surgery, Metal artefact, Computed tomography, Custom 3D printed implants
* Correspondence: [email protected] 1 The Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, London HA7 4LP, UK 2 Institute of Orthopaedics and Musculoskeletal Science, University College London, London, UK © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not
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