title: Metal artifacts from titanium and steel screws in CT, 1.5T and 3T MR images of the tibial Pilon: a quantitative assessment in 3D.
abstract: Radiographs are commonly used to assess articular reduction of the distal tibia (pilon) fractures postoperatively, but may reveal malreductions inaccurately. While magnetic resonance imaging (MRI) and computed tomography (CT) are potential three-dimensional (3D) alternatives they generate metal-related artifacts. This study aims to quantify the artifact size from orthopaedic screws using CT, 1.5T and 3T MRI data. Three screws were inserted into one intact human cadaver ankle specimen proximal to and along the distal articular surface, then CT, 1.5T and 3T MRI scanned. Four types of screws were investigated: titanium alloy (TA), stainless steel (SS) (Ø =3.5 mm), cannulated TA (CTA) and cannulated SS (CSS) (Ø =4.0 mm, Ø empty core =2.6 mm). 3D artifact models were reconstructed using adaptive thresholding. The artifact size was measured by calculating the perpendicular distance from the central screw axis to the boundary of the artifact in four anatomical directions with respect to the distal tibia. The artifact sizes (in the order of TA, SS, CTA and CSS) from CT were 2.0, 2.6, 1.6 and 2.0 mm; from 1.5T MRI they were 3.7, 10.9, 2.9, and 9 mm; and 3T MRI they were 4.4, 15.3, 3.8, and 11.6 mm respectively. Therefore, CT can be used as long as the screws are at a safe distance of about 2 mm from the articular surface. MRI can be used if the screws are at least 3 mm away from the articular surface except for SS and CSS. Artifacts from steel screws were too large thus obstructed the pilon from being visualised in MRI. Significant differences (P<0.05) were found in the size of artifacts between all imaging modalities, screw types and material types, except 1.5T versus 3T MRI for the SS screws (P=0.063). CTA screws near the joint surface can improve postoperative assessment in CT and MRI. MRI presents a favourable non-ionising alternative when using titanium hardware. Since these factors may influence the quality of postoperative assessment, potential improvements in operative techniques should be considered.
authors.affiliation: 1 Institute of Health and Biomedical Innovation, Queensland University of Technology, QLD 4059, Australia ; 2 Centre of Advanced Imaging, University of Queensland, QLD 4072, Australia ; 3 Orthopaedics Department, Royal Brisbane and Women's Hospital, QLD 4006, Australia ; 4 Radiology Department, 5 Trauma Services, Princess Alexandra Hospital, QLD 4102, Australia.
authors.forename: Shairah
authors.initials: S
authors.lastname: Radzi
authors.affiliation: 1 Institute of Health and Biomedical Innovation, Queensland University of Technology, QLD 4059, Australia ; 2 Centre of Advanced Imaging, University of Queensland, QLD 4072, Australia ; 3 Orthopaedics Department, Royal Brisbane and Women's Hospital, QLD 4006, Australia ; 4 Radiology Department, 5 Trauma Services, Princess Alexandra Hospital, QLD 4102, Australia.
authors.forename: Gary
authors.initials: G
authors.lastname: Cowin
authors.affiliation: 1 Institute of Health and Biomedical Innovation, Queensland University of Technology, QLD 4059, Australia ; 2 Centre of Advanced Imaging, University of Queensland, QLD 4072, Australia ; 3 Orthopaedics Department, Royal Brisbane and Women's Hospital, QLD 4006, Australia ; 4 Radiology Department, 5 Trauma Services, Princess Alexandra Hospital, QLD 4102, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Robinson
authors.affiliation: 1 Institute of Health and Biomedical Innovation, Queensland University of Technology, QLD 4059, Australia ; 2 Centre of Advanced Imaging, University of Queensland, QLD 4072, Australia ; 3 Orthopaedics Department, Royal Brisbane and Women's Hospital, QLD 4006, Australia ; 4 Radiology Department, 5 Trauma Services, Princess Alexandra Hospital, QLD 4102, Australia.
authors.forename: Jit
authors.initials: J
authors.lastname: Pratap
authors.affiliation: 1 Institute of Health and Biomedical Innovation, Queensland University of Technology, QLD 4059, Australia ; 2 Centre of Advanced Imaging, University of Queensland, QLD 4072, Australia ; 3 Orthopaedics Department, Royal Brisbane and Women's Hospital, QLD 4006, Australia ; 4 Radiology Department, 5 Trauma Services, Princess Alexandra Hospital, QLD 4102, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Volp
authors.affiliation: 1 Institute of Health and Biomedical Innovation, Queensland University of Technology, QLD 4059, Australia ; 2 Centre of Advanced Imaging, University of Queensland, QLD 4072, Australia ; 3 Orthopaedics Department, Royal Brisbane and Women's Hospital, QLD 4006, Australia ; 4 Radiology Department, 5 Trauma Services, Princess Alexandra Hospital, QLD 4102, Australia.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Schuetz
authors.affiliation: 1 Institute of Health and Biomedical Innovation, Queensland University of Technology, QLD 4059, Australia ; 2 Centre of Advanced Imaging, University of Queensland, QLD 4072, Australia ; 3 Orthopaedics Department, Royal Brisbane and Women's Hospital, QLD 4006, Australia ; 4 Radiology Department, 5 Trauma Services, Princess Alexandra Hospital, QLD 4102, Australia.
authors.forename: Beat
authors.initials: B
authors.lastname: Schmutz
keywords: Computed tomography (CT); magnetic resonance imaging (MRI); metal artifacts; pilon; tibial plafond