Abstract
ObjectivesThe implant constructs used in scoliosis surgery are often long with a high screw density. Therefore, it is generally believed that magnetic resonance imaging (MRI) should not be carried out after scoliosis surgery, with the result that computed tomography is often preferred despite the ionizing radiation involved. The objective of this study was to evaluate the MRI compatibility of long pedicle-screw-rod constructs at 1.5 T and 3 T using standardized methods of the American Society for Testing and Materials (ASTM).MethodsConstructs between 130 and 430 mm long were systematically examined according to the ASTM standards F2182 (radio frequency–induced heating), F2119 (susceptibility artifacts), F2213 (magnetically induced torque), and F2052 (magnetically induced displacement force).ResultsThe maximum heating in the magnetic field was 1.3 K. Heating was significantly influenced by magnetic field strength (p < 0.001), implant length (p = 0.048), and presence of cross-links (p = 0.001). The maximum artifact width for different lengths of the anatomically bent titanium rods with CoCr alloy ranged between 14.77 ± 2.93 mm (TSE) and 17.49 ± 1.82 mm (GRE) for 1.5 T and between 23.67 ± 2.39 mm (TSE) and 27.77 ± 2.37 mm (GRE) for 3 T. TiCP and TiAl showed the smallest and CoCr and CoCr Plus the largest artifact widths. The magnetically induced torque and displacement force were negligible.ConclusionsMRI following scoliosis surgery with long implant constructs is safe with the patient in supine position. Although susceptibility artifacts can severely limit the diagnostic value, the examination of other regions is possible.Key Points• Large spinal implants are not necessarily a contraindication for MRI; MR conditional status can be examined according to the ASTM standards F2182, F2119, F2213, and F2052.• A metallic pedicle-screw-rod system could be reliably and safely examined in all combinations of length (130 to 430 mm), configuration, and material in a B0at 1.5 T and 3 T.• According to ASTM F2503, the examined pedicle-screw-rod system is MR conditional and especially the young patients can benefit from a non-ionizing radiation MRI examination.
Highlights
The use of metallic implants such as pedicle screws and rods is currently standard in spinal surgery to treat deformity, degeneration, destruction, and trauma [1, 2]
The objective of this study was to evaluate the magnetic resonance imaging (MRI) safety and MR conditional status of a metallic pedicle-screw-rod system with different lengths (130 to 430 mm), configurations, and materials at magnetic field strengths of 1.5 T and 3 T based on standardized test methods of the ASTM
We found that even long implant constructs are MR conditional and safe in the standard clinical setting for MRI in patients with such implants with regard to RF-induced heating as well as magnetically induced torque and displacement force
Summary
The use of metallic implants such as pedicle screws and rods is currently standard in spinal surgery to treat deformity, degeneration, destruction, and trauma [1, 2]. The compatibility of various orthopedic implants with magnetic resonance imaging (MRI) has been studied [2,3,4], but the modern metallic pedicle-screw-rod systems have not been sufficiently investigated in this regard. A previously published study [1] on a pedicle-screw-rod system focused mainly on shorter implant constructs and used a field strength of 7 T. The pedicle screw density used here was lower and the 7-T magnetic field strength was higher than in routine clinical care because usually the patients are examined at 1.5 T and 3 T. Patients with long metallic pedicle-screw-rod constructs who need a tomographic examination, e.g., in the presence of postoperative complications or in scoliosis secondary to tumors such as neurofibromas, often undergo computed tomography (CT) despite the exposure to ionizing radiation. Due to the youth of many scoliosis patients, MRI would be preferable
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