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Evaluation of the translational and rotational forces acting on a highly ferromagnetic orthopedic spinal implant in magnetic resonance imaging
Author(s) -
McComb Christie,
Allan David,
Condon Barrie
Publication year - 2009
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.21668
Subject(s) - implant , orthopedic surgery , torque , magnetic resonance imaging , fixation (population genetics) , deflection (physics) , rotation (mathematics) , materials science , orthodontics , biomedical engineering , medicine , physics , surgery , computer science , radiology , optics , population , environmental health , thermodynamics , artificial intelligence
Purpose To assess the translational and rotational forces acting on a highly ferromagnetic orthopedic spinal implant in 1.5T and 3.0T magnetic resonance (MR) systems. Materials and Methods The translational forces and rotational forces, or torques, acting on the implant were measured using existing methods and assessed using the guidelines produced by the American Society for Testing and Materials (ASTM). Results The measured translational forces were many times greater than for any other orthopedic implant previously recorded in the literature and, based on deflection angle criteria, would be considered unsafe in both MR systems. However, due to the rigid fixation of orthopedic implants in bone, implant migration is considered highly unlikely. Several constituent components of the implant were subjected to large torques, in some cases an order of magnitude greater than the corresponding torque due to gravity. However, the counterbalancing effect of the configuration of the combined implant results in a net torque that is less than the torque due to gravity. Conclusion The translational and rotational forces acting on the implant in both 1.5T and 3.0T MR systems are substantial, but based on theoretical considerations are unlikely to result in implant migration or rotation. J. Magn. Reson. Imaging 2009;29:449–453. © 2009 Wiley‐Liss, Inc.