Abstract
Introduction
The advent of MRI-compatible external fixation devices has made the use of MRI possible in patients who have been treated with external fixation. However, although there have been multiple studies determining the safety of MRI scans with external fixator devices, there are no studies determining the artifact effect these devices can have on the MRI image. The purpose of our study was to evaluate the effect of two popular brands (Stryker and Synthes) of MRI-compatible external fixators on the diagnostic capacity of a knee MRI. We hypothesize that (1) MRI images would have higher noise due to the presence of an external fixator and (2) images of high diagnostic capacity will be obtainable in the presence of each external fixator spanning the knee.
Methods
Using seven cadaveric knees, a study was performed to analyze MRI images taken in the presence each external fixator. Scans taken with no external fixator present served as controls. Signal-to-noise ratios (SNRs) were measured at five anatomic structures. These structures were compared as a quantitative measure of image quality. A qualitative analysis was also performed using a five-point grading scale to assess the influence of metal artifact on the quality of the images. Each scan was graded by three blinded musculoskeletal radiologists focusing on six key anatomic structures.
Results
A reduction in SNR was identified on the external fixator group compare to the control groups at the patella tendon, MM and PCL. Qualitative scoring by three expert radiologists showed no difference in ability to identify the six key anatomic landmarks between the Stryker, Synthes and control images.
Conclusion
Although the presence of external fixation devices does increase the noise artifact in MRI scans, patients treated with these external fixators can undergo MRI of local structures with high likelihood of obtaining diagnostic quality images.
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References
Fischer SP, Fox JM, Del Pizzo W, Friedman MJ, Snyder SJ, Ferkel RD (1991) Accuracy of diagnoses from magnetic resonance imaging of the knee. A multi-center analysis of one thousand and fourteen patients. J Bone Joint Surg Am 73:2–10
Bucholz RW, Heckman JD, Court-Brown CM (2006) Rockwood & Green’s fractures in adults. Lippincott Williams and Wilkins, Philadelphia
Chen FS, Rokito AS, Pitman MI (2000) Acute and chronic posterolateral rotatory instability of the knee. J Am Acad Orthop Surg 8:97–110
Kumar R, Lerski RA, Gandy S, Clift BA, Abboud RJ (2006) Safety of orthopedic implants in magnetic resonance imaging: an experimental verification. J Orthop Res 24:1799–1802. doi:10.1002/jor.20213
Shellock FG (1996) MR imaging and cervical fixation devices: evaluation of ferromagnetism, heating, and artifacts at 1.5 Tesla. Magn Reson Imaging 14:1093–1098
Shellock FG, Morisoli S, Kanal E (1993) MR procedures and biomedical implants, materials, and devices: 1993 update. Radiology 189:587–599. doi:10.1148/radiology.189.2.8210394
Cannada LK, Herzenberg JE, Hughes PM, Belkoff S (1995) Safety and image artifact of external fixators and magnetic resonance imaging. Clin Orthop Relat Res 317:206–214
Davison BL, Cantu RV, Van Woerkom S (2004) The magnetic attraction of lower extremity external fixators in an MRI suite. J Orthop Trauma 18:24–27
Luechinger R, Boesiger P, Disegi JA (2007) Safety evaluation of large external fixation clamps and frames in a magnetic resonance environment. J Biomed Mater Res B Appl Biomater 82:17–22. doi:10.1002/jbm.b.30699
Nyenhuis J (2005) Magnetic resonance imaging testing of external fixation frames: Stryker Hoffmann II MRI vs. Synthes MRI safe. Stryker, Mahwah
Henkelman RM (1985) Measurement of signal intensities in the presence of noise in MR images. Med Phys 12:232–233
De Wilde J, Price D, Curran J, Williams J, Kitney R (2002) Standardization of performance evaluation in MRI: 13 years’ experience of intersystem comparison. Concepts in Magn Reson 15:111–116
Kuhl CK, Textor J, Gieseke J, von Falkenhausen M, Gernert S, Urbach H, Schild HH (2005) Acute and subacute ischemic stroke at high-field-strength (3.0-T) diffusion-weighted MR imaging: intraindividual comparative study. Radiology 234:509–516. doi:10.1148/radiol.2342031323
Kuhl CK, Gieseke J, von Falkenhausen M, Textor J, Gernert S, Sonntag C, Schild HH (2005) Sensitivity encoding for diffusion-weighted MR imaging at 3.0 T: intraindividual comparative study. Radiology 234:517–526. doi:10.1148/radiol.2342031626
Harris CA, White LM (2006) Metal artifact reduction in musculoskeletal magnetic resonance imaging. Orthop Clin N Am 37:349–359, vi. doi:10.1016/j.ocl.2006.04.001
Sofka CM, Potter HG, Adler RS, Pavlov H (2006) Musculoskeletal imaging update: current applications of advanced imaging techniques to evaluate the early and long-term complications of patients with orthopedic implants. HSS J 2:73–77. doi:10.1007/s11420-005-0131-1
White LM, Buckwalter KA (2002) Technical considerations: CT and MR imaging in the postoperative orthopedic patient. Semin Musculoskelet Radiol 6:5–17. doi:10.1055/s-2002-23160
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Elsissy, P., Akpolat, Y.T., Chien, A. et al. MRI evaluation of the knee with non-ferromagnetic external fixators: cadaveric knee model. Eur J Orthop Surg Traumatol 25, 933–939 (2015). https://doi.org/10.1007/s00590-015-1655-9
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DOI: https://doi.org/10.1007/s00590-015-1655-9