Safety and compatibility of magnetic-controlled growing rods and magnetic resonance imaging

Abstract

Disclosures: Ellipse Technologies donated the 2 magnetically controlled growing rods that were used in this study.OMS has previously received travel grants from Ellipse Technologies to support attendance at academic spinal meetings. OMS has previously received an honorarium from Ellipse Technologies for preparing and delivering a symposium at an academic spinal meeting. None of these disclosures relates to this study.The authors have no other financial or competing interests to disclose in relation to this work. Purpose:Magnetically controlled growth rods (MCGRs) are a new technology for the management of early-onset paediatric deformity enabling guided spinal growth by controlling the curvature. These rods contain a rare-earth magnet and are contraindicated for MRI. We have investigated the behavior MCGRs to determine whether MRI adversely affects rod properties and to determine the extent of image distortion. Methods:This is an in-vitro experiment using two magnetic growth rods secured in a 1.5 T MRI. A gradient echo sequence MRI was performed to evaluate whether the rods elongated, contracted or rotated during scanning and a phantom model was used to evaluate the amount of artifact induced.Results:The rod was not activated or subsequently impaired by the process of MRI. Image distortion of 28.9 cm was seen with the phantom model measured from the magnet housing. Conclusions:This study has demonstrated that there are no detrimental effects of MRI on the MCGR and imaging of the head and neck phantom can still be interpreted. Further in-vivo study is warranted.

Current status of the magnetically controlled growing rod in treatment of early-onset scoliosis: What we know after a decade of experience

“…The MCGR is not advised if patients require magnetic resonance imaging (MRI) to assess a pathology such as syringomyelia. Although no adverse effects have been shown with using the MRI, 38,39 image artifacts of up to 30 cm of image distortion have been observed. Hence, the spinal cord lesion cannot be monitored adequately.…”

Early-Onset Spinal Deformity in Neurofibromatosis Type 1

“…MCGRs may reduce the ability to detect spinal tumors on MRI. Although MRI is the “gold standard” for diagnosing and monitoring neurofibromas with rapid growth rates, MCGRs contain magnets and ferromagnetic materials that produce major scatter and image distortion in the areas within 20 cm of the actuator 32-34 . Scatter from MCGRs reduces resolution and impairs visualization in critical areas of the trunk, reducing the ability to monitor neurofibroma growth using MRI and to assess the potential for MPNST.…”

Growing spine deformities: Are magnetic rods the final answer?

“…Budd et al[23] presenting their experimental study stated the safety of MRI with the MAGEC rods in-situ , i.e ., the lengthening mechanism was not triggered. They found no reduction or enhancement in the ability of the rods to lengthen but the rods did produce an artifact in imaging the spine.…”