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Cadaveric Study of the Safety and Device Functionality of Magnetically Controlled Growing Rods After Exposure to Magnetic Resonance Imaging

  • Early Onset Scoliosis
  • Published:
Spine Deformity Aims and scope Submit manuscript

Abstract

Study Design

Cadaveric study.

Objective

To establish the safety and efficacy of magnetically controlled growing rods (MCGRs) after magnetic resonance imaging (MRI) exposure.

Summary of Background Data

MCGRs are new and promising devices for the treatment of early-onset scoliosis (EOS). A significant percentage of EOS patients have concurrent spinal abnormalities that need to be monitored with MRI. There are major concerns of the MRI compatibility of MCGRs because of the reliance of the lengthening mechanism on strongly ferromagnetic actuators.

Methods

Six fresh-frozen adult cadaveric torsos were used. After thawing, MRI was performed four times each: baseline, after implantation of T2–T3 thoracic rib hooks and L5–S1 pedicle screws, and twice after MCGR implantation. Dual MCGRs were implanted in varying configurations and connected at each end with cross connectors, creating a closed circuit to maximize MRI-induced heating. Temperature measurements and tissue biopsies were obtained to evaluate thermal injury. MCGRs were tested for changes to structural integrity and functionality. MRI images obtained before and after MCGR implantation were evaluated.

Results

Average temperatures increased incrementally by 1.1°C, 1.3°C, and 0.5°C after each subsequent scan, consistent with control site temperature increases of 1.1°C, 0.8°C, and 0.4°C. Greatest cumulative temperature change of +3.6°C was observed adjacent to the right-sided actuator, which is below the 6°C threshold cited in literature for clinically detectable thermal injury. Histologic analysis revealed no signs of heat-induced injury. All MCGR actuators continued to function properly according to the manufacturer’s specifications and maintained structural integrity. Significant imaging artifacts were observed, with the greatest amount when dual MCGRs were implanted in standard/offset configuration.

Conclusions

We demonstrate minimal MRI-induced temperature change, no observable thermal tissue injury, preservation of MCGR-lengthening functionality, and no structural damage to MCGRs after multiple MRI scans. Expectedly, the ferromagnetic actuators produced substantial MR imaging artifacts.

Level of Evidence

Level V.

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Author information

Authors and Affiliations

  1. Department of Orthopaedics, Shriners for Children Medical Center, 909 South Fair Oaks Avenue, 91105, Pasadena, CA, USA

    Selina Poon MD

  2. Department of Pediatric Orthopaedics, Cohen Children’s Medical Center, 269-01 76th Avenue, 11040, New Hyde Park, NY, USA

    Yen Hsun Chen MD, Stephen F. Wendolowski BS, Adam Graver MD, Ryan Nixon MD, Terry Amaral MD, Jon-Paul DiMauro MD & Rachel C. Gecelter BS

  3. Department of Radiology, Northwell Health, 11040, New Hyde Park, NY, USA

    Daniel M. Walz MD

  4. Orthopedic Research Laboratory, The Feinstein Institute for Medical Research, 350 Community Dr, 11030, Manhasset, NY, USA

    Daniel A. Grande PhD

Authors
  1. Selina Poon MD
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  2. Yen Hsun Chen MD
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  3. Stephen F. Wendolowski BS
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  4. Adam Graver MD
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  5. Ryan Nixon MD
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  6. Terry Amaral MD
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  7. Jon-Paul DiMauro MD
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  8. Daniel M. Walz MD
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  9. Rachel C. Gecelter BS
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  10. Daniel A. Grande PhD
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Corresponding author

Correspondence to Selina Poon MD.

Additional information

Author disclosures: SP (grants from Ellipse Technologies, NuVasive, and the Scoliosis Research Society, during the conduct of the study; other from NuVasive, outside the submitted work); YHC (grants from Ellipse Technologies, NuVasive, and Scoliosis Research Society, during the conduct of the study); SFW (grants from Ellipse Technologies, NuVasive, and the Scoliosis Research Society, during the conduct of the study); AG (grants from Ellipse Technologies, NuVasive, and the Scoliosis Research Society, during the conduct of the study); RN (grants from Ellipse Technologies, NuVasive, and the Scoliosis Research Society, during the conduct of the study); TA (grants from Ellipse Technologies, NuVasive, and the Scoliosis Research Society, during the conduct of the study); Jon-PD (grants from Ellipse Technologies, NuVasive, and the Scoliosis Research Society, during the conduct of the study); DMW (grants from Ellipse Technologies, NuVasive, and the Scoliosis Research Society, during the conduct of the study); RCG (grants from Ellipse Technologies, grants from NuVasive, grants from Scoliosis Research Society, during the conduct of the study); DAG (grants from Ellipse Technologies, NuVasive, and the Scoliosis Research Society, during the conduct of the study).

This research was supported by Ellipse Technologies, NuVasive, and Scoliosis Research Society Grants. We gratefully acknowledge the contributions of the Northwell Health Bioskills Education Center for their facilities and support staff, and Meredith Akerman for her statistical support.

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Poon, S., Chen, Y.H., Wendolowski, S.F. et al. Cadaveric Study of the Safety and Device Functionality of Magnetically Controlled Growing Rods After Exposure to Magnetic Resonance Imaging. Spine Deform 6, 290–298 (2018). https://doi.org/10.1016/j.jspd.2017.11.003

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  • DOI: https://doi.org/10.1016/j.jspd.2017.11.003

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