Selina Poon1, Yen Hsun Chen2, Stephen F Wendolowski2, Adam Graver2, Ryan Nixon2, Terry Amaral2, Jon-Paul DiMauro2, Daniel M Walz3, Rachel C Gecelter2, Daniel A Grande4. 1. Department of Orthopaedics, Shriners for Children Medical Center, 909 South Fair Oaks Avenue, Pasadena, CA 91105, USA. Electronic address: spoon@shrinenet.org. 2. Department of Pediatric Orthopaedics, Cohen Children's Medical Center, 269-01 76th Avenue, New Hyde Park, NY 11040, USA. 3. Department of Radiology, Northwell Health, New Hyde Park, NY 11040, USA. 4. Orthopedic Research Laboratory, The Feinstein Institute for Medical Research, 350 Community Dr, Manhasset, NY 11030, USA.
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.
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 EOSpatients 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.
Authors: Hiroko Matsumoto; Rishi Sinha; Benjamin D Roye; Jacob R Ball; Kira F Skaggs; Jaysson T Brooks; Michelle C Welborn; John B Emans; Jason B Anari; Charles E Johnston; Behrooz A Akbarnia; Michael G Vitale; Robert F Murphy Journal: Spine Deform Date: 2022-07-03
Authors: Thomas D Alter; Derrick M Knapik; Martina Guidetti; Alejandro Espinoza; Jorge Chahla; Shane J Nho; Philip Malloy Journal: Orthop J Sports Med Date: 2022-05-06