An in vivo analysis of implanted programmable device interference during magnetically controlled growing rod lengthenings: a story of 129 lengthenings

Purpose Early-onset scoliosis (EOS) is often treated with magnetically controlled growing rods (MCGR) which can be lengthened with a magnetic external remote control (ERC). Many individuals with EOS have concomitant medical conditions which are managed with other implanted programmable devices (IPD). Some providers are concerned that the magnetic field generated during MCGR lengthening may interfere with other IPD, such as ventriculoperitoneal shunts (VPS), intrathecal baclofen pumps (ITBP), vagal nerve stimulators (VNS), and cochlear implants (CI). The aim of this study was to evaluate the safety of MCGR lengthenings in patients with EOS and other IPD. Methods This single-center, single-surgeon case series followed 12 patients with 13 IPD as they underwent treatment with MCGR. Post MCGR lengthening, monitoring of patient symptoms, and interrogation of IPD were conducted to evaluate for magnetic interference. Results After 129 MCGR lengthenings, post-lengthening VPS interrogation found 2 instances of potential interference in settings (both in Medtronic Strata shunts); however, no pre-lengthening interrogation was completed to confirm if these changes occurred prior to or during the lengthening procedure. ITBP interrogation found no changes, and there were no patient-reported adverse effects related to VNS or CI function. Conclusion It is safe and effective to utilize MCGR in patients with IPD. However, the possibility of magnetic interference must be considered, particularly in individuals with VPS. We recommend approaching with the ERC from a caudal direction to minimize potential interference and all patients be monitored during treatment. If possible, IPD settings should be assessed pre-lengthening, confirmed afterwards and readjusted if necessary. Level of evidence Level IV.