Safe Parameters for Utilizing Magnetic Growth Rods in Patient With a Vagal Nerve Stimulator and Case Report

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.

Does the presence of programmable implanted devices in patients with early onset scoliosis alter typical operative and postoperative practices? A survey of spine surgeons

PURPOSE

Operative and postoperative management of early onset scoliosis (EOS) patients with programmable implanted devices has not been well characterized in the literature. The aim of this study was to describe current practices for pediatric spine surgeons who operate on patients with these devices.

METHODS

An electronic survey was distributed to 167 pediatric spine surgeons between January and March of 2021. The survey queried participants on operative and postoperative management of patients with the following implanted devices: vagal nerve stimulators, ventriculoperitoneal shunts, intrathecal baclofen pumps, pacemakers, and cochlear implants. Descriptive statistics were used to assess survey data.

RESULTS

Fifty-three respondents (31.7% response rate) with a mean 16.5 (SD 12.0) years in practice completed the survey. Depending on the type of device present, surgeons report changing their operative plan anywhere from 28.6 to 60.1% of the time when inserting magnetically controlled growing rods. Most respondents reported performing transcranial motor evoked potentials (80.0-98.0%) and monopolar cautery (70.0-92.9%) across implanted devices. Only 10% (n = 5) of surgeons reported complications related to operative and/or postoperative management of these patients. No complications were related to cautery, neuromonitoring, or surgical placement of MCGRs.

CONCLUSIONS

This study demonstrates variation in operative and postoperative management of these patients with various programmable implanted devices. Much of this inconsistency in practice is likely due to decades old case reports, constantly changing device manufacturer recommendations, and/or published simulation studies. Reported heterogeneity in management across surgeons necessitates development of published guidelines regarding proper operative and postoperative management of patients with EOS and implanted devices.