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Outcomes of MCGR at > 3 year average follow-up in severe scoliosis: who undergoes elective revision vs UPROR?

Abstract

Purpose

The purpose of this study was to evaluate mid-term outcomes of magnetically controlled growing rods (MCGR), evaluate factors associated with unplanned return to the operating room (UPROR) vs achieving full length. Full length was defined as achieving > 85% of the elongating portion of the rod.

Methods

IRB approved retrospective single site study. 106 patients underwent MCGR between 2014 and 2020, 58 met inclusion criteria, all genders, ethnicities, and etiologies were included. Patients with < 1 year follow-up or previous instrumentation were excluded.

Results

Follow-up averaged 43 months. 23 patients achieved full length 13 were revised to a new MCGR and 10 to a fusion; 5 were fused due to skeletal maturity; 12 were still lengthening; 2 were being observed; 16 experienced UPROR. Major curves improved from 80° (50–114) preoperative to 40° (7–78) at most recent follow-up or prior to revision, and 24° (4–57) after fusion. Fusion patients averaged 1.3 (1–4) procedures prior to fusion and gained 75 mm (38–142) in T1–S1 length. 16 patients experienced UPROR, 11 were male (p = 0.0238). All failures to elongate were male as was the rod fracture. Age was not correlated with UPROR (p = 0.318), but did correlate with implant-specific causes of UPROR. Specifically, anchor failure was associated with younger age and rod failure with older age at implantation (p = 0.013). There was no correlation between UPROR and major curve, flexibility or kyphosis.

Conclusion

This is the largest site study evaluating mid-term outcomes in MCGR patients. At > 3.5 year follow-up 47% were electively revised, 27% underwent UPROR, 26% were still lengthening, and 3% were being observed. UPROR was associated with male gender and age at implantation was associated with implant-related causes of UPROR. MCGR continues to have high complication rates, better knowledge of MCGR outcomes may improve patient education, surgical timing, and decision-making.

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Funding

POSNA Research Startup Grant; Shriners Hospital for Children Directed Research Grant.

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Affiliations

Authors

Contributions

MCW: conception/design, data acquisition, analysis, interpretation, drafted/revised work, approved final version. DB: conception/design, interpretation, drafted/revised work, approved final version. All authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Corresponding author

Correspondence to Michelle Cameron Welborn.

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Conflict of interest

Dr. Welborn reports grants from POSNA, grants from Shriners Hospital for Children, during the conduct of the study; personal fees and other from Depuy Synthes, personal fees from Nuvasive, personal fees from Stryker/K2M, personal fees from and Zimmer/Biomet outside the submitted work. Dr. Bouton reports during the conduct of the study; personal fees from Medtronic outside the submitted work.

Ethical approval (IRB)

This is a Western IRB approved study. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (Western Copernicus Group (WCG)/Western Institutional Review Board (WIRB) on Feb 19, 2020 study number 1275477) and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all patients and their parents.

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Welborn, M.C., Bouton, D. Outcomes of MCGR at > 3 year average follow-up in severe scoliosis: who undergoes elective revision vs UPROR?. Spine Deform (2021). https://doi.org/10.1007/s43390-021-00424-1

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Keywords

  • MCGR
  • UPROR
  • Scoliosis
  • Complications
  • Outcomes