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Outcomes of Primary and Conversion Magnetically Controlled Growth Rods Are Different at Two-Year Follow-up: Results of North American Release

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Abstract

Study design

Multicenter retrospective review.

Objectives

To compare the radiographic outcomes and complication rates in patients with primary and conversion magnetically controlled growing rod (MCGR) implants at one and two years after surgery.

Summary of background data

Many initial early-onset scoliosis (MCGR) implantations in the United States were conversions from other types of growth-friendly systems, and the outcome similarities and differences between primary and conversion MCGR implantation procedures are still relatively unknown.

Methods

Multicenter retrospective review of EOS patients from two multicenter EOS registries identified consecutive EOS patients treated from 2014 to 2017 with a minimum of one-year follow-up. In addition, a subset of these patients who had two-year follow-up were further analyzed.

Results

In total, 383 MCGR patients were identified, of which 272 (71%) were primary (P) and 111 (29%) were conversion (C). Group P patients had significantly greater coronal curves at the time of MCGR implantation and greater initial coronal correction. There was no statistically significant difference in Cobb correction at one year or between follow-up at one and two years. The preimplantation thoracic spine height was identical in both groups, with statistically greater improvement at initial implantation in P than in C patients. Significantly greater height gains were seen in P than in C patients in the one-year follow-up cohort. There was a higher rate of complications in the C group than in the P group; however, the difference was not statistically significant. Overall, most complications were implant-related. No loss of curve correction occurred in either group.

Conclusions

Patients with primary MCGR insertion can be expected to have greater radiographic correction and spine length gain than those with conversion from growth-friendly instrumentation to MCGR, most likely because of increased spine stiffness in conversion patients. The rate of complications, primarily implant-related, remains higher in conversion than in primary insertion patients.

Level of Evidence

Level III.

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Authors and Affiliations

  1. Division of Pediatric Orthopedics, Columbia University Medical Center, 630 West 168th Street, 10032, New York, NY, USA

    Chun Wai Hung MEng, Michael G. Vitale MD, MPH & Hiroko Matsumoto PhD

  2. Shriners Hospital for Children, 3551 N Broad St, 19140, Philadelphia, PA, USA

    Amer Samdani MD

  3. Department of Orthopaedics, University of Utah, 201 Presidents Cir, 84112, Salt Lake City, UT, USA

    John T. Smith MD

  4. Cincinnati Children’s Hospital, 3333 Burnet Avenue, 45229-3026, Cincinnati, OH, USA

    Peter F. Sturm MD, MBA

  5. Johns Hopkins Hospital, 1800 Orleans St, 21287, Baltimore, MD, USA

    Paul D. Sponseller MD, MBA

  6. Shriners Hospital for Children, 4400 Clayton Ave, 63110, St. Louis, MO, USA

    Scott J. Luhmann MD

  7. Children’s Spine Foundation, P. O. Box 397, 19481, Valley Forge, PA, USA

    Tricia Hilaire MPH

  8. Dalhousie University, B3H 4R2, Halifax, Nova Scotia, Canada

    Ron El-Hawary MD, MSc

  9. Department of Orthopaedic Surgery, University of Tennessee-Campbell Clinic, 1211 Union Avenue, Suite 510, 38104, Memphis, TN, USA

    Jeffrey R. Sawyer MD

  10. Le Bonheur Children’s Hospital, 848 Adams Ave, 38103, Memphis, TN, USA

    Jeffrey R. Sawyer MD

Authors
  1. Chun Wai Hung MEng
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  2. Michael G. Vitale MD, MPH
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  3. Amer Samdani MD
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  4. Hiroko Matsumoto PhD
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  5. John T. Smith MD
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  6. Peter F. Sturm MD, MBA
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  7. Paul D. Sponseller MD, MBA
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  8. Scott J. Luhmann MD
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  9. Tricia Hilaire MPH
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  10. Ron El-Hawary MD, MSc
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  11. Jeffrey R. Sawyer MD
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Corresponding author

Correspondence to Jeffrey R. Sawyer MD.

Additional information

Author disclosures: CWH (none), MGV (personal fees and other from Biomet, personal fees from Stryker, outside the submitted work), AS (personal fees from DePuy, Ethicon, Globus Medical, Misonix, Stryker, and Zimmer Biomet, outside the submitted work), HM (none), JTS (personal fees from Biomet, DePuy, Ellipse Technologies, Globus Medical, and Spineguard, outside the submitted work), PFS (personal fees from DePuy, Medtronic Sofamor Danek, and NuVasive, outside the submitted work), PDS (personal fees from Biomet; personal fees and other from DePuy; personal fees from Globus Medical, outside the submitted work), SJL (personal fees from DePuy, Globus Medical, Medtronic Sofamor Danek, and Stryker, outside the submitted work), TSH (none), REH (personal fees and other from DePuy; other from Joint Solutions; personal fees and other from Medtronic; personal fees from Apifix, Wishbone Medical, and Springer, outside the submitted work), JRS (personal fees from DePuy, NuVasive, Elsevier Publishing, and Wolters-Kluwer, during the conduct of the study).

Funding: No funding was received in support of this study.

IRB approval: IRB approval was not required.

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Hung, C.W., Vitale, M.G., Samdani, A. et al. Outcomes of Primary and Conversion Magnetically Controlled Growth Rods Are Different at Two-Year Follow-up: Results of North American Release. Spine Deform 7, 829–835 (2019). https://doi.org/10.1016/j.jspd.2019.01.002

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  • DOI: https://doi.org/10.1016/j.jspd.2019.01.002

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