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Metallosis is commonly associated with magnetically controlled growing rods; results from an independent multicentre explant database

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Abstract

Purpose

Determine the incidence of metallosis around MAGEC rods.

Methods

A multicentre explant database was searched to identify cases with complete intraoperative findings at rod removal. Surgeons removing rods detailed the presence or absence of tissue metallosis associated with rods. More recently surgeons measured the ‘length’ of tissue metallosis. Prior to rod disassembly, the majority underwent testing with an external remote controller (ERC). The impact of clinical and explant variables on metallosis was assessed.

Results

Sixty-six cases were identified. Mean age at insertion was 8.1 ± 2.3 years with mean duration of implantation 37.6 ± 15.1 months.

Tissue metallosis was noted at revision surgery in 52/66 cases (79%). Metallosis was noted more commonly when rods were removed during fusion surgery than rod removal/exchange (97% vs. 58% (p =  < 0.01)). The mass at insertion was greater in cases with metallosis (25.9 ± 7.8 kg vs. 21.1 ± 6.2 kg, p = 0.04).

Length of tissue metallosis was reported for 45 rods, median 9 cm (range 1–25). Metallosis was noted in 43/59 (73%) rods that produced no force and 22/30 (73%) rods that produced some force on ERC activation (p = 0.96). Wear debris was found within the actuator in all rods, and all but 3 rods had damaged O-rings.

Conclusion

MAGEC rods are associated with tissue metallosis in the majority of cases. It is seen with functional rods as well as failed rods and appears related to wear debris within the actuator and high rates of O-ring failure. Until the implications of metal debris in children are known, we urge caution with the use of this implant.

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Acknowledgements

The authors wish to thank the surgeons contributing cases to this study from Bristol, Belfast, Edinburgh, Exeter, Leeds, Oxford and Sheffield in the UK, Aarhus in Denmark, Basel in Switzerland and Vancouver in Canada. We thank the manufacturers of the implant, NuVasive Specialised Orthopaedics, San Diego, CA, who kindly provided a testing jig but did not influence the conduct of this independent study.

Funding

No funding was received to assist with the preparation of this manuscript.

Author information

Authors and Affiliations

  1. Great North Children’s Hospital, Royal Victoria Infirmary, Newcastle upon Tyne, UK

    Paul R. P. Rushton, David Fender & Andrew J. Bowey

  2. School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne, UK

    Simon L. Smith & Thomas J. Joyce

  3. Orthopaedic Spinal Surgeon, Newcastle upon Tyne, UK

    Michael J. Gibson

Authors
  1. Paul R. P. Rushton
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  2. Simon L. Smith
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  3. David Fender
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  4. Andrew J. Bowey
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  5. Michael J. Gibson
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  6. Thomas J. Joyce
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Contributions

Gibson MJ and Joyce TJ helped in conceptualization; Rushton PR, Joyce TJ, Smith S contributed to methodology; Rushton PR, Joyce TJ, Smith SL formally analyzed and investigated the study; Rushton PR, Joyce TJ helped in writing—original draft preparation; Gibson MJ, Fender D, Bowey AJ helped in writing—review and editing.

Corresponding author

Correspondence to Paul R. P. Rushton.

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The authors have no relevant financial or non-financial interests to disclose.

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This is an observational study.

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Michael J. Gibson: Consultant Orthopaedic Spinal Surgeon (Retired).

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Rushton, P.R.P., Smith, S.L., Fender, D. et al. Metallosis is commonly associated with magnetically controlled growing rods; results from an independent multicentre explant database. Eur Spine J 30, 1905–1911 (2021). https://doi.org/10.1007/s00586-021-06750-2

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  • DOI: https://doi.org/10.1007/s00586-021-06750-2

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