Abstract
Purposes
Autofusion (AF) during growing rod (GR) instrumentation for early-onset scoliosis (EOS) has been reported, but AF incidence, causation, and clinical implications remain unknown. This article aims to (1) quantify frequency and severity of AF, (2) determine risk factors for AF, and (3) assess the influence of AF on final curve correction and spinal lengthening.
Methods
EOS patients were prospectively enrolled (2016–2021). Patients underwent evaluation, GR implantation, lengthenings, and posterior spinal fusion (PSF). Cobb angle and spinal length measurements were collected. AF was assessed and graded, with grades I–II being low-grade and III–V being high-grade. Exposure analysis quantified risk factors’ impact via odds ratios and Pearson regression correlates. Statistical significance was p ≤ 0.05 or ≥ 0.95.
Results
28 patients, with variable EOS diagnoses, were included. On average, GR were implanted at 8.54-year-old and lengthened over 4.66 years. 53.6% of patients received magnetically controlled GR (MCGR) and 46.4% traditional GR (TGR). The average construct bridged 13.4 levels. Over the lengthening period, for all indications, patients averaged 2.9 total open procedures. Curves corrected from 68.5º preoperatively to 35.3º after index GR to 35.6º after PSF. Spinal length increased from 30.0 cm preoperatively to 33.9 cm after index GR to 39.5 cm after PSF. AF grading was: 28.6% Grade I, 25.0% Grade II, 17.9% Grade III, 25.0% Grade IV, and 3.6% Grade V. Idiopathic EOS tended to have lower AF grades (p = 0.37). AF risk factors included GR age < 8 (10.4×, p = 0.01), any interval open procedures (6.3×, p = 0.05), and residual curve > 30º after index GR (13.7×, p = 0.02). Protective factors included preoperative spinal length of > 30.0 cm (0.11×, p = 0.01) and index MCGR (0.16×, p = 0.03). Maintenance of Cobb angles from index GR through PSF was relatively better in low-grade patients (p = 0.08). Spinal length gained was no different between low- and high-grade AF (p = 0.50).
Conclusions
This largest-to-date evaluation found AF is nearly ubiquitous in GR constructs, but with variable severity. Both risk factors and protective factors coincide with AF. Ultimately, even in high-grade AF, curve correction was maintained, and spinal lengthening was achieved.
Level of evidence
Level II—prospective cohort study.
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Data availability
The data that supports the findings of this study are available from the corresponding author, BM, upon reasonable request.
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Acknowledgements
The authors would like to acknowledge Nichole Leitsinger and Lindsay Schultz for their contributions to patient enrollment.
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No funding was received for this project.
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Bryan Menapace: made substantial contributions to the conception or design of the work and made substantial contributions to the acquisition, analysis, or interpretation of data. Bryan Menapace: drafted the work and revised it critically for important intellectual content. Bryan Menapace, Viral Jain and Peter Sturm: approved the version to be published. Bryan Menapace, Viral Jain and Peter Sturm: 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. Viral Jain and Peter Sturm: made substantial contributions to the conception or design of the work. Viral Jain and Peter Sturm: revised the work critically for important intellectual content.
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Menapace: none, Jain: none, Sturm: Nuvasive and Green Sun Medical shareholder advisory board.
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This research study was conducted retrospectively from data obtained for research purposes. We consulted extensively with the IRB of Cincinnati Children’s Hospital Medical Center who determined that our study did not need ethical approval. An IRB official waiver of ethical approval was granted from the IRB at Cincinnati Children’s Hospital Medical Center.
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IRB approved and attained from the parent and/or legal guardian at the time of study enrollment.
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Menapace, B., Jain, V. & Sturm, P. Autofusion in early-onset scoliosis growing constructs: occurrence, risk factors, and impacts. Spine Deform (2024). https://doi.org/10.1007/s43390-024-00853-8
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DOI: https://doi.org/10.1007/s43390-024-00853-8