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Porcine spine finite element model: a complementary tool to experimental scoliosis fusionless instrumentation

European Spine Journal volume 26, pages 1610–1617 (2017)Cite this article

Abstract

Purpose

Developing fusionless devices to treat pediatric scoliosis necessitates lengthy and expensive animal trials. The objective was to develop and validate a porcine spine numerical model as an alternative platform to assess fusionless devices.

Methods

A parametric finite element model (FEM) of an osseoligamentous porcine spine and rib cage, including the epiphyseal growth plates, was developed. A follower-type load replicated physiological and gravitational loads. Vertebral growth and its modulation were programmed based on the Hueter–Volkmann principle, stipulating growth reduction/promotion due to increased compressive/tensile stresses. Scoliosis induction via a posterior tether and 5-level rib tethering, was simulated over 10 weeks along with its subsequent correction via a contralateral anterior custom tether (20 weeks). Scoliosis induction was also simulated using two experimentally tested compression-based fusionless implants (hemi- and rigid staples) over 12- and 8-weeks growth, respectively. Resulting simulated Cobb and sagittal angles, apical vertebral wedging, and left/right height alterations were compared to reported studies.

Results

Simulated induced Cobb and vertebral wedging were 48.4° and 7.6° and corrected to 21° and 5.4°, respectively, with the contralateral anterior tether. Apical rotation (15.6°) was corrected to 7.4°. With the hemi- and rigid staples, Cobb angle was 11.2° and 11.8°, respectively, with 3.7° and 2.0° vertebral wedging. Sagittal plane was within the published range. Convex/concave-side vertebral height difference was 3.1 mm with the induction posterior tether and reduced to 2.3 with the contralateral anterior tether, with 1.4 and 0.8 for the hemi- and rigid staples.

Conclusions

The FEM represented growth-restraining effects and growth modulation with Cobb and vertebral wedging within 0.6° and 1.9° of experimental animal results, while it was within 5° for the two simulated staples. Ultimately, the model would serve as a time- and cost-effective tool to assess the biomechanics and long-term effect of compression-based fusionless devices prior to animal trials, assisting the transfer towards treating scoliosis in the growing spine.

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Acknowledgements

Funding was provided by Natural Sciences and Engineering Research Council of Canada (Industrial Research Chair program with Medtronic of Canada).

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Authors and Affiliations

  1. Department of Mechanical Engineering, Canada Research Chair in Orthopedic Engineering’ and NSERC-Medtronic Industrial Research Chair in Spine Biomechanics, Polytechnique Montreal, Station “Centre-ville”, P.O. Box 6079, Montreal, Quebec, H3C 3A7, Canada

    Bahe Hachem & Carl-Eric Aubin

  2. Research Center, Sainte-Justine University Hospital Center, Montreal, Canada

    Bahe Hachem, Carl-Eric Aubin & Stefan Parent

  3. Department of Surgery, Faculty of Medicine, Université de Montréal, Montreal, Canada

    Carl-Eric Aubin & Stefan Parent

Authors
  1. Bahe Hachem
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  2. Carl-Eric Aubin
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Correspondence to Carl-Eric Aubin.

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No conflict of interest with the presented work included in the study.

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Hachem, B., Aubin, CE. & Parent, S. Porcine spine finite element model: a complementary tool to experimental scoliosis fusionless instrumentation. Eur Spine J 26, 1610–1617 (2017). https://doi.org/10.1007/s00586-016-4940-3

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  • DOI: https://doi.org/10.1007/s00586-016-4940-3

Keywords

  • Scoliosis
  • Growth modulation
  • Finite element model
  • Fusionless implant
  • Experimental scoliosis