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

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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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