Preclinical evaluation of posterior spine stabilization devices: can we compare in vitro and in vivo loads on the instrumentation?

Luigi la Barbera, Fabio Galbusera, Hans Joachim Wilke, Tomaso Villa

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: To discuss whether the standard test method for preclinical evaluation of posterior spine stabilization devices with an anterior support correctly describes the effect of two short-segment posterior stabilization techniques frequently used in clinical practice for the treatment of traumatic, degenerative and iatrogenic instabilities. Methods: A finite element study compared a validated instrumented L2–L4 segment undergoing standing, upper body flexion and extension to ISO 12189 standards model under a compressive load. A bridge instrumentation, with screws only at cranial and caudal levels, and a full stabilization, using screws at every level, are considered for both conditions. The internal loads on the spinal rod and the stress values on the implant are analysed in detail. Results: Using ISO model and a bridge stabilization construct allow to overstress the pedicle screw more than a full stabilization with respect to the corresponding L2–L4 segment undergoing upper body flexion, while the stress on the spinal rod is comparable. Choosing softer/stiffer springs would involve higher/lower loads on every component. Conclusions: ISO model predicts the effects of using both a full and a bridge posterior instrumentation. The study justifies the use of both conditions during in vitro reliability tests to achieve meaningful results easy to compare to clinically relevant loading modes and known in vivo failure modes.

Original languageEnglish
Pages (from-to)200-209
Number of pages10
JournalEuropean Spine Journal
Volume26
Issue number1
DOIs
Publication statusPublished - 2017

Keywords

  • Anterior support
  • ASTM F1717
  • Bridge instrumentation
  • Finite element
  • ISO 12189
  • Preclinical evaluation
  • Spine stabilization
  • Standard

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

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