Biomechanical spinal growth modulation and progressive adolescent scoliosis--a test of the 'vicious cycle' pathogenetic hypothesis: summary of an electronic focus group debate of the IBSE.

Ian Af Stokes,R Geoffrey Burwell,Peter H Dangerfield

doi:10.1186/1748-7161-1-16

Ian Af Stokes, R Geoffrey Burwell + Show 1 more

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https://doi.org/10.1186/1748-7161-1-16

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Journal: Scoliosis and Spinal Disorders	Publication Date: Oct 18, 2006
Citations: 265	License type: cc-by

Affiliation: University of Vermont

Abstract

There is no generally accepted scientific theory for the causes of adolescent idiopathic scoliosis (AIS). As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate on knowledge of important topics. This has been designated as an on-line Delphi discussion. The text for this debate was written by Dr Ian A Stokes. It evaluates the hypothesis that in progressive scoliosis vertebral body wedging during adolescent growth results from asymmetric muscular loading in a "vicious cycle" (vicious cycle hypothesis of pathogenesis) by affecting vertebral body growth plates (endplate physes). A frontal plane mathematical simulation tested whether the calculated loading asymmetry created by muscles in a scoliotic spine could explain the observed rate of scoliosis increase by measuring the vertebral growth modulation by altered compression. The model deals only with vertebral (not disc) wedging. It assumes that a pre-existing scoliosis curve initiates the mechanically-modulated alteration of vertebral body growth that in turn causes worsening of the scoliosis, while everything else is anatomically and physiologically 'normal' The results provide quantitative data consistent with the vicious cycle hypothesis. Dr Stokes' biomechanical research engenders controversy. A new speculative concept is proposed of vertebral symphyseal dysplasia with implications for Dr Stokes' research and the etiology of AIS. What is not controversial is the need to test this hypothesis using additional factors in his current model and in three-dimensional quantitative models that incorporate intervertebral discs and simulate thoracic as well as lumbar scoliosis. The growth modulation process in the vertebral body can be viewed as one type of the biologic phenomenon of mechanotransduction. In certain connective tissues this involves the effects of mechanical strain on chondrocytic metabolism a possible target for novel therapeutic intervention.

Highlights

In the absence of any generally accepted scientific theory for the etiology of idiopathic scoliosis, treatment remains pragmatic with a very incomplete scientific basis
The text for this debate was written by Dr Ian Stokes who addresses the concept of mechanical modulation of vertebral body growth in the pathogenesis of progressive adolescent scoliosis generally attributed to the Hueter-Volkmann or Delpech effect [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25] in which constant pathologic strong pressure inhibits endochondral longitudinal growth while reduced compression accelerates growth [2,3,4]; pressure exerted eccentrically causes an active change in the direction of growth [2,5,6,7]
The simulations indicate that a substantial component of scoliosis progression during adolescent growth is biomechanically mediated

Summary

Introduction

In the absence of any generally accepted scientific theory for the etiology of idiopathic scoliosis, treatment remains pragmatic with a very incomplete scientific basis. Scoliosis 2006, 1:16 http://www.scoliosisjournal.com/content/1/1/16 means of increasing debate of knowledge on important topics. The text for this debate was written by Dr Ian Stokes who addresses the concept of mechanical modulation of vertebral body growth in the pathogenesis of progressive adolescent scoliosis generally attributed to the Hueter-Volkmann or Delpech effect [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25] in which constant pathologic strong pressure inhibits endochondral longitudinal growth while reduced compression accelerates growth [2,3,4]; pressure exerted eccentrically causes an active change in the direction of growth [2,5,6,7]. Since it is generally recognized that multi-level arthrodesis of the spine is not a desirable outcome, currently there is renewed interest in modifying vertebral growth by early surgical interventions [42,43,44] including stapling and, in young children, fusionless scoliosis surgery [45] which is being evaluated experimentally in animals [46,47,48]

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