Biomechanical models to study spinal phenotypes

Introduction

Back and neck pain involve pathologies of all spinal tissues that result in functional changes to spinal biomechanics and biology. As spine research advances, it has become clear that many clinical definitions of spinal pathologies have limited relationships to painful conditions, motivating a need for more precise phenotypic characterizations. One of the most clear examples of this is intervertebral disc (IVD) degeneration (see Chapter 6 ), since abnormalities in disc magnetic resonance imaging (see Chapter 5 ) are common in asymptomatic controls and do not always correlate with clinical symptoms in patients [ , ]. Consequently, IVD degeneration is commonly considered to have similar characteristics of aging and often considered an aging phenomenon and is accelerated in some [ ]. More precise definitions of functional pathological phenotypes are required to describe better the pathological changes associated with disability and pain and to distinguish those changes from aging phenomena. Modeling these specific phenotypes for biomechanical testing is therefore critical to the study of spinal pathology

The purpose of this chapter is to describe biomechanical models to study spinal phenotypes, which include tissue and structural biomechanical models, cell and organ culture, and finite element modeling. We first describe IVD degeneration phenotypes and then describe the biomechanical, and to a lesser extent the biological, changes involved in distinct injuries that simulate these spinal pathology conditions. We describe findings that have informed pathophysiology known to be associated with IVD degeneration to clarify important biomechanical characteristics required to repair these degenerative conditions.