Journal of - Spinal Research Foundation

SPINAL RESEARCH FOUNDATIONSpines in Motion GlossarySpine Biomechanics: PerspectivesGlobal: The global perspective is all-inclusive; the entire skull,spinal column, and pelvis are in view.Regional: The regional perspective is more narrowly focused; however,the region varies in size, it could include the entire cervicothoracicregion (C1-T12), just the thoracic region (T1-T12), or onlymultiple thoracic segments (T4-T9).Local: The local perspective usually pertains to a single motionsegment-the functioning unit of the spine.GLOBALREGIONAL LOCALCompressionLoadPivot PointTensionGlobal Biomechanics: ForcesForce: An action applied to a body which results in a change of stateor movement.Compression: A force that acts along the axis of the spine to pushmaterial together; the intervertebral discs act as shock absorbers andare flattened by compressive forces, such as gravity.Tension: A force that acts along the axis of the spine to pull materialapart, elongating the material; vertebral bodies and intervertebral discsare elongated by tension forces.Shear: A force acting perpendicular to the surface it is acting on; ashear force acting on the spine may result in spondylolisthesis (anteriordisplacement or forward slippage of a vertebra in relation to the vertebrabelow).Torque: Rotational forces perpendicular to the axis of the spine; anexample would be twisting from side to side; excessive torque canresult in torsional fractures.Creep: The gradual deformation of a body due to a constant applicationof a load over a period of time; deformed intervertebral discs mayoccur as a result of continual loads and stress placed on the spine.Relaxation: A reduction in stress or load overtime, but strain anddeformation remains constant.47 Journal of The Spinal Research Foundation FALL 2012 VOL. 7 No. 2