ABSTRACT
The three main functions of the spine are to allow movement, to carry loads and to protect neural structures. The components responsible for the structure and function of the spine can be regarded as the spinal system. Movement in the spine is determined by the shape of the structures, i.e. the anatomy, and by neurological control. This movement is restricted in order to avoid neurological damage and to prevent deformity. In other words, the spine must be stable, as defined as follows by White and Panjabi (1990):
Clinical stability of the spine is the ability of the spine under physiological loads to limit patterns of displacement so as not to damage or irritate the spinal cord or nerve roots, and in addition to prevent incapacitating deformity or pain due to structural changes.
