A review of biomechanics of the central nervous system - Part III: Spinal cord stresses from postural loads and their neurologic effects

Objective: To review literature pertaining to neurologic disorders stemming from abnormal postures of the spine. Data Collection: A hand search of available reference texts and a computer search of literature from Index Medicus sources was performed, with special emphasis placed on spinal cord stresses and strains caused by various post ural rotations and translations of the skull, thorax, and pelvis. Results: Spinal postures will often deform the neural elements within the s pinal canal. Spinal postures can be broken down into four types of loading: axial, pure bending, torsion, and transverse, which cause normal and shear stresses and strains in the neural tissues and blood vessels. Prolonged st resses and strains in the neural elements cause a multitude of disease proc esses. Conclusion: Four types of postural loads create a variety of stresses and s trains in the neural tissue, depending on the exact magnitude and direction of the forces. Transverse loading is the most complex load. The stresses a nd strains in the neural elements and vascular supply are directly related to the function of the sensory, motor, and autonomic nervous systems. The L iterature indicates that prolonged loading of the neural tissue may lead to a wide variety of degenerative disorders or symptoms. The most offensive p ostural loading of the central nervous system and related structures occurs in any procedure or position requiring spinal flexion. Thus flexion tracti on, rehabilitation positions, exercises, spinal manipulation, and surgical fusions in any position other than lordosis for the cervical and lumbar spi nes should be questioned.