An experimental study on chronic compression injury of the spinal cord due to kyphotic deformity.

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In order to evaluate the influence of the traction on the spinal cord function due to ischemic changes of the spinal cord, the spinal cord blood flow and the spinal cord evoked potentials in response to strong and weak stimulation was measured in mature rabbits under spinal column traction. In animals subjected to a traction corresponding to approximately 32% of the vertebral body length, the amplitude of evoked potential in weak stimulation increased transiently, whereas the amplitude in strong stimulation declined slowly. The blood flow at this time was decreased to 10ml/min/100g, suggesting spinal cord dysfunction. For the diagnosis of spinal cord injury due to ischemia, observation of the amplitude changes in response to weak stimulus appeared to be indispensable even if the amplitude changes in strong stimulation remained within a safe range.By posterior ( posterior method ) or anterior ( anterior method ) manipulation of the rabbit spinal column, an animal model with kyphotic def … More ormity with a constant pressure on the spinal cord was prepared. The dynamic compression by the spinal deformity appeared to be the major cause of spinal cord inixiry, whereas the static pressure appeared to be responsible for the injury in the anterior method. None of these models showed paralysis, probably serving as the model for the initial stage of chronic compression spinal cord damage. However, in all cases, measurement of the spinal cord evoked potential revealed some potential changes. This method thus appeared to be very useful for the detection of subclinical spinal cord injury due to chronic compression. The prolongation of conduction time was more pronounced in the posterior method, although the decrease in amplitude appeared to be more pronounced in the anterior method. It is considered that demyelination is readily occurred on dynamic compression such as the posterior method, while the static compression as in the anterior method tends to cause axonal degeneration. Qualitative difference in spinal cord injury may be caused by the differences in the mode of compression itself, such as the presence or absence of the mobility of the kyphotic portion, or by differences in the secondary factors associated with each compression modality. Less