Biomechanics of experimental spinal cord trauma

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Abstract
The biomechanics of the thoracic spinal cord and thorax in experimental trauma were studied in cats. Contusion of the T [thoracic] 5-6 level of the feline spinal cord was accomplished by the weight-dropping technique; various combinations of weights and heights were used; and force, deformation/displacement, deformation velocity, and acceleration of deformation were measured. Greater force was associated with larger weights. Force was directly related to the displacement of the spinal cord and of the spinal cord/thorax. The presence of a destruction point on the force-displacement curve was suggested and its apparent significance discussed. Maximum deformation of the spinal cord was 1.1 mm, while the spinal cord/thorax was displaced a maximum of 4.6 mm. Deformation of the spinal cord ranged between 22% and 33% of the anteroposterior spinal cord diameter. Maximum deformation of the spinal cord was not associated necessarily with a maximum velocity of deformation; the range of velocity of spinal cord deformation was 0.12-0.18 m/s. The relationship between velocity of deformation and force was a horizontal parabolic one. Greater force was required to obtain the same velocity of deformation of the spinal cord relative to that of the spinal cord/thorax unit. The mechanical alterations in the structures supporting the spinal cord account for a significant portion of the biomechanical measurements of the spinal cord previously reported in trauma was concluded. Since the force on the spinal cord and the thorax are the same, force may well be a most reasonable means of quantitating experimental spinal cord trauma.