Study on the safe range of shortening of the spinal cord in canine models.

Abstract

Experimental dog model of spinal cord shortening. To clarify the relationship between the amount of shortening of the spinal cord and the degree of injury it may induce, and to determine the safe range of the shortening. Xi'an Jiaotong University, China. Thirty adult dogs were randomly allocated to five groups. Dogs in Group A (sham operation control) underwent spondylectomy to have two-thirds of the thirteenth thoracic segment (T13) resected, without bone-to-bone contact of the adjacent vertebral bodies. Those in Group B, C, D and E had one-third, half, two-thirds and total of their T13 resected, respectively, with bone-to-bone contact. Somatosensory-evoked potentials (SEP) and spinal cord blood flow (SCBF) were detected. The histopathologic changes of spinal cord tissue were observed by hematoxylin and eosin stain and electron microscope. The shortening of the spinal cord < half of a vertebral segment height caused a reversible change of SEP. Whereas, the changes resulted from the shortening of more than two-thirds of a vertebral segment height did not return to the normal level. SCBF increased temporarily when the shortening was within two-thirds of a vertebral segment height; whereas, it decreased progressively when the length of the shortening was equal to one vertebral segment height. More serious hemorrhage occurred as the shortening increased. Shortening of half of a vertebral segment height will not induce spinal cord injury (SCI), while that between half and two-thirds of a vertebral segment may lead to incomplete SCI.