Is the speed of chronic compression an important factor for chronic spinal cord injury rat model

Abstract Objective : To evaluate the effect of expansion speed on chronic compressive spinal cord injury in the rat. Methods : Thirty-six Sprague-Dawley rats were divided into four groups: a control group, a group receiving compressor in the C5–C6 epidural space with instant compression (group 1), and two other groups receiving water-absorbing polyurethane polymer sheets with two expansion speeds, which reached maximum volume in 2 h (group 2: fast expansion) or 24 h (group 3: slow expansion). A C6 laminectomy was performed in the control group. Neurological function, MRI, large motoneuron number in the ventral horn, and myelin staining intensity in the posterior funiculus were evaluated. Results : In the instant compression group, compression was confirmed on T 2 -weighted images by a hypointense signal change in the intramedulla. In the gradual compressive injury groups, large motoneuron number ( p 2 -weighted image, large motoneuron numbers, or myelin staining between the fast and slow expansion groups. Conclusion : Instant spinal cord compression caused acute injury. Gradual expansion compression induced reliable pathology and MRI characteristics consistent with chronic compressive spinal cord injury. The speed of expansion is not a significant problem for establishing a reliable model if the chronic compression is induced by gradual expansion.