After making an incision on the skin, longitudinal incisions with approximately 2–3 mm depth were made on the left and right side of the spinous processes of the vertebrae T6-T12 using scalpel #10. The paravertebral muscles were then gently pulled away from the spine, without any further incision or damage to the muscles. With retractors holding the muscle aside, laminectomy was performed using a Zeiss operating microscope, by cutting and removing the lamina at T8 to expose the dorsal surface of the spinal cord. Stabilization clamps were placed at the posterior spinous processes of the vertebrae T6 and T12 to support the vertebral column during impact.
The exposed spinal cord was then contused at the thoracic vertebra T8 using the NYU-MASCIS (New York University - Multicenter Animal Spinal Cord Injury Study) weight-drop impactor11 (link). This device consists of a 10g rod with a flat circular impact surface of diameter 2mm, which is slightly less than that of the rodent spinal cord (body weight >200g) to clear the edges of the vertebral canal as the impactor hits the cord. This also ensures that the entire impact surface is in complete contact with the cord during the contusion, so that all the energy from the weight drop is transferred to the spinal cord parenchyma. This impactor rod was directed towards the midline of the exposed spinal cord and was released from a height of 6.25 mm (n=3), 12.5 mm (n=3), 25 mm (n=3) or 50 mm (n=3), producing more severe neurologic injuries with increasing height. The control group (n=3) underwent laminectomy only. The impactor device was connected to a software Impactor v. 7.0 on a computer, which displayed the impact trajectory curves using the impactor and vertebral position sensors and the cord contact sensor11 (link). It also computed the actual height, time and velocity of the impact. Only rats with <0.05% variation in these values were considered for this study.
After injury, the muscles were sutured in layers and the skin closed with metal wound clips. Gentamycin (5 mg/kg, intramuscular; Abbott Laboratories, North Chicago, IL) was administered immediately post-surgery and then daily for 7 days. The analgesic, Buprenex (0.3 mg/kg, subcutaneous; Reckitt Benckiser, Richmond, VI), was delivered post-surgery and daily for 2 days. After surgery, their bladders were expressed regularly with no complications or other infections to report. No sign of autotomy or autophagy were observed. The rats were maintained for 7 weeks after injury.
The exposed spinal cord was then contused at the thoracic vertebra T8 using the NYU-MASCIS (New York University - Multicenter Animal Spinal Cord Injury Study) weight-drop impactor11 (link). This device consists of a 10g rod with a flat circular impact surface of diameter 2mm, which is slightly less than that of the rodent spinal cord (body weight >200g) to clear the edges of the vertebral canal as the impactor hits the cord. This also ensures that the entire impact surface is in complete contact with the cord during the contusion, so that all the energy from the weight drop is transferred to the spinal cord parenchyma. This impactor rod was directed towards the midline of the exposed spinal cord and was released from a height of 6.25 mm (n=3), 12.5 mm (n=3), 25 mm (n=3) or 50 mm (n=3), producing more severe neurologic injuries with increasing height. The control group (n=3) underwent laminectomy only. The impactor device was connected to a software Impactor v. 7.0 on a computer, which displayed the impact trajectory curves using the impactor and vertebral position sensors and the cord contact sensor11 (link). It also computed the actual height, time and velocity of the impact. Only rats with <0.05% variation in these values were considered for this study.
After injury, the muscles were sutured in layers and the skin closed with metal wound clips. Gentamycin (5 mg/kg, intramuscular; Abbott Laboratories, North Chicago, IL) was administered immediately post-surgery and then daily for 7 days. The analgesic, Buprenex (0.3 mg/kg, subcutaneous; Reckitt Benckiser, Richmond, VI), was delivered post-surgery and daily for 2 days. After surgery, their bladders were expressed regularly with no complications or other infections to report. No sign of autotomy or autophagy were observed. The rats were maintained for 7 weeks after injury.
