Abstract
Study Design. In vitro study of the spinal cord tension and pressure relationships before and after thawing in 6 different spinal cord segment from 2 individual pigs.
Objectives. To determine if frozen and thawed spinal cord segments had different tension/cord interstitial pressure(CIP) relationships to fresh spinal cord segments. In addition, we will determine if the cord level, individual cord properties, and repeated CIP measurements affect the tension/CIP relationships.
Summary of Background Data. Spinal cord distraction is a known cause of spinal cord injury. Several articles published on the pathophysiology of the cord distraction injury suggest that the underlying mechanism of injury is a microvascular ischemic event. We have previously described an increase in CIP with spinal cord distraction, pressures average 23 mmHg at 1 kg loads.
Methods. Six cord segments harvested from 2 pigs contained cervical, thoracic, and lumbar segments, and underwent distraction using a series of 7 calibrated weights from 0 to 1000 g weight. The cords were measured at each level of distraction. The cords were then frozen at - 20 degrees C for a period of 2 weeks, and then thawed and retested. Multiple linear regression was then performed.
Results. There was no difference between the fresh and the frozen-thawed cords; there was statistical difference between the 2 pigs (18 mmHg) (P < 0.001). There are differences between the cervical and the thoracic cord segments (P < 0.001), and between cervical and lumbar cord segments (P = 0.056). There is a significant relation between the tension applied and CIP. Repeated trials showed no drift with repeated measures.
Conclusion. Freezing and thawing spinal cords has no effect on the CIP/tension curves. Cord interstitial pressure developed is dependant on cord tension, cord level, individual cord properties, but not on the number of repetitions carried out while testing the spinal cord.