An In-vitro Study on the Effects of Spinal Canal Curvature on Cord Interstitial Pressure during Spinal Cord Distraction

Abstract

Study Design

This is an in-vitro study examining the effect of spinal canal curvature on spinal Cord Interstitial Pressure (CIP) during porcine spinal cord distraction. In this study we examined CIP developed in spinal cords during distraction in three conditions: 1) linear cord distraction (stretch) 2) simulated 45 degree scoliotic curve and 3) simulated 90 degree scoliotic curve.

Summary of Background Data

Spinal cord distraction is a known cause of spinal cord injury (SCI). Several papers published on the pathophysiology of the cord distraction injury suggest that the underlying mechanism of injury is a micro-vascular ischemic event⁴. We have previously described an increase in CIP with spinal cord distraction,^12,18 and have shown that spinal cord distraction can lead to spinal cord injury in live animal experiments¹³. Distraction spinal cord injury is known in scoliosis correction but rare in other spine injuries. With this experiment we wish to determine if simulated spinal curvature may potentiate the spinal cord distraction elevation in CIP noted during our experiments.

Objectives

To determine if increasing degrees of spinal curvature lead to increasing CIP during in-vitro spinal cord distraction.

Methods

Ten freshly thawed porcine spinal cords were tested in a saline bath in linear, 45° degree and 90° degree curved surfaces while CIP was monitored using the modified Whitesides technique²⁷. Multiple linear regressions were then performed.

Results

We noted a close correlation between applied tension (T) and CIP. The greatest pressure elevations were noted for the 90° curve mode, intermediate elevations were noted for the 45° curve modes and the smallest pressure elevations were noted for the linear mode of distraction (p <  = 0.05).

Conclusion

High CIP can be achieved through spinal cord distraction. This CIP is not only directly proportional to tension, but also proportionally increased by the degree of spinal curvature. This may suggest that spinal curvature may tend to increase generated CIP during distraction, and be a potentiating factor for spinal cord injury during scoliosis correction.