Abstract
Summary Statement
The spinal cord showed marked sensibility to acute compression causing complete and irreversible injury. On the contrary, the spinal cord has more ability for adaptation to slow progressive compression mechanisms having the possibility of neural recovery after compression release.
Introduction
The aim of this experimental study was to establish, by means of neurophysiologic monitoring, the degree of compression needed to cause neurologic injury to the spinal cord, and analyze whether these limits are different making fast or slow compression.
Material and Methods
Spinal cord was exposed from T7 to T11 in 5 domestic pigs with a mean weight of 35 kg. The T8 and T9 spinal roots were also exposed. A pair of sticks, attached to a precise compression device, was set up to both sides of the spinal cord between T8 and T9 roots. Sequentially, the sticks were approximated 0.5 mm every 2 minutes causing progressive spinal cord compression. An acute compression of the spinal cord was also reproduced by a 2.5 mm displacement of the sticks. Cord to cord motor evoked potentials were obtained with two epidural catheters, stimulating proximal to T6 and recording below the compression level, distal to T10, for each sequential approach of the sticks.
Results
The mean width of the dural sac was 7.1 mm. For progressive compression, increasing latency and decreasing amplitude of the evoked potentials were observed after a mean displacement of the sticks of 3.2 ± 0.9 mm, the evoked potential finally disappearing after a mean displacement of 4.6 ± 1.2 mm. The potential returned 16.8 ± 3.2 minutes after the compression was stopped in every case. The evoked potentials immediately disappeared after an acute compression 2.5 ± 0.3 mm, without any sign of recovering after 30 minutes.
Conclusion
The proposed experimental model replicates the mechanism of a spinal cord injury caused by medially displaced screws into the spinal canal, causing therefore lateral compression to the spinal cord. The spinal cord showed marked sensibility to acute compression, which caused complete and irreversible injury. On the contrary, the spinal cord has more ability for adaptation to progressive and slow compression mechanisms. From a clinical point of view, it seems mandatory to avoid maneuvers of rapid mobilization or acute, even minimal, contusions of the thoracic cord.
