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INTRODUCTION
The mechanisms of injury from gunshot have been categorized[4]
into four distinct processes:
i) direct missile contact with tissue,
causing disruption of the tissue;
ii) high over-pressure in the immediate vicinity of the projectile,
which crushes the tissue;
iii) expansion of the temporary cavity after passage of the projectile,
stretching and tearing tissue, and
iv) Rayleigh-Taylor instability of the temporary cavity upon collapse,
tearing and disrupting the cavity wall.
Laboratory experiments with animals[5]-[7]
have demonstrated that
gunshot injury can occur in tissue
remote from the trajectory of the missile.
It has been demonstrated[5]
that remote injury correlates with measurements
of pressure waves generated by bullet impact.
However, this mechanism has been disputed[8]
on the grounds that
in early experiments[9]
no injury to human red blood corpuscles
or whole frog hearts
due to the pressure waves generated by the passage of bullets
was observed.
On the other hand, it has been shown[10]
that
cultures of nerve cells which are far enough from bullet trajectories
that they are not directly involved in the temporary cavity suffer
delayed injury.
Subsequently it was also shown[11]
that
nerve cells are more vulnerable to remote injury
than other types of cells.
We present a case in which a localized spinal cord injury followed
a gunshot wound without entry of bullet fragments into the spinal
canal.
We postulate that wave focusing by thoracic vertebrae can concentrate
energy into the spinal canal,
with consequent injury to the spinal cord.
brad@galcit.caltech.edu