In a firearm injury, what is the term used to describe the temporary cavity formed by the passage of a high-velocity projectile through tissue?

Explanation

## Cavitation in Firearm Injuries ### Definition and Mechanism **Key Point:** The temporary cavity is the transient space created by the radial displacement of tissue as the projectile passes through. It collapses within milliseconds after the projectile exits, but causes significant tissue damage through compression and shearing forces. ### Types of Cavities #### Permanent Cavity - The actual tract left behind by the bullet - Diameter approximately equal to the bullet diameter - Persists after wound closure - Contains devitalized tissue - Relatively small and linear #### Temporary Cavity - Transient expansion of tissue perpendicular to the bullet's path - Forms due to the kinetic energy transfer from the projectile - Collapses within milliseconds - Causes significant tissue damage through: - Compression - Shearing forces - Cavitation (bubble formation and collapse) - Diameter can be 10–40 times larger than the permanent cavity - Responsible for most of the tissue destruction in high-velocity injuries ### Comparison Table | Feature | Permanent Cavity | Temporary Cavity | | --- | --- | --- | | Duration | Persistent | Transient (milliseconds) | | Diameter | ≈ Bullet diameter | 10–40× bullet diameter | | Visibility | Visible on dissection | Collapses; not visible | | Tissue damage | Direct contact damage | Compression, shearing, cavitation | | Clinical significance | Marks bullet path | Causes most tissue injury | **High-Yield:** High-velocity projectiles (rifle bullets, >2000 fps) create large temporary cavities and cause extensive tissue damage. Low-velocity projectiles (handguns, <1500 fps) create minimal temporary cavities. **Clinical Pearl:** The temporary cavity is why high-velocity rifle injuries are far more destructive than handgun injuries, even if the permanent cavity diameter is similar. Vital organs in the path of the temporary cavity may be damaged even if not directly traversed by the bullet. **Mnemonic:** **TEMP** for Temporary cavity — **T**ransient, **E**xpands radially, **M**illiseconds duration, **P**erpendicular to path.