After penetrating injury, knee dislocation or a displaced fracture near an artery, CT angiography shows occlusion, active extravasation, pseudoaneurysm, intimal flap or arteriovenous fistula — and the minor injuries that can be watched.
Orient first
- Hard signs (pulsatile bleeding, expanding haematoma, absent pulse) go to surgery; soft signs go to CTA.
- Knee dislocation injures the popliteal artery in a significant minority.
- Metallic fragments cause streak artefact — reconstruct thin and use MIP carefully.
Acquire the study
- CT angiography of the limb (arterial phase, bolus-tracked) with a delayed phase if the distal vessels are not opacified; 1 mm with MIP and curved reformats.
The manoeuvre
- Arterial phase: follow each artery through the injured zone on axial and curved reformats.
- Occlusion: its length in cm and distal reconstitution.
- Active extravasation and pseudoaneurysm size in mm.
- Intimal flap or focal narrowing (spasm vs injury).
- Early venous filling on the arterial phase (arteriovenous fistula).
What confirms it
- A direct arterial injury sign on CTA in the zone of injury.
What licenses you to exclude it
- Normal opacification through and beyond the injured segment excludes significant arterial injury.
The classic misread
- Streak artefact from fragments hiding a pseudoaneurysm.