Wall Tension in Surgical Planning

A Practical Guide to Biomechanical Decision-Making

Professor Atef Allam • Surgical Planning • Risk Assessment

Laplace's Law: The Foundation

T = P × r

T: Wall tension (N/m) • P: Pressure • r: Radius

Clinical Applications

🫀 Aortic Aneurysms

Risk Threshold: T > 120 N/m → High risk → Repair recommended

Progressive Risk Example:

AAA: r = 3 cm, P = 120 mmHg → T = 36 N/m (Low Risk)

Expands to r = 5 cm → T = 60 N/m (Intermediate)

With hypertension P = 180 mmHg → T = 90 N/m (High Risk)

Open Repair: High tension + complex anatomy
EVAR: Lower tension with suitable anatomy

⚡ Aortic Dissection

Higher tension zones (ascending) → Urgent surgery
Lower tension zones (descending) → Medical management if stable

🩸 Vein Grafts (CABG)

Veins in arterial pressure: ↑ r → ↑ T → Graft failure risk

Select thick-walled veins (saphenous)
Use arterial grafts (LIMA) when possible

Case Example: AAA Decision

Patient Data:

AAA diameter: 5.5 cm
BP: 160/90 mmHg
T = 160 × 2.75 = 44 N/m

Decision Matrix:

EVAR: Check anatomy, suitable for moderate tension
Open Repair: If tension >60 N/m or complex anatomy

Essential Surgical Principle

"Wall tension calculations transform abstract biomechanics into life-saving surgical decisions. Every major vascular intervention should consider tension thresholds alongside anatomic factors."