Abdominal Aortic Aneurysm (AAA) and Trauma: Rupture Risk, Fall Mechanics, and Screening

An abdominal aortic aneurysm (AAA) is a focal dilation ≥3 cm (or 1.5× normal aortic diameter). Rupture is catastrophic (80–90% mortality). Falls do not cause AAA but can precipitate rupture of an existing aneurysm.

Rupture Mechanics

• Wall stress (Laplace’s law): σ = (P × r) / t. Larger radius (r) and higher pressure (P) increase stress; thinning wall (t) compounds risk.
• Trauma (fall, MVC) → sudden BP surge + direct compression → exceeds wall tensile strength → rupture.
• Most ruptures occur spontaneously (no trauma) at diameter ≥5.5 cm (men) or ≥5.0 cm (women).

Risk Factors for AAA Development

• Age ≥65 (screening threshold)
• Male sex (4:1 M:F)
• Smoking (strongest modifiable; dose-dependent)
• Hypertension, atherosclerosis, hyperlipidemia
• Family history (1st-degree relative: 12–15% risk)
• Genetic: Marfan, Ehlers-Danlos, Loeys-Dietz (younger onset)
• COPD, PAD, coronary disease

Clinical Presentation of Rupture

• Classic triad (only 50%): Severe abdominal/back/flank pain + hypotension + pulsatile mass.
• Syncope, diaphoresis, nausea, groin radiation.
• “Contained” rupture: retroperitoneal hematoma → pain, stable vitals initially; may decompress → free rupture.

Screening & Surveillance

• US screening: Men 65–75 ever-smokers (USPSTF Grade B); selective for never-smokers/family history.
• Surveillance intervals: 3.0–4.4 cm q2–3 yrs; 4.5–5.4 cm q6–12 mos; ≥5.5 cm → repair referral.
• Repair: EVAR (endovascular) preferred if anatomy suitable; open repair for complex anatomy/young patients.

Fall Prevention in Known AAA

• Home safety modifications, balance training, medication review (antihypertensives, sedatives).
• Medical alert bracelet; educate caregivers on rupture signs.

AAA is asymptomatic until rupture; screening and risk factor modification are lifesaving.