Classification Systems in Vascular Surgery
MRCS Part A & B — Comprehensive Study Notes
Fontaine Classification — Chronic Limb Ischaemia
The Fontaine classification (1954) is a widely used clinical staging system for chronic lower limb ischaemia based on symptoms. Four stages (I–IV), with stage II further subdivided.
Asymptomatic
Haemodynamically significant arterial disease detected on investigation (e.g., reduced ABPI) but no symptoms. Patient may note mild leg fatigue. Disease present but compensated by collateral circulation.
Mild Claudication
Intermittent claudication with walking distance >200 metres. Cramping leg pain (usually calf) on exercise that reliably resolves within minutes of rest. Mild limitation to daily activities.
Moderate-to-Severe Claudication
Claudication distance <200 metres. More significant functional limitation. May need to stop frequently during normal activities. Conservative management optimised; intervention considered if lifestyle is significantly impaired.
Rest Pain (Ischaemic Rest Pain)
Constant burning pain in the foot and toes at rest, especially at night. Pain is worse with leg elevation (gravity reduces perfusion) and better with dependency (patient hangs foot out of bed or sleeps in a chair). ABPI typically <0.4–0.5. Requires urgent revascularisation assessment.
Tissue Loss (Ulceration / Gangrene)
Ischaemic ulceration or gangrene. The limb is threatened. Without revascularisation, major amputation is inevitable. Stage IVa: minor tissue loss (ulcer, focal gangrene — toe/forefoot). Stage IVb: major tissue loss (forefoot or more extensive gangrene). ABPI <0.4; toe pressure <30 mmHg; TcPO₂ <10 mmHg.
Rutherford Classification — Chronic Limb Ischaemia
A more granular classification (7 categories: 0–6) used in clinical trials and research. More widely used in the USA and in academic literature. Note that Fontaine and Rutherford are clinically equivalent — knowing both increases exam marks.
| Category | Grade | Clinical Description | Fontaine Equivalent |
|---|---|---|---|
| 0 | 0 | Asymptomatic — no haemodynamic compromise on testing | I |
| 1 | I | Mild claudication | IIa |
| 2 | I | Moderate claudication | IIb |
| 3 | I | Severe claudication (pain <50 metres or at rest after exercise) | IIb |
| 4 | II | Ischaemic rest pain | III |
| 5 | III | Minor tissue loss — non-healing ulcer or focal gangrene with diffuse pedal ischaemia | IV (minor) |
| 6 | III | Major tissue loss — extending above the TM line; functional foot no longer salvageable | IV (major) |
Critical Limb Ischaemia (CLI) — Definition
CLI is defined as Rutherford categories 4–6 / Fontaine stages III–IV. Haemodynamic criteria (European consensus): ankle systolic pressure <50 mmHg, or toe pressure <30 mmHg with rest pain; or ankle systolic pressure <70 mmHg with ulceration/gangrene. Without revascularisation, 1-year major amputation rate is ~25% and 1-year mortality is ~20–25% (reflecting widespread cardiovascular comorbidity). The term CLI has largely been replaced by Chronic Limb-Threatening Ischaemia (CLTI) in more recent guidelines (Global Vascular Guidelines 2019), which incorporates the WIFI (Wound, Ischaemia, Foot Infection) classification.