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Lower limb amputation
The amputation level is chosen so that the stump heals and allows the best rehabilitation: the knee is preserved when possible, because below-knee amputation allows walking with a prosthesis at a much lower energy cost than above-knee amputation; in wet infection with sepsis an open (guillotine) amputation is done first to control infection, and only then a definitive amputation.
Why it matters in the exam
Questions deal with choice of level, timing and complications. The energy cost of walking rises by about 25% after below-knee amputation and by about 65% after above-knee amputation, so many older patients after above-knee amputation never walk again. Healing depends on blood supply: TcPO2 above 40 mmHg predicts good healing, and below 20 mmHg poor healing; a palpable popliteal or femoral pulse also supports the level. Partial foot amputations — toe, ray or transmetatarsal — preserve almost normal walking, but need good flow to the foot. Above-knee or through-knee amputation suits a non-ambulatory patient, a patient with a fixed knee contracture (above 15–20 degrees), or when blood supply to a below-knee stump is inadequate.
In below-knee amputation technique the tibia is left about 10–15 cm below the tibial tuberosity, its anterior edge is bevelled, the fibula is cut slightly higher, and the stump is covered with a long posterior myocutaneous flap. In a foot with wet gangrene, an abscess or sepsis an open ankle-level (guillotine) amputation or wide drainage is done first, and only when infection is controlled — a definitive amputation. Complications: stump non-healing and infection (sometimes requiring a higher amputation), knee or hip contracture, phantom pain, and significant mortality in the first month, higher after above-knee amputation. Preventing contracture: no pillow under the knee, and early extension exercises. Early rehabilitation and prosthetic fitting improve the outcome.
Before any amputation of an ischaemic limb, check whether revascularisation can save the limb or at least allow a lower amputation level.
Key points
- Preserve the knee when possible.
- TcPO2 above 40 — good healing.
- Guillotine in sepsis, definitive amputation later.
- Above knee — for a non-ambulatory patient or with contracture.
- Early rehabilitation.
Summary table
| Level | When suitable | Note |
|---|---|---|
| Toe, ray or transmetatarsal | Limited gangrene with good flow | Preserves almost normal walking |
| Below knee | Healthy knee, adequate stump blood supply | Walking energy rises by about 25% |
| Above knee or through knee | Non-ambulatory patient, knee contracture, poor flow | Energy rises by about 65% |
| Ankle-level guillotine | Wet gangrene or sepsis | First stage before definitive amputation |
A free exam question
?מה הפרוגנוזה למטופל עם איסכמיה קריטית של הרגל (the question as examined, in Hebrew)
- א. 50% ,תמותה בשנה 25% ( קטיעה משמעותית major amputation) בשנה
- ב. 25% ,תמותה בשנה 50% ( קטיעה משמעותית major amputation) בשנה
- ג. 50% תמותה ב ,שנה 50% ( קטיעה משמעותית major amputation) בשנה
- ד. 25% ,תמותה בשנה 25% ( קטיעה משמעותית major amputation) בשנה
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Sources
- Global Vascular Guidelines on the management of chronic limb-threatening ischemia (SVS/ESVS/WFVS), 2019 — Role of amputation
- Rutherford's Vascular Surgery and Endovascular Therapy, 10th edition (2022) — Lower extremity amputation: techniques and results
- VA/DoD Clinical Practice Guideline for Rehabilitation of Individuals with Lower Limb Amputation, 2017 — Recommendations
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.