Can a foot amputation be performed instead of a below-knee amputation?

Foot Amputation vs. Below-Knee Amputation

Yes, foot amputation (minor amputation at the inframalleolar level) should be performed instead of below-knee amputation whenever feasible, as it preserves maximal functional ability and significantly improves quality of life by maintaining the knee joint and allowing better mobility with or without a prosthesis. 1

Primary Principle: Preserve Maximum Limb Length

The 2024 ACC/AHA guidelines explicitly state that evaluation by a multispecialty care team should assess for the most distal level of amputation that facilitates healing AND provides maximal functional ability. 1 This is a Class I, Level B-NR recommendation—the strongest level of evidence available.

The goal is preservation of a functional limb with a shoeable foot whenever ambulation is anticipated. 1 Below-knee amputation results in significantly higher quality of life compared to above-knee amputation, and by extension, foot-level amputation preserves even greater function than below-knee amputation. 1

When Foot Amputation is Appropriate

Clinical Requirements for Minor (Foot-Level) Amputation:

• Adequate perfusion to support healing at the foot level 1, 2
• Absence of extensive necrosis beyond the forefoot 1
• Controlled infection that does not extend proximally into the leg 1
• Patient is ambulatory or expected to ambulate after healing 1

Specific Foot-Level Amputation Options:

The 2024 guidelines note that when clinically appropriate using a team-based approach, minor amputation below the malleolus may be possible for patients in whom continued ambulation is anticipated. 1 Options include:

• Toe amputations for localized necrosis 2
• Transmetatarsal amputation for forefoot involvement 3
• Chopart or Lisfranc amputations for midfoot disease 3

Important caveat: The guidelines acknowledge conflicting evidence regarding the comparative benefit of different foot-level amputations relative to functional below-knee amputation. 1 However, the principle remains: preserve as much limb as possible that will heal and remain functional. 1

When Below-Knee Amputation is Necessary Instead

Absolute Indications for Below-Knee Over Foot Amputation:

1. Life-threatening infection with sepsis requiring immediate source control 1
2. Extensive necrosis or infectious gangrene involving the hindfoot or ankle 1
3. Severe ischemia where foot-level amputation will not heal despite revascularization 2
4. Failed foot-level amputation with non-healing or progressive infection 1

The Staged Approach:

For severe infections, guillotine ankle amputation followed by definitive below-knee amputation is associated with significantly lower failure rates (97% primary healing) compared to primary definitive below-knee amputation (78% primary healing, 11% requiring revision to above-knee). 4, 5 This staged approach allows:

• Rapid infection decompression 5
• Minimized blood loss 5
• Better wound healing outcomes 4

Critical Decision-Making Algorithm

Step 1: Assess Revascularization Potential

• If revascularization is possible: Perform revascularization FIRST, then assess for most distal amputation level 1, 2
• If no revascularization option: Consider primary major amputation only if extensive necrosis or life-threatening infection 1

Step 2: Evaluate Healing Potential at Foot Level

• Measure perfusion: Foot TcPO2 and toe pressure help delineate amputation zone 1
• Assess nutritional status: Serum albumin, total lymphocyte count, and Doppler ischemic index predict healing (92% healing rate when all factors adequate vs. 38.5% when deficient) 6

Step 3: Determine Infection Extent

• Localized to foot: Proceed with foot-level amputation after debridement 1, 2
• Ascending infection or sepsis: Consider staged guillotine approach or immediate below-knee amputation 4, 5

Step 4: Consider Patient Factors

• Ambulatory potential: Strongly favors foot preservation 1
• Diabetes with neuropathy: Requires aggressive follow-up but does not preclude foot amputation 1
• Non-ambulatory with severe comorbidities: May warrant primary below-knee or even above-knee amputation 1

Post-Amputation Management Requirements

For patients undergoing minor (foot-level) amputation, a customized follow-up program is mandatory (Class I recommendation): 1

• Local wound care 1
• Pressure offloading 1, 2
• Serial evaluation of foot biomechanics 1
• Therapeutic footwear 1, 2
• Patient education on self-surveillance 2

This intensive follow-up prevents wound recurrence, which is common in this population. 1

Quality of Life Considerations

Walking with a prosthesis and preserving the knee joint are the two outcomes with the greatest impact on quality of life among amputees. 1 Foot-level amputation:

• Allows full end-bearing 3
• Enables walking without prosthesis in some cases 3
• Minimizes loss of weight-bearing surface 3
• Preserves knee joint function 1

Below-knee amputation results in higher QOL than above-knee amputation, but foot preservation is superior to both when healing is achievable. 1

Common Pitfalls to Avoid

1. Performing below-knee amputation without multispecialty evaluation when foot-level amputation might heal 1
2. Attempting foot-level amputation in severe ischemia without revascularization first 1, 2
3. Inadequate follow-up after minor amputation leading to wound recurrence 1
4. Delaying necessary amputation in life-threatening infection while attempting prolonged antibiotic therapy 1