What are the best management strategies for a patient at risk of amputation below the knee level, potentially due to complications from diabetes or peripheral artery disease (PAD)?

Management of Patients at Risk for Below-Knee Amputation

For patients at risk of below-knee amputation from diabetes or peripheral artery disease, prioritize multispecialty team-based care with aggressive revascularization attempts before considering amputation, as limb salvage with revascularization achieves 80-85% limb salvage rates at 12 months compared to 50% mortality at 5 years in this population. 1

Immediate Risk Stratification and Assessment

Clinical Evaluation Priority

• Assess for life-threatening sepsis first - if present with advanced soft-tissue infection or severe metabolic derangements from extensive tissue necrosis, emergency primary amputation takes precedence over limb salvage to prevent death 1
• Measure ankle-brachial index (ABI) bilaterally - values ≤0.50 indicate severe PAD, and absolute ankle pressure ≤50 mmHg or toe pressure ≤30 mmHg suggest high amputation risk without revascularization 2
• Use WIfI (Wound, Ischemia, and foot Infection) classification to objectively document amputation risk and guide decision-making 1
• Evaluate the contralateral limb immediately with ABI measurement, as atherosclerotic disease is typically bilateral even when symptoms appear unilateral 2

Vascular Assessment Algorithm

• Obtain duplex ultrasound as first-line imaging to assess anatomy and hemodynamic status of lower extremity arteries 1
• If revascularization is being considered, proceed to CT angiography or magnetic resonance angiography 1
• For chronic limb-threatening ischemia (CLTI) with below-the-knee lesions, perform angiography including foot run-off before revascularization 1

Revascularization Strategy (Primary Approach)

When to Pursue Revascularization

Revascularization is indicated whenever feasible for limb salvage in CLTI, as it achieves limb salvage rates of 80-85% and ulcer healing in >60% at 12 months. 1

• Perioperative mortality is <5% and major systemic complications occur in approximately 10% of patients 1
• The goal is to restore direct pulsatile flow to at least one foot artery, preferably the artery supplying the anatomical region of the wound 1
• Both endovascular and open surgical approaches show similar major outcomes (healing, amputation, complications), so choice depends on lesion morphology and local expertise 1
• Even severely ischemic ulcers can heal without revascularization in approximately 50% of cases with aggressive local wound management 1

Contraindications to Revascularization

Avoid revascularization when the risk-benefit ratio is unfavorable 1:

• Patients who are severely frail, bedbound at baseline, or have short life expectancy (advanced age, untreatable cancer) 1
• Extensive tissue destruction rendering the foot functionally unsalvageable even after surgical resection 1
• Patients in persistent vegetative state or with severe chronic comorbidity preventing ambulation 1
• When revascularization cannot be physiologically tolerated due to severe comorbid conditions 1

Multispecialty Team-Based Care (Essential Component)

Multispecialty care team collaboration is essential and must include vascular specialists, podiatrists, wound care specialists, and diabetologists. 1

Team Composition and Roles

• Transfer patients to facilities with multispecialty teams when these services are unavailable locally, except in life-threatening sepsis requiring immediate amputation 1
• Engage foot care specialists (podiatrists) for longitudinal follow-up - Medicare data shows patients receiving multispecialty care including foot specialists had reduced amputation rates 1
• Implement comprehensive diabetes and medical comorbidity management at the time of amputation planning 1

Wound Management Protocol

• Perform frequent debridement as part of comprehensive care 1
• Provide biomechanical offloading with prescription shoes 1
• Ensure patient education about foot care, appropriate extremity pressure offloading, and foot surveillance examinations 1

Medical Optimization Before Amputation

Glycemic Control

• Hemoglobin A1c >8.1% independently increases odds of reoperation by 4.6-fold after below-knee amputation 3
• Achieve documented glycemic control with HbA1c <7% before planned amputation to minimize reoperation risk 1, 3
• Optimal glycemic control should be pursued to improve foot outcomes 1

Cardiovascular Risk Management

All patients require aggressive cardiovascular risk management as 5-year mortality is 50% due to coexistent coronary and cerebrovascular disease. 1, 2

• Prescribe antiplatelet therapy (aspirin or clopidogrel) 1
• Target LDL-C <1.4 mmol/L (<55 mg/dL) or at least 50% reduction, as these patients are at very high cardiovascular risk 1
• Consider combination therapy with low-dose rivaroxaban (2.5 mg twice daily) plus aspirin (100 mg daily) in patients without high bleeding risk 1
• Provide aggressive treatment of hypertension 1
• Support smoking cessation with comprehensive interventions including behavior modification, nicotine replacement, or bupropion 1

When Primary Amputation is Appropriate

Absolute Indications

• Life-threatening sepsis from foot infection requiring emergency amputation for sepsis control 1
• Severe metabolic derangements from extensive tissue necrosis 1

Relative Indications (After Revascularization Specialist Review)

• When revascularization is not an option and local wound management fails or pain is prohibitive 1
• Extensive tissue destruction that would result in a nonfunctional extremity even after revascularization 1
• Patient is nonambulatory or bedbound at baseline from chronic comorbidity 1
• Short life expectancy from advanced age or untreatable cancer 1

Primary amputation should only be considered after thorough review by an experienced revascularization specialist in consultation with the multispecialty care team and in discussion with the patient and family incorporating the patient's goals of care. 1

Amputation Level Selection

Minor Amputation Considerations

• When clinically appropriate using team-based approach, minor amputation below the malleolus may be possible for patients in whom continued ambulation is anticipated 1
• Conflicting evidence exists regarding comparative benefit of foot level amputation (transmetatarsal, Chopart, Lisfranc) relative to functional below-knee amputation 1

Major Amputation Realities

• 30-day mortality after below-knee amputation is 7.0% 4
• 38% of patients require unplanned reoperation within 1 year of below-knee amputation, with 12% not reaching 30 days without reoperation 3
• Wound complications and hospital readmission rates are high, reflecting burden of advanced cardiovascular disease, diabetes, residual infection, ongoing smoking, and other comorbidities 1

Critical Pitfalls to Avoid

• Do not proceed to amputation without evaluation by an experienced revascularization specialist - even "no-option" patients may have revascularization possibilities 1
• Do not perform amputation in patients with uncontrolled diabetes (HbA1c >8.1%) without first optimizing glycemic control, as reoperation risk increases 4.6-fold 3
• Do not neglect bilateral vascular assessment - the contralateral limb is at significant risk even when symptoms are unilateral 2
• Do not overlook renal insufficiency, cardiac issues, history of sepsis, steroid use, COPD, and increased age as independent predictors of mortality after below-knee amputation 4
• Do not fail to implement cardiovascular risk management, as 1-year mortality in CLTI patients is 25%, rising to 45% in those undergoing amputation 2

Post-Amputation Management

Immediate Post-Operative Care

• Initiate early pharmacological thromboprophylaxis with low molecular weight heparin after hemorrhage control 5
• Start antiplatelet therapy pre-operatively unless contraindicated, continuing indefinitely post-operatively 5
• Begin physical therapy early with modifications to avoid excessive stress on the surgical site 5

Long-Term Surveillance

• Patients who undergo minor (inframalleolar) amputation remain at risk for wound-related complications, infection, and future major amputation 1
• Provide customized prescription footwear recommended by specialists who understand proper fit and pressure reduction 1
• Conduct annual comprehensive foot evaluations for remaining limb and contralateral limb 1