Below-the-Knee Interventions for Peripheral Arterial Disease: Techniques, Challenges, and Outcomes

Below-the-knee (BTK) interventions represent one of the most challenging frontiers in endovascular therapy for peripheral arterial disease. These procedures target the distal popliteal, tibial, and peroneal arteries, which are characterized by small vessel diameter, diffuse disease, heavy calcification, and limited access options. Despite these challenges, BTK interventions have become increasingly important in the management of critical limb ischemia, particularly in diabetic patients who frequently present with infrapopliteal disease patterns. This comprehensive guide explores the unique aspects of below-the-knee interventions, including anatomical considerations, technical approaches, device selection, clinical outcomes, and emerging technologies in this specialized area of endovascular therapy.

Anatomical Considerations and Disease Patterns

Tibial Vessel Anatomy

Understanding the distal vascular bed:

• Anterior tibial artery:
• Originates at tibial-peroneal trunk
• Courses anteriorly through interosseous membrane
• Runs along anterolateral aspect of leg
• Continues as dorsalis pedis artery

• Primary supply to dorsum of foot

• Posterior tibial artery:

• Larger terminal branch of popliteal
• Descends posteromedially in deep posterior compartment
• Passes behind medial malleolus
• Divides into medial and lateral plantar arteries

• Primary supply to plantar foot

• Peroneal artery:

• Originates from tibial-peroneal trunk
• Descends along medial fibula
• Provides multiple muscular branches
• Communicates with anterior and posterior tibial arteries

• Often preserved in diabetes

• Pedal arch anatomy:

• Formed by dorsalis pedis and lateral plantar arteries
• Complete in approximately 70% of individuals
• Significant anatomical variations
• Critical for tissue perfusion
• Important endpoint for revascularization

Disease Distribution Patterns

Characteristic patterns in different populations:

• Diabetic pattern:
• Predilection for tibial vessels
• Relative sparing of pedal vessels
• Heavy calcification
• Long segment occlusions

• Multiple levels of disease

• Non-diabetic pattern:

• More proximal disease
• Shorter segment involvement
• Less calcification
• More focal lesions

• Better collateralization

• Anatomical challenges:

• Vessel diameters 2-3mm
• Extensive collateralization
• Anatomical variants
• Tortuous course
• Bifurcation involvement

Patient Selection and Preprocedural Assessment

Indications for Intervention

Appropriate patient selection:

• Clinical scenarios:
• Critical limb ischemia (rest pain, tissue loss)
• Non-healing ulceration
• Gangrene with salvageable tissue
• Severe lifestyle-limiting claudication (selected cases)

• Preparation for distal bypass

• Hemodynamic criteria:

• Ankle pressure <50 mmHg
• Toe pressure <30 mmHg
• TcPO2 <30 mmHg
• Flat-line pulse volume recordings

• Monophasic waveforms

• Anatomical considerations:

• Target vessel patency to foot
• Vessel diameter
• Lesion length
• Calcification burden
• Outflow status

Preprocedural Imaging

Comprehensive assessment:

• Duplex ultrasonography:
• Non-invasive initial assessment
• Vessel patency evaluation
• Flow characteristics
• Limited by calcification

• Operator-dependent

• CT angiography:

• Excellent spatial resolution
• Multiplanar reconstruction capabilities
• Calcium visualization
• Contrast and radiation considerations

• Limited in heavy calcification

• MR angiography:

• No radiation exposure
• Less affected by calcification
• Limited spatial resolution for distal vessels
• Contraindications (pacemakers, renal dysfunction)

• Overestimation of stenosis

• Digital subtraction angiography:

• Gold standard for planning
• Multiple projections essential
• Delayed imaging for collaterals
• Selective injections
• Consideration of CO2 angiography with renal dysfunction

Angiosome Concept

Targeted revascularization approach:

• Angiosome territories:
• Anterior tibial: dorsum of foot
• Posterior tibial: plantar foot and heel
• Peroneal: lateral ankle and heel
• Specific territories for each terminal branch

• Overlap zones between territories

• Direct vs. indirect revascularization:

• Direct: revascularization of artery supplying wound territory
• Indirect: revascularization of non-angiosome vessel
• Consideration of collateral networks
• Debate regarding outcomes difference

• Technical feasibility considerations

• Clinical application:

• Wound location assessment
• Target vessel selection
• Balanced with technical feasibility
• Consideration of collateral networks
• Integration with WIfI classification

Technical Approaches and Procedural Considerations

Access Strategies

Multiple options for reaching distal vessels:

• Antegrade common femoral access:
• Традиционен подход
• Better pushability and torquability
• Challenging in obese patients
• Steeper learning curve

• Closure device considerations

• Retrograde popliteal access:

• Prone or lateral position
• Useful for flush SFA occlusions
• Shorter distance to target lesions
• Risk of popliteal injury

• Compression challenges

• Pedal access:

• Dorsalis pedis or posterior tibial approach
• Ultrasound guidance essential
• Small sheathless systems
• Useful for retrograde crossing

• Limited to specific scenarios

• Transpedal retrograde access:

• Increasingly utilized
• 4Fr or smaller sheaths
• Ultrasound-guided puncture
• Complementary to antegrade approach
• SAFARI technique (Subintimal Arterial Flossing with Antegrade-Retrograde Intervention)

Crossing Strategies

Navigating complex occlusions:

• Intraluminal techniques:
• Hydrophilic wire escalation
• Support catheter use
• Tapered-tip catheters
• Specialized crossing wires

• Low-profile support catheters

• Subintimal approaches:

• Controlled dissection
• Re-entry considerations
• Limited dedicated re-entry devices for BTK
• Wire loop technique

• Parallel wire technique

• Retrograde crossing:

• Through pedal vessels
• Wire externalization
• Rendezvous techniques
• Through collaterals
• Management of access site

Balloon Angioplasty Techniques

Mainstay of BTK intervention:

• Conventional angioplasty:
• Appropriate sizing (typically 2-3mm)
• Long inflation times (3+ minutes)
• Sequential inflations
• Low-profile systems

• Prolonged inflation for dissection

• Specialty balloons:

• Scoring balloons
• Cutting balloons
• Focal-force balloons
• Ultra-high pressure balloons

• Application for specific lesion types

• Drug-coated balloons:

• Mechanism of action
• Налични платформи
• Evidence in BTK interventions
• Съображения за разходите
• Current controversies

Stenting Considerations

Limited but evolving role:

• Bailout stenting indications:
• Flow-limiting dissection
• Elastic recoil
• Residual stenosis >30%
• Abrupt closure

• Perforation management

• Stent platforms:

• Bare metal stents
• Drug-eluting stents
• Self-expanding vs. balloon-expandable
• Dedicated BTK designs

• Sizing considerations

• Technical considerations:

• Precise placement
• Avoidance of joint spaces
• Coverage of dissection entry/exit points
• Minimal overlap
• Preservation of collaterals

Atherectomy in BTK Interventions

Debulking heavily calcified vessels:

• Device options:
• Orbital atherectomy
• Rotational atherectomy
• Directional atherectomy
• Laser atherectomy

• Mechanism-specific applications

• Technical considerations:

• Vessel sizing
• Run length
• Embolization protection
• Adjunctive therapy

• Calcium burden assessment

• Evidence base:

• Limited randomized data
• Observational studies
• Съображения за разходите
• Learning curve
• Complication management

Specialized Technologies

Addressing specific challenges:

• Chronic total occlusion devices:
• Dedicated crossing wires
• Support catheters
• Re-entry tools
• Specialty devices

• Technique optimization

• Calcium modification:

• Lithoplasty
• Specialized atherectomy
• High-pressure balloons
• Scoring/cutting technologies
• Preparation for definitive therapy

Клинични резултати и доказателствена база

Technical Success Metrics

Defining procedural achievement:

• Angiographic endpoints:
• <30% residual stenosis
• Absence of flow-limiting dissection
• Straight-line flow to foot
• Improved perfusion

• Target lesion patency

• Hemodynamic improvement:

• Pulse restoration
• ABI improvement (limited utility)
• Toe pressure increase
• TcPO2 improvement

• Skin perfusion pressure increase

• Технически успехи:

• 80-95% in contemporary series
• Lower with calcification
• Reduced in long occlusions
• Operator experience dependent
• Technology-specific variations

Клинични резултати

Patient-centered results:

• Wound healing:
• 60-80% at 1 year
• Time to healing (typically 3-6 months)
• Factors affecting healing
• Recurrence rates

• Need for adjunctive therapies

• Limb salvage:

• 80-90% at 1 year
• Factors predicting failure
• Level of amputation when necessary
• Functional outcomes

• Въздействие върху качеството на живот

• Patency rates:

• Primary patency 40-60% at 1 year
• Secondary patency 60-80% at 1 year
• Restenosis patterns
• Reintervention frequency
• Surveillance protocols

Доказателствена база

Current data on BTK interventions:

• Key clinical trials:
• BASIL trial (limited BTK-specific data)
• DEBATE-BTK (drug-coated balloons)
• IN.PACT DEEP (cautionary DCB results)
• ACHILLES (sirolimus stents)

• YUKON-BTK (drug-eluting stents)

• Meta-analyses findings:

• Heterogeneous results
• Limited high-quality evidence
• Technology-specific outcomes
• Patient selection importance

• Need for standardized reporting

• Guidelines recommendations:

• Endovascular-first approach for most CLI
• Consideration of patient factors
• Individualized decision-making
• Multidisciplinary team involvement
• Recognition of evidence limitations

Усложнения и управление

Procedural Complications

Recognition and management:

• Access site complications:
• Hematoma
• Pseudoaneurysm
• Arteriovenous fistula
• Vessel occlusion

• Management approaches

• Vessel-related complications:

• Dissection (management strategies)
• Perforation (balloon tamponade, covered stents)
• Embolization (aspiration, thrombolysis)
• Acute thrombosis (thrombolytics, reopening)

• Vasospasm (vasodilators)

• Systemic complications:

• Contrast nephropathy
• Radiation exposure
• Allergic reactions
• Cardiovascular events
• Стратегии за превенция

Post-Procedural Management

Optimizing outcomes:

• Pharmacotherapy:
• Antiplatelet regimens
• Statin therapy
• Antithrombotic considerations
• Duration of dual antiplatelet therapy

• Risk factor modification

• Wound care coordination:

• Multidisciplinary approach
• Offloading strategies
• Infection management
• Advanced wound therapies

• Follow-up protocols

• Surveillance protocols:

• Clinical assessment frequency
• Non-invasive testing approaches
• Duplex ultrasound criteria
• Intervention triggers
• Long-term monitoring

Special Considerations and Future Directions

Diabetic Patients

Unique challenges in diabetes:

• Disease pattern differences:
• Predilection for tibial vessels
• Heavy calcification
• Diffuse disease
• Микроваскуларна дисфункция

• Impaired collateralization

• Technical adaptations:

• Calcium modification strategies
• Consideration of pedal arch
• Angiosome-directed approaches
• Aggressive debulking

• Specialized crossing techniques

• Outcome considerations:

• Wound healing primary goal
• Integration with diabetic foot care
• Infection management
• Reintervention frequency
• Amputation prevention focus

End-Stage Renal Disease

Challenging comorbidity:

• Specific challenges:
• Extensive calcification
• Poor wound healing
• Increased infection risk
• Contrast considerations

• Accelerated restenosis

• Management adaptations:

• CO2 angiography
• Careful contrast management
• Timing relative to dialysis
• Infection prevention emphasis
• Modified expectations

Emerging Technologies

Future directions:

• Drug delivery innovations:
• Next-generation drug-coated balloons
• Novel drug-eluting stents
• Bioresorbable scaffolds
• Targeted delivery systems

• Комбинирани подходи

• Dedicated BTK devices:

• Purpose-designed stent platforms
• Low-profile delivery systems
• Specialized crossing tools
• Calcium modification technologies

• Embolic protection

• Biological approaches:

• Cell-based therapies
• Приложения на растежни фактори
• Gene therapy
• Combined approaches
• Wound healing acceleration

Медицинска декларация за отказ от отговорност

Важно известие: This information is provided for educational purposes only and does not constitute medical advice. Below-the-knee interventions for peripheral arterial disease represent specialized procedures that should only be performed by qualified healthcare professionals with appropriate training and expertise in endovascular techniques. The approaches discussed should only be implemented under appropriate medical supervision. Individual treatment decisions should be based on patient-specific factors, current clinical guidelines, and physician judgment. If you have been diagnosed with peripheral arterial disease or are experiencing symptoms such as leg pain, non-healing wounds, or discoloration of the feet, please consult with a healthcare professional for proper evaluation and treatment recommendations. This article is not a substitute for professional medical advice, diagnosis, or treatment.

Заключение

Below-the-knee interventions represent a technically challenging but increasingly important component of the endovascular treatment armamentarium for peripheral arterial disease, particularly in the setting of critical limb ischemia. Despite the anatomical and technical challenges posed by small vessel diameter, diffuse disease, and heavy calcification, contemporary approaches and evolving technologies have expanded treatment options for patients who previously faced limited alternatives. While the primary goal of these interventions remains limb salvage rather than long-term patency, ongoing technological innovations continue to improve both technical success and clinical outcomes. A multidisciplinary approach integrating endovascular specialists, wound care experts, podiatrists, and other healthcare professionals offers the best opportunity for successful limb salvage and improved quality of life for patients with infrapopliteal arterial disease.