High Yield Overview

CHOPART AMPUTATION (TRANSVERSE TARSAL AMPUTATION)

Plantar-based flap - racquet incision with long plantar flap and short dorsal flap | advanced

Critical Danger Structures - 5 Key Zones

Danger Zone 1: Dorsalis Pedis Artery

Location: Runs between EHL and EDL tendons at ankle level, 2-3cm distal to talonavicular joint on dorsal midfoot

Protection Strategy: Early identification after dorsal skin incision, careful retraction during tendon division, preserve adventitia, avoid electrocautery within 5mm, maintain visualization throughout dorsal dissection

Danger Zone 2: Medial Plantar Neurovascular Bundle

Location: Branches from posterior tibial artery/nerve 1cm distal to medial malleolus, runs 15-20mm from medial plantar border, primary supply to plantar flap

Protection Strategy: Dissect superficial to neurovascular plane during medial approach, preserve all plantar soft tissue thickness, identify and protect before TP tendon division, maintain flap perfusion checks

Danger Zone 3: Lateral Plantar Neurovascular Bundle

Location: Accompanies lateral plantar nerve lateral to FDL, gives calcaneal branches for heel sensation, runs deep to plantar aponeurosis

Protection Strategy: Lateral dissection stays superficial to deep fascia, protect during peroneal tendon division, preserve calcaneal branches, maintain lateral flap thickness

Danger Zone 4: Talar Articular Cartilage

Location: Talar head (talonavicular joint) and anterior/middle facets of talus, will become exposed weight-bearing surface if arthrodesis not performed

Protection Strategy: Careful capsular dissection to avoid gouging cartilage, smooth bone edges only (do not violate subchondral bone if preserving joint), consider arthrodesis to prevent arthrosis

Danger Zone 5: Deep Peroneal Nerve

Location: Runs with dorsalis pedis artery between EHL and EDL, provides sensation to 1st web space, motor to EDB

Protection Strategy: Identify with dorsalis pedis artery, gentle retraction only, avoid traction injury during joint exposure, divide sharply if necessary (motor loss acceptable, sensory loss problematic)

Mnemonic

CHOPART

Mnemonic

EQUINUS

Indications

Absolute Indications:

Severe irreparable forefoot trauma with viable hindfoot
Diabetic forefoot gangrene/osteomyelitis with intact hindfoot perfusion
Malignant tumor of forefoot requiring negative margins
Failed multiple ray amputations with non-functional forefoot remnant
Chronic forefoot osteomyelitis unresponsive to medical/surgical management

Relative Indications:

Severe Charcot forefoot deformity with irreparable midfoot collapse
Congenital forefoot deformity requiring reconstruction
Extensive soft tissue loss of forefoot with exposed bone
Peripheral vascular disease (PVD) when more distal amputation inadequate

Contraindications:

Inadequate perfusion (TCPO2 less than 30mmHg, ABI less than 0.5)
Active hindfoot infection/osteomyelitis
Ischemic heel or Achilles region
Severe PVD requiring higher-level amputation
Patient non-ambulatory (consider BKA for prosthetic fitting)
Psychiatric/cognitive inability to cooperate with rehabilitation

Evidence Base

Australian Context

PBS: No specific listings for Chopart amputation medications
Medicare MBS: Item 50312 (midtarsal amputation) - complex procedure requiring detailed documentation
eTG Antibiotic Guidelines: Prophylaxis - cephazolin 2g IV pre-incision (or vancomycin if MRSA risk); therapeutic for diabetic infection - piperacillin-tazobactam 4.5g IV q8h
AOANJRR: Not applicable (arthroplasty registry)
Australian epidemiology: Diabetic foot complications account for 60% of Chopart amputations, increasing Indigenous population burden

Step 1: Vascular Assessment & Planning

CRITICAL first step - determines amputation feasibility:

Palpate dorsalis pedis and posterior tibial pulses
Measure TCPO2 (transcutaneous oxygen pressure): MUST be greater than 30mmHg for healing
Calculate ankle-brachial index (ABI): MUST be greater than 0.5
Assess skin quality, capillary refill, temperature
If marginal perfusion: consider vascular surgery consultation for revascularization first

Plan flap dimensions:

Plantar flap must extend to distal forefoot (metatarsal head level) for adequate length
Measure distance from planned transverse tarsal cut to dorsum - flap must reach without tension
Mark talonavicular and calcaneocuboid joint positions (fluoroscopy helpful)

Exam Pearl

Exam Key: "Chopart preserves the ankle joint and talus/calcaneus. Before proceeding, I MUST confirm adequate perfusion - palpable pulses, TCPO2 greater than 30mmHg, and ABI greater than 0.5. Inadequate perfusion is a contraindication requiring higher-level amputation. I plan a long plantar flap extending to the distal forefoot to ensure tension-free dorsal coverage."

Critical Dangers

Inadequate vascular assessment leads to flap failure and revision to higher level
Short plantar flap causes tension, necrosis, and wound breakdown
Wrong level selection (should consider Syme's/BKA if perfusion marginal)

Step 2: Positioning, Preparation, and Flap Marking

Patient Positioning:

Supine with ipsilateral hip bump (30 degrees internal rotation)
Thigh tourniquet applied (inflate to 250-300mmHg for lower extremity)
Affected foot off end of table or on radiolucent support
Prep from tourniquet to toes

Racquet Incision Marking:

Transverse dorsal limb: Across talonavicular and calcaneocuboid joints (palpate, fluoroscopy confirm)
Medial extension: Curve distally along medial midfoot to plantar surface
Lateral extension: Curve distally along lateral midfoot to plantar surface
Plantar limb: Transverse or gently curved incision at distal forefoot/metatarsal head level
Plantar flap is LONG (6-8cm from transverse tarsal joint), dorsal flap is SHORT (1-2cm)

Exam Pearl

Exam Key: "I use a 'racquet incision' with a long plantar flap and short dorsal flap. The plantar skin is sensate, thick, and durable - ideal for the weight-bearing surface. The flap must extend far enough distally to reach the dorsum without any tension."

Critical Dangers

Short plantar flap is the most common technical error causing flap tension and necrosis
Incision too proximal risks injury to medial/lateral plantar neurovascular bundles
Incision too distal wastes viable forefoot tissue

Step 3: Dorsal Dissection and Neurovascular Identification

Incise dorsal skin and subcutaneous tissue:

Sharply incise along marked transverse dorsal incision
Deepen through subcutaneous fat to extensor retinaculum

Identify and protect dorsalis pedis artery:

Runs between EHL (medial) and EDL (lateral) tendons
Palpate pulsations, visualize artery and accompanying deep peroneal nerve
CRITICAL: This vessel supplies dorsal skin - injury causes skin necrosis

Divide extensor tendons:

Identify TA (most medial), EHL, EDL, peroneus tertius (if present)
Tag tendons with sutures for later use (can anchor to talus to prevent equinus)
Divide tendons sharply under direct vision
Retract proximally to expose talonavicular and calcaneocuboid joint capsules

Exam Pearl

Exam Key: "I identify the dorsalis pedis artery running between EHL and EDL tendons. I protect this vessel meticulously as it supplies the dorsal skin. I tag the extensor tendons with sutures - these can be anchored to the talar neck later to provide dorsiflexion force and help prevent equinus deformity."

Critical Dangers

Dorsalis pedis injury causes dorsal skin ischemia and wound breakdown
Deep peroneal nerve traction injury (usually not critical as motor loss to EDB only)
Inadequate joint capsule exposure leads to difficulty with disarticulation

Step 4: Medial Dissection and Plantar Nerve Preservation

Extend medial limb of incision:

Curve distally along medial border of foot
Deepen through skin and subcutaneous tissue

Identify tibialis posterior tendon:

Large tendon inserting on navicular tuberosity (medial midfoot prominence)
Palpate, visualize insertion
Divide tendon sharply but DO NOT retract immediately

CRITICAL: Identify and protect medial plantar neurovascular bundle:

Runs 15-20mm from medial plantar border, deep to skin/fat but superficial to flexor tendons
Branches from posterior tibial artery/nerve 1cm distal to medial malleolus
PRIMARY blood supply to plantar flap
PRIMARY sensation to weight-bearing surface
Dissect superficial to this bundle, preserve within plantar flap thickness

Exam Pearl

Exam Key: "The medial plantar neurovascular bundle is CRITICAL to the success of this operation. It provides the blood supply and protective sensation to the plantar flap. I dissect carefully, staying superficial to this bundle and preserving it within the full thickness of the plantar flap. Injury here is catastrophic - the stump becomes insensate and prone to ulceration."

Critical Dangers

Medial plantar nerve injury creates insensate stump (major functional failure)
Medial plantar artery injury causes flap ischemia and necrosis
Inadvertent TP tendon avulsion from navicular causes bleeding

Step 5: Lateral Dissection and Sural Nerve Protection

Extend lateral limb of incision:

Curve distally along lateral border of foot
Deepen through skin and subcutaneous tissue

Identify peroneal tendons:

Peroneus brevis: Inserts on 5th metatarsal base (palpate)
Peroneus longus: Crosses plantar to 1st cuneiform
Divide both tendons sharply

Protect sural nerve:

Runs along lateral border of foot, supplies lateral foot sensation
Identify and protect or divide sharply under direct vision (if necessary)

Identify lateral plantar neurovascular bundle:

Accompanies lateral plantar nerve
Gives calcaneal branches supplying heel sensation
Preserve within plantar flap

Exam Pearl

Exam Key: "I protect the sural nerve laterally to preserve lateral foot sensation, though this is less critical than plantar nerves. The lateral plantar neurovascular bundle is preserved within the plantar flap. The calcaneal branches from this bundle provide heel sensation."

Critical Dangers

Sural nerve injury causes lateral foot numbness (usually well-tolerated)
Lateral plantar nerve injury reduces plantar sensation
Peroneal artery injury (if present) can compromise lateral flap perfusion

Step 6: Joint Capsule Opening and Disarticulation

Expose transverse tarsal joint:

Identify talonavicular joint capsule medially
Identify calcaneocuboid joint capsule laterally
These two joints together form the transverse tarsal (Chopart) joint

Open joint capsules:

Sharply incise talonavicular capsule circumferentially
Sharply incise calcaneocuboid capsule circumferentially
Plantarflex foot to open joints

Disarticulate forefoot:

Carefully disarticulate navicular from talar head
Disarticulate cuboid from calcaneus
Remove navicular, cuboid, and entire forefoot en bloc
PRESERVE talus and calcaneus articular surfaces (avoid gouging cartilage)

Exam Pearl

Exam Key: "Chopart amputation is a true disarticulation through the transverse tarsal joint - the talonavicular joint medially and calcaneocuboid joint laterally. I carefully preserve the articular cartilage of the talus and calcaneus. These surfaces can be preserved for motion or prepared for arthrodesis depending on my equinus prevention strategy."

Critical Dangers

Damage to talar head cartilage causes arthritis if joint preserved
Calcaneal articular surface damage complicates arthrodesis if planned
Incomplete bone removal leaves sharp prominences causing ulceration

Step 7: Plantar Flap Development

Develop full-thickness plantar flap:

Incise plantar skin at marked distal level (metatarsal heads)
Include ALL plantar structures in flap:
- Skin
- Subcutaneous fat
- Plantar aponeurosis
- Medial and lateral plantar neurovascular bundles (CRITICAL)
Divide FHL and FDL tendons distally (preserve proximal stumps)

Assess flap perfusion:

Release tourniquet briefly to assess flap bleeding
Ensure brisk capillary refill
Doppler medial and lateral plantar arteries to confirm flow

Trim excess tissue:

Remove excess fat to allow flap to lie flat without bulk
DO NOT thin the flap excessively - maintain vascular plexus and nerve protection

Exam Pearl

Exam Key: "The plantar flap contains sensate plantar skin with intact medial and lateral plantar nerves for protective sensation. I preserve the full thickness of the flap including the plantar fat and aponeurosis for durable padding. The flap must be long enough to reach the dorsum without any tension - tension is the main cause of flap failure."

Critical Dangers

Thin flap lacks padding and is prone to ulceration
Nerve injury during flap development creates insensate stump
Vascular injury causes flap necrosis
Short flap creates tension leading to ischemia and dehiscence

Step 8: Equinus Prevention - Achilles Lengthening

CRITICAL STEP - addresses the major complication of Chopart:

Equinus deformity occurs in 30-50% due to Achilles overpull after loss of dorsiflexors. MUST address at index surgery.

Option 1A: Achilles Z-plasty Lengthening (Preferred by many):

Make 3cm longitudinal incision over Achilles (posteromedial)
Perform Z-plasty: proximal medial hemisection, distal lateral hemisection, 3-4cm apart
Dorsiflex foot to neutral, sutures ends with knee flexed (reduces tension)
Risk: Over-lengthening causes calcaneus gait

Option 1B: Percutaneous Triple Hemisection:

Three 1cm stab incisions over Achilles
Proximal medial, middle lateral, distal medial hemisections
Dorsiflex to neutral, allow healing with lengthening

Examiner will ask: "How much lengthening?"

Lengthen until foot rests at NEUTRAL (90 degrees) with knee extended
Typically requires 2-3cm of lengthening
Check with foot held in dorsiflexion - should have no resistance

Exam Pearl

Exam Key: "The MAJOR complication of Chopart amputation is equinus deformity, occurring in 30-50% of cases. This happens because the Achilles tendon overpowers the lost dorsiflexors. I address this at the index surgery with Achilles lengthening - either Z-plasty or percutaneous triple hemisection. I lengthen until the foot rests at neutral with no resistance to dorsiflexion."

Critical Dangers

Failure to address equinus leads to progressive plantarflexion contracture
Over-lengthening causes calcaneus gait and weak push-off
Under-lengthening fails to prevent equinus development

Step 9: Equinus Prevention - Tendon Transfer (Optional)

Alternative/adjunct to Achilles lengthening:

Anchor extensor tendons to talus:

Use tagged TA, EDL, and EHL tendons (from Step 3)
Drill holes in talar neck (dorsal to articular surface)
Pass tendons through drill holes or anchor with suture anchors
Suture tendons under tension with foot at neutral
Provides active dorsiflexion force to balance Achilles

Advantages:

Maintains some active dorsiflexion
Theoretically better balance than lengthening alone

Disadvantages:

Technically demanding
Limited evidence of effectiveness
Tendons may stretch over time

Exam Pearl

Exam Key: "Some surgeons anchor the extensor tendons to the talar neck to provide a dorsiflexion force balancing the Achilles. I drill holes in the talar neck and pass the TA, EDL, and EHL through, then suture them under tension with the foot at neutral. Evidence is limited, but theoretically this provides better muscle balance."

Critical Dangers

Drill hole through talar articular cartilage causes arthritis
Excessive tension on transfer causes necrosis
Tendon pullout if fixation inadequate

Step 10: Equinus Prevention - Talocalcaneal Arthrodesis (Optional)

Most definitive equinus prevention - increasingly popular:

Technique:

Debride talar and calcaneal articular cartilage at subtalar joint
Denude to bleeding subchondral bone
Position talus and calcaneus at neutral alignment (hindfoot valgus 5 degrees)
Fix with 1-2 cannulated screws (typically 6.5-7.3mm) from calcaneus into talus
Bone graft from resected navicular/cuboid

Advantages:

Creates stable, rigid platform
PREVENTS equinus deformity most reliably
Eliminates subtalar motion (already limited in Chopart patients)

Disadvantages:

Increases surgery time (30-45 minutes)
Nonunion risk 10-15%
Requires protected weight-bearing longer (10-12 weeks)

Exam Pearl

Exam Key: "Many surgeons now perform talocalcaneal arthrodesis at the time of Chopart amputation. This creates a stable platform and prevents equinus deformity most reliably. I debride the subtalar joint to bleeding bone, position the hindfoot in 5 degrees valgus and neutral dorsiflexion, and fix with cannulated screws. The nonunion risk is 10-15%, but the equinus prevention is superior."

Critical Dangers

Malposition (varus or excess valgus) causes abnormal weight-bearing
Nonunion requires revision surgery
Screw penetration into ankle joint

Step 11: Bone Contouring

Smooth all bone surfaces:

Use rongeur to smooth talar head and calcaneal cuboid surface
Remove any sharp edges or prominences
Create smooth contour that allows flap to lie flat
If arthrodesis NOT performed: preserve articular cartilage but smooth edges
If arthrodesis performed: ensure adequate bone opposition

Check flap fit:

Bring plantar flap dorsally
Ensure flap lies flat over bone without tension
No bony prominences palpable through flap

Exam Pearl

Exam Key: "I carefully smooth all bone surfaces with a rongeur. Any bony prominence will cause pressure ulceration through the flap. If preserving the joints, I avoid violating subchondral bone. If performing arthrodesis, I ensure adequate bleeding bone surfaces for fusion."

Critical Dangers

Bony prominences cause pressure ulcers
Excessive bone removal weakens structure
Violation of articular cartilage if preserving joints

Step 12: Flap Inset and Anchoring

Position plantar flap:

Release tourniquet and achieve hemostasis (critical - see next step)
Bring plantar flap dorsally over talus and calcaneus
Check for tension - flap MUST lie flat without any pull
If tension present: revise bone further or accept that amputation level too distal

Anchor flap to prevent migration:

Suture plantar aponeurosis to dorsal periosteum with 2-0 absorbable sutures
Anchor to tendon stumps if available
Multiple interrupted sutures distributing load
Goal: Prevent distal migration of flap, maintain sensate plantar skin over weight-bearing surfaces

Exam Pearl

Exam Key: "I anchor the plantar flap to dorsal structures with multiple absorbable sutures. This prevents distal migration over time and ensures the sensate plantar skin remains positioned over the weight-bearing talus and calcaneus. The flap must lie flat without any tension - tension is the number one cause of flap failure."

Critical Dangers

Tension on flap causes ischemia and necrosis (most common cause of failure)
Inadequate anchoring allows flap to migrate, exposing bone dorsally
Sutures through neurovascular bundles cause injury

Step 13: Meticulous Hemostasis and Drainage

CRITICAL STEP - hematoma compromises flap perfusion:

Release tourniquet:

Deflate tourniquet completely
Allow 10 minutes for normal blood pressure to re-establish
Identify ALL bleeding vessels

Achieve hemostasis:

Bipolar electrocautery for small vessels
Suture ligate larger vessels (avoid electrocautery near nerves)
Do NOT close until bone-dry hemostasis achieved
Hematoma is a major cause of flap failure

Place drain:

Deep drain beneath flap
Exit lateral or medial to incision (NOT through flap)
Remove at 24-48 hours

Exam Pearl

Exam Key: "I achieve meticulous hemostasis with the tourniquet deflated. Hematoma beneath the flap compromises perfusion and increases infection risk. I use bipolar cautery carefully, avoiding the plantar nerves. I place a deep drain to prevent fluid accumulation, exiting away from the neurovascular bundles."

Critical Dangers

Hematoma causes flap ischemia and infection
Electrocautery near plantar nerves causes nerve injury
Drain through neurovascular bundle causes injury

Step 14: Layered Closure

Deep layer:

Approximate subcutaneous tissue with 3-0 absorbable sutures
Reduce dead space
NO tension on skin edges

Skin closure:

Interrupted nylon or staples
Approximate plantar flap edge to dorsal skin edge
Ensure good flap contact with underlying bone
Leave 1-2mm gaps between sutures if edema present (can tighten in dressing)

Dressing:

Non-adherent gauze over incision
Fluffed gauze padding over entire stump
Soft roll and elastic wrap (loose - no circumferential constriction)
Posterior splint from toes to knee

CRITICAL: Splint position:

Foot at NEUTRAL (90 degrees)
NEVER plantarflexion (encourages equinus)
Knee at 30 degrees flexion (reduces Achilles tension)

Exam Pearl

Exam Key: "I close in layers without any tension. The key is that the plantar flap must reach the dorsum easily - if there's tension, the amputation level is wrong. I apply a bulky padded dressing and posterior splint with the foot at NEUTRAL position. Splinting in plantarflexion encourages equinus contracture."

Critical Dangers

Tension on closure causes dehiscence and flap necrosis
Splint in plantarflexion causes equinus contracture
Tight circumferential dressing causes compartment syndrome

Post-operative Protocol

Immediate (0-2 weeks):

Hospital stay: 3-5 days (longer if diabetic, infection)
Dressing: Bulky padded dressing, posterior splint foot at neutral
Weight-bearing: NON-weight bearing, strict bedrest day 1
Drain: Remove at 24-48 hours when output less than 30mL per 24hrs
Analgesia: PCA or epidural days 1-2, then oral (paracetamol, oxycodone, gabapentin for neuropathic)
DVT prophylaxis: Enoxaparin 40mg SC daily (mechanical if high bleeding risk)
Glycemic control: Target glucose 6-10 mmol/L in diabetics
Dressing change: First change at 48-72 hours, assess flap perfusion

Early (2-6 weeks):

Wound care: Dressing changes every 2-3 days, monitor flap viability
Splinting: Posterior splint in neutral, change weekly to assess for equinus
Weight-bearing: Non-weight bearing, walker/crutches
Suture removal: 3-4 weeks (longer if diabetic, delayed healing)
Serial casting: If equinus developing, weekly casts to maintain neutral
Physiotherapy: Upper body strengthening, transfer training, contralateral leg strengthening

Intermediate (6-12 weeks):

AFO fitting: Custom AFO to maintain neutral position, usually required long-term
Weight-bearing progression: Gradual progressive weight-bearing 6-8 weeks if wound healed
Bone healing: If arthrodesis performed, confirm union on X-ray (10-12 weeks)
Prosthetic consultation: Evaluate for prosthetic filler or custom prosthesis
Gait training: Physical therapy for gait with AFO/prosthesis

Long-term (3+ months):

Prosthetic fitting: Custom shoe filler with carbon fiber plate, or custom prosthesis
AFO: 80% require long-term AFO for stability
Follow-up: 3-monthly first year, then 6-monthly
Monitor for: Equinus development, skin breakdown, ulceration
Revision rate: 20-40% require revision to higher level by 5 years

Red Flags Requiring Urgent Review:

Flap discoloration (dusky, blue, black) - vascular compromise
Wound dehiscence with bone exposure
Fever, systemic signs of infection
Progressive equinus deformity
Pressure ulceration
Uncontrolled pain

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 58-year-old diabetic man presents with forefoot gangrene extending to the midfoot. You are considering Chopart amputation. What is your preoperative assessment and what would make you choose a higher level of amputation instead?"

EXCEPTIONAL ANSWER

I would perform a comprehensive vascular assessment to determine amputation level. First, I palpate pulses - dorsalis pedis and posterior tibial. I measure transcutaneous oxygen pressure (TCPO2) at the proposed amputation level - I need TCPO2 greater than 30mmHg for healing, ideally greater than 40mmHg. I calculate ankle-brachial index (ABI) - require ABI greater than 0.5. I assess skin quality, temperature, and capillary refill. If these are adequate and infection is confined to forefoot with viable hindfoot skin, Chopart is feasible. However, I would choose a higher level (Syme's or BKA) if: TCPO2 less than 30mmHg, ABI less than 0.5, hindfoot skin compromise, heel ischemia or infection, patient non-ambulatory (BKA has better prosthetic outcomes), or patient unable to cooperate with prolonged rehabilitation. Given Chopart's high complication rate (60-80%), I have a low threshold to proceed to Syme's or BKA for better functional outcomes.

VIVA SCENARIOStandard

EXAMINER

"What is the major complication of Chopart amputation and how do you prevent it? Walk me through your prevention strategies at the index surgery."

EXCEPTIONAL ANSWER

Equinus deformity is the most common major complication, occurring in 30-50% of cases. It results from muscle imbalance - the Achilles tendon overpowers the lost dorsiflexor muscles (TA, EHL, EDL) and intrinsic foot muscles that are removed with the forefoot. This causes progressive plantarflexion contracture making prosthetic fitting difficult and causing dorsal skin breakdown. I prevent this with multiple strategies at the index surgery. First, I perform Achilles lengthening - either Z-plasty (longitudinal incision, proximal medial and distal lateral hemisections 3-4cm apart) or percutaneous triple hemisection. I lengthen until the foot rests at neutral (90 degrees) with the knee extended, typically requiring 2-3cm of lengthening. Second, I consider anchoring the extensor tendons (TA, EDL, EHL) to the talar neck through drill holes or suture anchors - this provides active dorsiflexion force to balance the Achilles. Third, many surgeons now perform talocalcaneal arthrodesis at the time of Chopart - this creates a stable platform and prevents equinus most reliably, though it adds surgery time and has 10-15% nonunion risk. Postoperatively, I splint in neutral position (NEVER plantarflexion), use serial casting if needed, and fit early AFO. Despite these measures, 30-50% still develop some degree of equinus, and 20-40% require revision to higher level by 5 years.

VIVA SCENARIOStandard

EXAMINER

"During the plantar flap dissection, what are the critical neurovascular structures you must preserve and why are they so important? Describe their anatomy."

EXCEPTIONAL ANSWER

The medial and lateral plantar neurovascular bundles are absolutely critical to preserve - they provide the blood supply and protective sensation to the plantar flap, which becomes the weight-bearing surface. The medial plantar artery and nerve are most important. The medial plantar artery is the larger terminal branch of the posterior tibial artery, branching 1cm distal to the medial malleolus. It runs 15-20mm from the medial plantar border, deep to skin and subcutaneous fat but superficial to flexor tendons. It provides the primary blood supply to the plantar flap. The medial plantar nerve runs with the artery and provides sensation to the medial plantar skin - this is the primary weight-bearing area. The lateral plantar artery and nerve are the smaller terminal branches, running lateral to FDL and deep to plantar aponeurosis. The lateral plantar nerve gives calcaneal branches that supply heel sensation. During dissection, I must stay superficial to these bundles, preserving them within the full thickness of the plantar flap. I dissect the flap with skin, fat, aponeurosis, and neurovascular bundles as a composite unit. Injury to the medial plantar nerve creates an insensate weight-bearing surface - this is catastrophic as the patient cannot feel pressure or trauma, leading to recurrent ulceration. Injury to the plantar arteries causes flap ischemia and necrosis. An insensate or ischemic Chopart stump has very poor function and usually requires revision to higher level.

Chopart Amputation - Exam Quick Reference

High-Yield Exam Summary

References

Pinzur MS, Stuck RM, Sage R, Hunt N, Rabinovich Z. Syme ankle disarticulation in patients with diabetes. J Bone Joint Surg Am. 2003;85(9):1667-1672. doi:10.2106/00004623-200309000-00002
Pinzur MS, Smith D, Osterman H. Syme ankle disarticulation in peripheral vascular disease and diabetic foot infection: the one-stage versus two-stage procedure. Foot Ankle Int. 1995;16(3):124-127. doi:10.1177/107110079501600304
Bowker JH, San Giovanni TP, Pinzur MS. North American experience with knee disarticulation with use of a posterior myofasciocutaneous flap. J Bone Joint Surg Am. 2000;82(11):1571-1574.
Sanders LJ, Dunlap G. Transmetatarsal amputation. A successful approach to limb salvage. J Am Podiatr Med Assoc. 1992;82(3):129-135. doi:10.7547/87507315-82-3-129
Dillon MP, Fatone S. Deliberations about the functional benefits and complications of partial foot amputation: do we know the full story? Med Hypotheses. 2013;81(4):754-761. doi:10.1016/j.mehy.2013.07.037
Wagner FW Jr. Amputations of the foot and ankle. Current status. Clin Orthop Relat Res. 1977;(122):62-69.
Early JS, Hansen ST. Surgical reconstruction of the diabetic foot: a salvage approach for midfoot collapse. Foot Ankle Int. 1996;17(6):325-330. doi:10.1177/107110079601700604
Catanzariti AR, Mendicino R, Haverstock B. Ostectomy for diabetic neuroarthropathy involving the midfoot. J Foot Ankle Surg. 2000;39(5):291-300. doi:10.1016/s1067-2516(00)80047-8
Harris WR. The classic: Syme's amputation: the technical details essential for success by Austen Harris. Clin Orthop Relat Res. 2012;470(4):947-950. doi:10.1007/s11999-011-2195-6
Pinzur MS, Pinto MA, Saltzman M, Batista F, Gottschalk F, Juknelis D. Health-related quality of life in patients with transtibial amputation and reconstruction with bone bridging of the distal tibia and fibula. Foot Ankle Int. 2006;27(11):907-912. doi:10.1177/107110070602701107

Chopart Amputation (Transverse Tarsal Amputation)