AMPUTATION SURGICAL PRINCIPLES
Level Selection | Myodesis vs Myoplasty | Prosthetic Considerations | Multidisciplinary Approach
AMPUTATION INDICATIONS
Critical Must-Knows
- Myodesis = muscle sutured to bone (optimal function), myoplasty = muscle to fascia/muscle
- Bone handling: Round edges, bevel tibia anteriorly, adequate bone length for lever arm
- Nerve management: Identify, transect sharply under tension, allow retraction into soft tissues
- Prosthetic consideration: Preserve joints where possible, adequate soft tissue envelope
- Phantom limb pain affects 70-80% - multifactorial, prevention with perioperative analgesia
Examiner's Pearls
- "Equal anterior-posterior flaps for transfemoral, longer posterior flap for transtibial
- "Maintain knee for BKA - reduces energy expenditure by 40-60% vs AKA
- "Traction neurectomy reduces neuroma pain - pull nerve, transect sharply, allow retraction
- "Staged approach for infection: guillotine then definitive closure when sepsis controlled
Critical Amputation Surgical Exam Points
Level Selection Principles
Preserve maximum functional length while ensuring healing. For vascular disease, balance healing potential (more proximal heals better) against function (more distal preserves joints). Knee preservation is paramount - reduces energy expenditure by 40-60% compared to transfemoral. Always consider prosthetic requirements.
Myodesis vs Myoplasty
Myodesis = muscle attached directly to bone through drill holes or suture anchors. Provides optimal muscle tension and proprioception. Myoplasty = muscle sutured to opposing muscle or fascia. Quicker but less stable. Myodesis is the gold standard for functional amputation - know this distinction.
Nerve and Bone Management
Nerves: Identify major nerves, apply gentle traction, transect sharply with new blade, allow proximal retraction into soft tissues away from scar. Bone: Rasp edges smooth, bevel tibia anteriorly to prevent skin breakdown, adequate length for lever arm and prosthetic socket.
Phantom Limb Pain
Affects 70-80% of amputees. Distinct from residual limb pain. Risk factors: preoperative pain, traumatic amputation. Prevention: perioperative epidural/nerve blocks. Treatment is multimodal - mirror therapy, gabapentinoids, antidepressants, TENS. Counsel patients preoperatively.
Amputation Level Selection Guide
| Indication | Preferred Level | Key Principle | Prosthetic Consideration |
|---|---|---|---|
| Diabetic foot with gangrene | Transmetatarsal or transtibial | Preserve knee if vascular supply adequate | Short BKA still better than AKA |
| Critical limb ischaemia, failed revascularization | Transtibial if popliteal pulse, else transfemoral | Level determined by healing potential | Consider vascular input for level selection |
| Trauma with mangled extremity | Most distal viable level | Preserve length, consider reconstruction first | MESS score greater than 7 indicates amputation |
| Osteosarcoma distal femur | Transfemoral with wide margin | Oncological margin takes priority (greater than 2cm) | Consider skip metastases, rotationplasty alternative |
| Necrotizing fasciitis | Guillotine at viable level | Life before limb - emergent debridement | Revise to definitive level when sepsis controlled |
VICTIMAmputation Indications
Memory Hook:The limb became a VICTIM of disease requiring amputation
FLAPSTranstibial Amputation Technique
Memory Hook:Good FLAPS make a good stump - posterior flap is key for BKA
MIRRORSPhantom Limb Pain Management
Memory Hook:Use MIRRORS to treat phantom pain - mirror therapy is evidence-based
Overview and Epidemiology
Amputation is the surgical removal of part or all of a limb. While historically considered a failure of treatment, modern amputation surgery is a reconstructive procedure aiming to create a functional residual limb optimized for prosthetic fitting and rehabilitation.
Epidemiology:
- Lower limb amputations are 10-20 times more common than upper limb
- Vascular disease (peripheral vascular disease, diabetes) accounts for approximately 80% of major amputations
- Incidence increases with age - 65% occur in patients over 65 years
- Diabetes increases amputation risk 15-40 fold
- Male predominance (2:1 ratio)
Modern Amputation Philosophy
Amputation is reconstruction, not failure. The goal is to create a residual limb that maximizes function and quality of life. This requires attention to bone length, soft tissue envelope, muscle stabilization, and prosthetic considerations. A well-performed amputation with good rehabilitation can provide excellent functional outcomes.
Indications - The VICTIM Mnemonic:
Vascular Disease (80%)
- Peripheral vascular disease: Critical limb ischaemia, gangrene
- Diabetic foot disease: Infection, osteomyelitis, Charcot collapse
- Failed revascularization
- Unsalvageable tissue loss
Trauma and Tumour
- Trauma: Mangled extremity, irreconstructible injury (MESS greater than 7)
- Malignancy: Where limb salvage not possible, skip metastases
- Palliative amputation for fungating tumours
- Failed limb salvage with recurrence
Contraindications (Relative):
- Inadequate healing potential (assess with vascular studies)
- Unrealistic patient expectations
- Inability to participate in rehabilitation
- Life expectancy precluding benefit from rehabilitation
Pathophysiology and Wound Healing
Factors Affecting Wound Healing
Understanding the pathophysiology of wound healing is crucial for successful amputation surgery, particularly in the vascular population.
Factors Affecting Amputation Healing
| Factor | Effect on Healing | Clinical Implication |
|---|---|---|
| Peripheral vascular disease | Reduced tissue perfusion, impaired oxygen delivery | Consider vascular input, may need more proximal level |
| Diabetes mellitus | Microangiopathy, neuropathy, impaired immunity | Optimize HbA1c less than 8%, aggressive infection control |
| Smoking | Vasoconstriction, impaired wound healing | Cessation essential - increases healing by 30% |
| Malnutrition | Albumin less than 30 g/L impairs healing | Nutritional optimization preoperatively |
| Renal failure | Uraemia impairs healing, calciphylaxis risk | Dialysis optimization, higher complication rates |
Vascular Assessment
Clinical Assessment:
- Palpable pulses: Femoral, popliteal, posterior tibial, dorsalis pedis
- Tissue perfusion: Skin temperature, capillary refill, tissue viability
- Ankle-brachial index (ABI): Less than 0.4 suggests poor healing potential
- Toe pressures: Greater than 30 mmHg associated with healing
Investigations:
- Doppler arterial studies
- Angiography (CT or conventional) if revascularization considered
- Transcutaneous oxygen tension (TcPO2): Greater than 30-40 mmHg predicts healing
Level Selection in Vascular Disease
The most distal level that will heal should be chosen. However, a failed distal amputation requiring revision is worse than a primary proximal amputation. Vascular surgery input is essential - consider revascularization to enable more distal amputation. TcPO2 greater than 30-40 mmHg at proposed level predicts healing.
Phantom Limb Phenomena
Phantom Limb Sensation:
- Non-painful awareness of amputated limb
- Universal after amputation
- Usually diminishes over time
Phantom Limb Pain (PLP):
- Painful sensations perceived in the amputated limb
- Affects 70-80% of amputees
- Can be immediate or delayed onset
- Character: burning, cramping, shooting, stabbing
Pathophysiology of Phantom Pain:
- Peripheral mechanisms: Neuroma formation, ectopic discharge
- Spinal cord changes: Dorsal horn sensitization
- Cortical reorganization: Somatosensory cortex remapping
- Central sensitization: Altered pain processing
Preoperative Pain is Risk Factor
Patients with significant preoperative pain have higher rates of phantom limb pain. This supports the hypothesis that central sensitization occurs before amputation. Perioperative epidural or peripheral nerve blocks may reduce phantom pain incidence.
Clinical Presentation and Assessment
Indications by Aetiology
Vascular Disease and Diabetes
Indications:
- Critical limb ischaemia with rest pain
- Gangrene (dry or wet)
- Non-healing ulcers despite revascularization
- Failed bypass or angioplasty
- Extensive tissue loss precluding reconstruction
Assessment:
- Vascular surgery consultation
- Consider revascularization to enable more distal amputation
- Optimize medical comorbidities (diabetes, cardiac disease)
- Nutritional assessment
Level Selection:
- TcPO2 greater than 30-40 mmHg predicts healing
- Palpable pulse at level above amputation favourable
- When in doubt, vascular opinion essential
Preoperative Assessment Checklist
Medical Optimization
- Vascular assessment: ABI, toe pressures, TcPO2
- Cardiac optimization: Functional status, echo if indicated
- Diabetes control: HbA1c target less than 8%
- Nutrition: Albumin greater than 30 g/L
- Smoking cessation: Refer to Quitline
Multidisciplinary Planning
- Prosthetist: Early involvement for level planning
- Physiotherapy: Preoperative conditioning, wheelchair training
- Occupational therapy: Home assessment, equipment needs
- Psychology: Counselling for body image, grief
- Social work: Discharge planning, support services
Investigations
Investigation Protocol for Amputation Planning
Essential for vascular amputations:
- Ankle-brachial index (ABI): Less than 0.4 suggests poor healing
- Toe pressures: Greater than 30 mmHg associated with healing
- Duplex ultrasound: Assess arterial and venous patency
- CT angiography: If revascularization being considered
- TcPO2: Greater than 30-40 mmHg at proposed level predicts healing
All cases:
- Plain radiographs of affected limb
- Assess bone quality, level of disease
- For trauma: Full trauma series
Oncology:
- MRI whole bone (skip metastases)
- CT chest (staging)
- PET scan if indicated
Preoperative baseline:
- Full blood count, coagulation studies
- Urea, electrolytes, creatinine
- HbA1c (diabetes control)
- Albumin, prealbumin (nutrition)
- CRP, ESR (infection)
- Blood cultures if sepsis suspected
Multidisciplinary team:
- Vascular surgery: Level selection, revascularization options
- Prosthetist: Early involvement for optimal stump planning
- Anaesthesia: Perioperative nerve blocks (phantom pain prevention)
- Pain service: Preoperative pain management plan
TcPO2 for Level Selection
Transcutaneous oxygen tension (TcPO2) is a useful predictor of healing. TcPO2 greater than 40 mmHg has high probability of healing. TcPO2 less than 20 mmHg predicts healing failure. Between 20-40 mmHg is indeterminate - clinical judgment required.
Management Principles
Level Selection Principles
Goals:
- Most distal level that will heal
- Preserve joints where possible (especially knee)
- Adequate bone length for prosthetic lever arm
- Sufficient soft tissue for durable coverage
- Consider prosthetic requirements
Lower Limb Amputation Levels
| Level | Indications | Advantages | Disadvantages |
|---|---|---|---|
| Toe/ray amputation | Localized gangrene, osteomyelitis | Preserves foot function, no prosthesis needed | High revision rate in vascular disease |
| Transmetatarsal | Forefoot gangrene, diabetic foot | Ambulation without prosthesis possible | Equinovarus deformity risk, healing issues |
| Syme (ankle disarticulation) | Ankle pathology, heel pad viable | End-bearing, long lever arm | Cosmesis issues, requires experienced surgeon |
| Transtibial (BKA) | Most common major amputation | Preserves knee - 40-60% less energy vs AKA | Higher revision rate in PVD than AKA |
| Knee disarticulation | Long femoral stump not possible | End-bearing, long lever arm, no bone cut | Bulky prosthetic knee, limited cosmesis |
| Transfemoral (AKA) | Knee preservation not possible | High healing rate (90%+) | Significant energy expenditure increase |
| Hip disarticulation | Proximal thigh tumour, trauma | Complete limb removal | Very high energy expenditure, limited prosthetic use |
Preserve the Knee
Knee preservation is paramount. Energy expenditure for ambulation with transtibial amputation is 40-60% less than transfemoral. Even a short transtibial amputation is preferable to transfemoral if healing is achievable. Vascular input is essential for level decisions.
Surgical Technique
Transtibial (Below-Knee) Amputation
Indications:
- Most common major amputation
- Vascular disease with viable knee
- Trauma with adequate proximal tissue
- Infection controlled at this level
Preoperative Planning:
- Confirm vascularity (clinical, TcPO2)
- Mark level: Minimum 12-15 cm from tibial tuberosity
- Posterior flap length = 1.5 times AP diameter of leg
Transtibial Amputation Steps
Supine position, tourniquet if applicable (avoid in PVD).
Mark level at junction of proximal and middle third of tibia.
Mark anterior fish-mouth incision.
Posterior flap: One-third circumference of leg, extending distally.
Incise skin and deep fascia anteriorly.
Identify and ligate anterior tibial vessels.
Identify deep peroneal nerve - transect sharply under tension.
Divide anterior compartment muscles.
Tibia: Score periosteum, cut with oscillating saw.
Create 45-degree anterior bevel to prevent skin pressure.
Fibula: Cut 1-2 cm shorter than tibia.
Rasp all bone edges smooth.
Create long posterior myocutaneous flap.
Based on gastrocnemius and soleus (soleus often trimmed).
Identify and ligate posterior tibial and peroneal vessels.
Identify tibial and sural nerves - transect sharply under tension.
Drill holes in anterior tibia.
Suture posterior muscle flap to anterior tibia (myodesis).
Close deep fascia over muscle.
Skin closure: Interrupted or subcuticular, no tension.
Apply soft dressing, rigid cast, or IPOP (immediate post-op prosthesis).
Technical Pearls:
- Long posterior flap: Gastrocnemius provides durable, well-vascularized coverage
- Nerve handling: Gentle traction, sharp transection, allow retraction
- Hemostasis: Meticulous - haematoma increases infection risk
- No drain vs drain: Surgeon preference; drain if large dead space
Complications
Wound-Related Complications
Wound Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Wound infection | 10-15% | Diabetes, PVD, malnutrition | Antibiotics, drainage, debridement if needed |
| Wound dehiscence | 5-10% | Tension closure, poor vascularity | VAC therapy, revision if extensive |
| Wound necrosis/failure | 5-20% (higher in PVD) | Inadequate blood supply, wrong level | Debridement, may need more proximal revision |
| Haematoma | 5% | Poor haemostasis, anticoagulation | Aspiration or surgical evacuation |
Revision Amputation:
- Required in 5-30% depending on level and indication
- Higher revision rates with more distal amputations in PVD
- Consider vascular surgery input before revision
Evidence Base and Key Studies
LEAP Study - Limb Salvage vs Amputation in Trauma
- Prospective study comparing limb salvage vs amputation for severe lower extremity trauma
- No significant difference in functional outcomes at 2 years between groups
- Salvage patients had more secondary procedures and complications
- Psychological outcomes similar between groups
- Cost of salvage significantly higher than amputation
Burgess Posterior Myoplasty Technique
- Described long posterior myocutaneous flap for transtibial amputation
- Gastrocnemius provides durable, well-vascularized coverage
- Superior healing rates compared to anterior flaps
- Better prosthetic fitting with muscle-padded stump
- Became the standard technique for BKA
Mirror Therapy for Phantom Limb Pain
- RCT of mirror therapy for phantom limb pain in combat amputees
- Mirror therapy group: 100% reduction in pain at 4 weeks
- Control (covered mirror): No improvement
- Proposed mechanism: Visual feedback resolves cortical conflict
- Simple, no-cost intervention
Perioperative Epidural Analgesia and Phantom Pain
- RCT of perioperative epidural analgesia for amputation
- Epidural group: Lower phantom limb pain at 6 months
- Proposed mechanism: Prevents central sensitization
- Optimized perioperative pain control beneficial
- Combined with multimodal analgesia
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
"A 68-year-old diabetic male presents with wet gangrene of his left foot extending to the mid-foot. He has had a failed femoral-popliteal bypass 6 months ago. His ankle-brachial index is 0.3 and toe pressures are unrecordable. How would you manage this patient?"
"Describe the surgical technique for transtibial amputation, focusing on the key principles that optimize prosthetic function."
"A patient 6 months post-transfemoral amputation complains of severe burning pain in their absent leg. How would you assess and manage this patient?"
Australian Context
Epidemiology in Australia
- Diabetes prevalence increasing - 5.3% of population, higher in Indigenous Australians
- Amputation rates 3 times higher in diabetic vs non-diabetic
- Indigenous Australians have 13 times higher amputation rate
- Peripheral vascular disease remains predominant indication
- Regional variation with higher rates in rural/remote areas
Healthcare Access
- State amputee rehabilitation units in major centers
- PBS-subsidized prosthetics for eligible patients
- Limbs 4 Life support organization (national)
- NDIS funding for prosthetics and rehabilitation
- Telehealth options for remote follow-up
Multidisciplinary Care in Australia:
The Australian model emphasizes multidisciplinary amputation rehabilitation. State amputee rehabilitation units provide comprehensive services including:
- Prosthetist assessment and fitting (often same-day or early)
- Physiotherapy for gait training and strengthening
- Occupational therapy for ADL modification
- Psychology support for adjustment and body image
- Social work for community reintegration
Indigenous Health Considerations:
Indigenous Australians have significantly higher amputation rates due to higher prevalence of diabetes, later presentation, and reduced access to preventive care. Culturally appropriate services, community engagement, and improved access to vascular and podiatric services are priorities. The Close the Gap initiative includes targets for reducing amputation disparities.
Smoking Cessation Resources
Quitline (13 7848) should be offered to all patients preoperatively. Smoking cessation improves wound healing by approximately 30% and is critical for amputation success. Nicotine replacement therapy is PBS-subsidized.
AMPUTATION SURGICAL PRINCIPLES
High-Yield Exam Summary
Indications (VICTIM)
- •Vascular: PVD, diabetes - 80% of amputations
- •Infection: Uncontrolled sepsis, necrotizing fasciitis
- •Congenital: PFFD, fibular hemimelia
- •Trauma: Mangled extremity, MESS greater than 7
- •Ischaemia: Irreversible, failed revascularization
- •Malignancy: Limb salvage not possible
Level Selection
- •Most distal level that will heal
- •Preserve knee - 40-60% less energy vs AKA
- •TcPO2 greater than 30-40 mmHg predicts healing
- •Vascular surgery input essential for PVD
- •Minimum 12-15 cm from tibial tuberosity (BKA)
Technique Principles
- •Myodesis: Muscle to bone (gold standard)
- •Myoplasty: Muscle to muscle/fascia (quicker)
- •Long posterior flap for BKA (Burgess)
- •45-degree anterior tibial bevel
- •Traction neurectomy: Pull, sharp transect, retract
Nerve Management
- •Identify nerve proximally
- •Apply gentle longitudinal traction
- •Transect sharply with fresh blade
- •Allow retraction into soft tissues
- •Position away from scar and pressure
Phantom Limb Pain
- •Affects 70-80% of amputees
- •Risk factor: Preoperative pain
- •First-line: Gabapentinoids
- •Mirror therapy: Strong evidence (NEJM 2007)
- •Prevention: Perioperative regional analgesia
Complications
- •Wound failure: 5-20% (higher in PVD)
- •Revision rate: 5-30% depending on level
- •Contractures: Prevent with early PT
- •Neuroma: Tinel sign, desensitization/injection
- •Depression: 30-50%, early psych support