LOWER LIMB AMPUTATION LEVELS
Level Selection | Energy Expenditure | Prosthetic Outcomes | Surgical Technique by Level
AMPUTATION LEVEL HIERARCHY
Critical Must-Knows
- Energy expenditure increases proximally: Toe 0%, TMA 10-20%, BKA 40-60%, AKA 90-120%, hip disarticulation 200%+
- Transtibial minimum length: 12-15cm from tibial tuberosity for prosthetic lever arm
- Long posterior flap (Burgess technique) is gold standard for transtibial amputation
- Adductor myodesis to lateral femur prevents abduction contracture in transfemoral
- Syme amputation provides end-bearing but requires experienced surgeon and viable heel pad
Examiner's Pearls
- "Preserve the knee - energy expenditure 40-60% less with BKA vs AKA
- "TcPO2 greater than 30-40 mmHg predicts healing at proposed level
- "Bevel anterior tibia 45 degrees in BKA to prevent skin pressure
- "Fibula cut 1-2cm shorter than tibia to prevent pressure symptoms
Critical Lower Limb Amputation Level Exam Points
Energy Expenditure by Level
This is an EXAM FAVOURITE. Energy cost increases with proximal amputation. Toe/ray: baseline. TMA: 10-20% increase. Transtibial: 40-60% increase. Transfemoral: 90-120% increase. Hip disarticulation: greater than 200% increase. Knee preservation is paramount - reduces energy by 40-60%.
Level Selection Algorithm
Choose the most distal level that will heal. Consider: (1) Tissue viability - TcPO2, Doppler, clinical assessment (2) Functional requirements - prosthetic fitting, mobility goals (3) Patient factors - age, comorbidities, rehabilitation potential. Vascular surgery input essential in PVD.
Key Technical Points by Level
Transtibial: Long posterior flap (Burgess), 45-degree anterior tibial bevel, fibula 1-2cm shorter, myodesis. Transfemoral: Equal anterior-posterior flaps, adductor myodesis to lateral femur (prevents abduction contracture), minimum 10-12cm from greater trochanter.
Prosthetic Considerations
Adequate bone length for lever arm and soft tissue padding for socket. End-bearing levels (Syme, knee disarticulation) allow direct weight transfer. Transtibial requires PTB (patellar tendon bearing) socket. Transfemoral uses ischial containment socket. Early prosthetist involvement essential.
Lower Limb Amputation Levels - Comprehensive Comparison
| Level | Energy Increase | Healing Rate | Prosthetic Outcome | Key Consideration |
|---|---|---|---|---|
| Toe/Ray amputation | 0-5% | Variable (60-80%) | No prosthesis needed | High revision rate in PVD, watch for transfer ulcers |
| Transmetatarsal (TMA) | 10-20% | 70-80% | Toe filler in shoe | Achilles lengthening prevents equinovarus |
| Lisfranc/Chopart | 20-40% | 60-75% | Difficult prosthetic fitting | Equinus deformity common, rarely performed |
| Syme (ankle disarticulation) | 20-40% | 75-85% | End-bearing, long lever arm | Requires viable heel pad, experienced surgeon |
| Transtibial (BKA) | 40-60% | 70-85% | PTB socket, excellent function | MOST IMPORTANT: Preserve the knee |
| Knee disarticulation | 60-80% | 85-90% | End-bearing, bulky knee | No bone cut, good for non-ambulatory |
| Transfemoral (AKA) | 90-120% | 90-95% | Ischial containment socket | Adductor myodesis prevents abduction contracture |
| Hip disarticulation | Greater than 200% | 95%+ | Canadian hip prosthesis, limited use | Reserved for tumor, trauma - high mortality in vascular |
TOES To THIGHAmputation Level Hierarchy
Memory Hook:From TOES To THIGH - more proximal = more energy, less function
FLAPSTranstibial Amputation Technique
Memory Hook:Good FLAPS make a good stump - remember the Burgess long posterior flap
ZERO TO DOUBLEEnergy Expenditure by Amputation Level
Memory Hook:ZERO TO DOUBLE - energy goes from zero to more than double as you go proximal
Overview and Level Selection Principles
Lower limb amputation levels range from toe amputation to hemipelvectomy. The choice of level is critical and determines functional outcome, prosthetic options, energy expenditure, and quality of life.
Key Principles of Level Selection:
- Most distal level that will heal - balance function against healing potential
- Preserve joints - especially the knee (reduces energy by 40-60%)
- Adequate bone length for prosthetic lever arm
- Sufficient soft tissue for durable, well-padded closure
- Consider prosthetic requirements - early prosthetist involvement
The Golden Rule of Amputation
PRESERVE THE KNEE AT ALL COSTS. A short transtibial amputation that heals is vastly superior to a transfemoral amputation. Energy expenditure for ambulation with transtibial is 40-60% less than transfemoral. Even a very short transtibial (Mazet level) preserves knee proprioception and reduces energy demands.
Amputation Level Categories:
Foot Level Amputations
- Toe amputation: Distal phalanx or toe disarticulation
- Ray amputation: Metatarsal and toe en bloc
- Transmetatarsal (TMA): Through metatarsal shafts
- Lisfranc: Tarsometatarsal disarticulation
- Chopart: Midtarsal disarticulation
Major Limb Amputations
- Syme: Ankle disarticulation with heel pad
- Transtibial (BKA): Most common major amputation
- Knee disarticulation: Through-knee amputation
- Transfemoral (AKA): Above-knee amputation
- Hip disarticulation: Complete limb removal
Pathophysiology and Energy Expenditure
Energy Expenditure in Amputation
Energy expenditure during ambulation increases with more proximal amputation levels. This is a critical exam topic and understanding the physiology is essential.
Mechanisms of Increased Energy:
- Loss of normal gait biomechanics - compensatory movements required
- Increased hip and trunk muscle work - to stabilize prosthesis
- Loss of ankle push-off - significant energy generator in normal gait
- Increased swing phase energy - heavier prosthetic components proximally
- Compensatory arm swing - increased upper body work
Energy Expenditure by Amputation Level
| Amputation Level | % Increase Above Baseline | Walking Speed (% of normal) | Oxygen Consumption |
|---|---|---|---|
| Toe/Ray amputation | 0-5% | 95-100% | Minimal increase |
| Transmetatarsal | 10-20% | 85-95% | Slight increase |
| Syme amputation | 20-40% | 75-90% | Moderate increase |
| Transtibial (BKA) | 40-60% | 65-80% | Significant increase |
| Knee disarticulation | 60-80% | 55-70% | Substantial increase |
| Transfemoral (AKA) | 90-120% | 40-60% | Near doubling |
| Hip disarticulation | Greater than 200% | Less than 40% | More than double baseline |
Energy Expenditure - Exam Favourite
Know these numbers: Transtibial (BKA) = 40-60% increase. Transfemoral (AKA) = 90-120% increase. This represents the energy SAVINGS of preserving the knee. Elderly vascular patients often cannot compensate for the energy demands of transfemoral amputation - many become wheelchair-bound.
Healing Considerations by Level
Factors Affecting Healing:
- Vascular supply - TcPO2, Doppler signals, clinical perfusion
- Tissue quality - infection, radiation, previous surgery
- Patient factors - diabetes, smoking, nutrition, renal disease
- Surgical technique - tension-free closure, adequate flaps
General Healing Rates by Level:
- More distal amputations have lower healing rates in vascular disease
- Transfemoral heals reliably (greater than 90%) but at functional cost
- Failed distal amputation requiring revision is worse than primary proximal
TcPO2 for Level Selection
Transcutaneous oxygen tension (TcPO2) predicts healing:
- Greater than 40 mmHg: High probability of healing
- 20-40 mmHg: Indeterminate - clinical judgment required
- Less than 20 mmHg: High probability of healing failure
Always request TcPO2 at proposed amputation level in vascular patients.
Clinical Presentation and Level Assessment
Indications for Each Amputation Level
Foot Level Amputations (Toe, Ray, TMA)
Toe Amputation Indications:
- Localized gangrene of single toe
- Osteomyelitis limited to phalanges
- Frostbite with demarcated necrosis
- Trauma with non-viable toe
Ray Amputation Indications:
- Gangrene extending to metatarsal head
- Osteomyelitis involving MTPJ
- Deep space infection requiring drainage
- Central ray for web space infection
Transmetatarsal Amputation (TMA) Indications:
- Multiple toe gangrene
- Forefoot osteomyelitis
- Failed toe/ray amputations
- Adequate midfoot perfusion
Key Considerations:
- High revision rate in vascular disease (30-50%)
- Watch for transfer ulcers on remaining toes
- Achilles lengthening may be needed with TMA to prevent equinovarus
- Requires adequate midfoot blood supply
Level Selection Algorithm
Level Selection Decision-Making Process
Determine the underlying cause:
- Vascular: Assess perfusion, revascularization options
- Trauma: Injury pattern, soft tissue viability
- Infection: Sepsis control, staged approach
- Tumour: Margin requirements, staging
Vascular assessment:
- Clinical: Pulses, capillary refill, tissue viability
- TcPO2: Greater than 30-40 mmHg predicts healing
- Doppler: Ankle-brachial index, toe pressures
- Angiography if revascularization considered
Patient factors:
- Age and baseline mobility
- Cognitive function for prosthetic training
- Contralateral limb status
- Upper limb function (for transfers)
- Social support and living situation
Hierarchy of preservation:
- Preserve foot if possible (toe, ray, TMA)
- Preserve ankle (Syme) if heel pad viable
- PRESERVE KNEE - transtibial if possible
- Transfemoral if knee not salvageable
- Hip disarticulation only if absolutely necessary
Team involvement:
- Vascular surgery input for level in PVD
- Prosthetist early involvement
- Rehabilitation medicine
- Pain service (phantom pain prevention)
- Psychological support
Investigations for Level Selection
Investigation Protocol for Amputation Level Planning
Essential for vascular disease patients:
- Ankle-brachial index (ABI): Less than 0.4 suggests poor healing
- Toe pressures: Greater than 30 mmHg associated with healing
- TcPO2 at proposed levels: Greater than 30-40 mmHg predicts healing
- Duplex ultrasound: Arterial and venous patency
- CT angiography: If revascularization being considered
Standard assessment:
- Plain radiographs of affected limb
- Assess extent of bone disease (osteomyelitis, tumour)
- Contralateral limb assessment (vascular patients often bilateral)
Advanced imaging (when indicated):
- MRI for tumour margins, skip metastases
- CT for complex trauma, bone quality
- Nuclear medicine for infection localization
Preoperative optimization:
- FBC, coagulation: Anaemia, bleeding risk
- U and E, creatinine: Renal function (affects healing)
- HbA1c: Diabetes control (target less than 8%)
- Albumin, prealbumin: Nutritional status (greater than 30 g/L)
- CRP, ESR: Infection markers
- Blood cultures: If sepsis suspected
Team consultations:
- Vascular surgery: Revascularization options, level advice
- Prosthetist: Socket requirements, level optimization
- Anaesthesia: Perioperative pain plan (phantom pain prevention)
- Rehabilitation medicine: Function potential assessment
- Dietitian: Nutritional optimization
TcPO2 is Key for Level Selection
TcPO2 (Transcutaneous Oxygen Tension):
- Greater than 40 mmHg: 90%+ probability of healing
- 30-40 mmHg: 75-90% probability - usually proceed
- 20-30 mmHg: 50-75% - indeterminate, clinical judgment
- Less than 20 mmHg: Less than 50% - consider more proximal level
Request TcPO2 at BOTH the proposed level AND one level proximal.
Imaging Gallery - Prosthetic Outcomes
Management Principles by Level
Universal Principles for All Levels
Preoperative:
- Optimize medical comorbidities (diabetes, cardiac, renal)
- Smoking cessation (refer to Quitline 13 78 48)
- Nutritional optimization (albumin greater than 30 g/L)
- Early prosthetist involvement
- Psychological preparation and support
Intraoperative:
- Appropriate level based on healing potential
- Adequate bone length for lever arm
- Sufficient soft tissue for tension-free closure
- Myodesis (muscle to bone) for optimal function
- Proper nerve handling - traction neurectomy
Postoperative:
- Rigid dressing or IPOP (immediate post-op prosthesis)
- Edema control - compression
- Phantom pain management
- Early rehabilitation and prosthetic fitting
- Psychological support
Myodesis vs Myoplasty
Myodesis = muscle sutured directly to bone through drill holes or anchors Myoplasty = muscle sutured to opposing muscle or fascia
Myodesis is the gold standard - provides:
- Physiological muscle tension
- Better proprioception
- Stable residual limb shape
- Improved prosthetic control
Surgical Technique by Level
Toe Amputation Technique
Indications: Localized gangrene, osteomyelitis of phalanx, frostbite
Technique:
- Racquet incision around base of toe
- Disarticulate at MTPJ or PIPJ
- Identify and ligate digital vessels
- Transect digital nerves under traction
- Close with interrupted sutures
- Leave open if infected (delayed primary closure)
Ray Amputation Technique
Indications: Gangrene to metatarsal head, MTPJ osteomyelitis
Technique:
- Racquet incision extending onto dorsum of foot
- Incise along metatarsal shaft
- Disarticulate at tarsometatarsal joint (or cut metatarsal)
- Remove metatarsal and toe en bloc
- Preserve intermetatarsal ligaments if possible
- Close with slight narrowing of foot
- Consider first or fifth ray specifically
Ray Amputation Specifics
First ray amputation: Preserves lateral foot but loses medial weight bearing - shifts weight laterally. Fifth ray amputation: Preserves medial column but narrows foot. Central rays (2nd, 3rd): Can be removed with minimal functional loss. Multiple rays: Consider TMA instead if greater than 2 rays involved.
Complications
Wound-Related Complications
Wound Complications by Amputation Level
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Wound infection | 10-20% | Diabetes, PVD, malnutrition | Antibiotics, drainage, debridement |
| Wound dehiscence | 5-15% | Tension closure, poor perfusion | VAC therapy, revision if extensive |
| Wound necrosis/failure | 5-30% (level dependent) | Wrong level selection, PVD | Debridement, proximal revision |
| Hematoma | 5-10% | Poor hemostasis, anticoagulation | Aspiration or surgical evacuation |
Revision Rates by Level:
- Toe/Ray: 30-50% in vascular disease
- TMA: 20-40%
- Transtibial: 10-20%
- Transfemoral: 5-10%
Key Point: More distal amputations have higher revision rates but better function if successful.
Evidence Base
Energy Expenditure in Lower Extremity Amputees
- Seminal study establishing energy expenditure by amputation level
- Transtibial amputation: 40-60% increase in energy above baseline
- Transfemoral amputation: 90-120% increase in energy above baseline
- Walking speed decreases with more proximal amputation
- Vascular amputees have higher energy expenditure than traumatic amputees at same level
LEAP Study - Limb Salvage vs Amputation in Lower Extremity Trauma
- Prospective multicenter study comparing limb salvage vs amputation
- No significant difference in functional outcomes at 2 years
- Salvage group had more secondary procedures and complications
- Psychological outcomes similar between groups
- Cost of salvage significantly higher than amputation
Burgess Long Posterior Myoplasty Flap for Transtibial Amputation
- Described the long posterior myocutaneous flap technique
- Gastrocnemius muscle provides durable, well-vascularized coverage
- Superior healing rates compared to anterior or equal flaps in vascular patients
- Muscle padding improves prosthetic tolerance
- Became the worldwide standard for transtibial amputation
TcPO2 for Amputation Level Selection
- Transcutaneous oxygen tension predicts healing at amputation level
- TcPO2 greater than 40 mmHg: Greater than 90% healing rate
- TcPO2 less than 20 mmHg: High failure rate
- 20-40 mmHg: Indeterminate - requires clinical judgment
- TcPO2 superior to clinical assessment alone
Mirror Therapy for Phantom Limb Pain
- RCT of mirror therapy for phantom limb pain in combat amputees
- Mirror therapy group showed significant pain reduction at 4 weeks
- Control group (covered mirror) showed no improvement
- Proposed mechanism: Visual feedback resolves cortical conflict
- Simple, no-cost intervention with strong evidence
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
"A 72-year-old diabetic male with peripheral vascular disease presents with gangrene of his left forefoot extending to the base of all toes. His previous femoral-popliteal bypass is occluded. TcPO2 at the ankle is 25 mmHg and at 15cm below the knee is 42 mmHg. What amputation level would you recommend and why?"
"Describe the surgical technique for transtibial amputation, highlighting the key technical points that optimize function and prosthetic fitting."
"A 45-year-old man requires transfemoral amputation for a high-grade osteosarcoma of the distal femur. What are the key technical considerations for this amputation that differ from a vascular amputation?"
Australian Context
Epidemiology and Healthcare System
Lower limb amputations in Australia are predominantly performed for peripheral vascular disease and diabetes, reflecting the aging population and high prevalence of lifestyle-related conditions. Indigenous Australians have significantly higher rates of diabetes-related amputations compared to non-Indigenous Australians, with rates up to 38 times higher in some studies, highlighting significant health disparities that require targeted intervention.
The Australian healthcare system provides comprehensive amputation care through public hospital networks, with major centers offering multidisciplinary limb preservation services that include vascular surgery, endocrinology, wound care, and orthopaedic surgery. The introduction of Diabetic Foot Units in major hospitals has improved outcomes by enabling early identification of at-risk patients and coordinated care to prevent amputation where possible. Prosthetic services are funded through various state and territory schemes, with the National Disability Insurance Scheme (NDIS) providing funding for prosthetics for eligible participants under 65 years of age.
Clinical Guidelines and Resources
Australian clinical practice follows the IWGDF (International Working Group on the Diabetic Foot) guidelines for diabetic foot management, and the Australian and New Zealand Society for Vascular Surgery provides guidance on peripheral arterial disease management. Smoking cessation support is available through Quitline (13 78 48), which should be offered to all patients as smoking significantly impairs healing. Antibiotic prescribing follows Therapeutic Guidelines (eTG), with empiric therapy for diabetic foot infections typically covering gram-positive organisms, gram-negatives, and anaerobes. The PBS subsidizes many medications required for vascular disease management, including antiplatelet agents, statins, and diabetes medications, improving access to medical optimization before and after amputation.
Lower Limb Amputation Levels
High-Yield Exam Summary
Energy Expenditure - KNOW THESE NUMBERS
- •Toe/Ray: 0-5% increase
- •TMA: 10-20% increase
- •Syme: 20-40% increase
- •Transtibial (BKA): 40-60% increase
- •Knee disarticulation: 60-80% increase
- •Transfemoral (AKA): 90-120% increase
- •Hip disarticulation: Greater than 200% increase
- •PRESERVE THE KNEE - saves 40-60% energy vs AKA
Transtibial Key Points (FLAPS)
- •Flap: Long posterior (Burgess technique)
- •Length: Minimum 12-15cm from tibial tuberosity
- •Anterior bevel: 45 degrees on tibia
- •Position fibula: 1-2cm shorter than tibia
- •Suture myodesis: Posterior muscles to anterior tibia
Transfemoral Key Points
- •Equal anterior-posterior flaps
- •Minimum 10-12cm from greater trochanter
- •ADDUCTOR MYODESIS to lateral femur - prevents abduction contracture
- •Sciatic nerve - ligate vessel before transection
- •Myodesis of quadriceps and hamstrings over bone
Level Selection Algorithm
- •TcPO2 greater than 40 mmHg: 90%+ healing
- •TcPO2 20-40 mmHg: Indeterminate
- •TcPO2 less than 20 mmHg: High failure risk
- •Vascular surgery input for level in PVD
- •Most distal level that will heal
- •Failed distal worse than primary proximal
Complications to Know
- •Phantom limb pain: 70-80% incidence
- •Knee flexion contracture (BKA): Prone lying, stretching
- •Hip abduction contracture (AKA): Adductor myodesis prevents
- •Equinovarus (TMA): TAL prevents
- •Neuroma: Traction neurectomy technique
Emergency Amputation
- •Guillotine amputation for life-threatening sepsis
- •All tissues at same level, no closure
- •VAC dressing
- •Revise in 48-72 hours when stable
- •Life before limb principle