Amputation — Levels & Prosthetics

Overview & Indications

Amputation is the surgical removal of a limb or part of a limb, performed when the limb is non-salvageable, non-functional, or represents a greater threat to the patient`s life than its removal. Far from representing surgical failure, a well-planned amputation at the correct level, followed by excellent prosthetic rehabilitation, often returns the patient to a higher functional level than a failed limb salvage attempt. The choice of amputation level is the most critical surgical decision — it determines the energy cost of walking with a prosthesis, the prosthetic options available, and the rehabilitation potential.

Indications for amputation: (1) Vascular — peripheral arterial disease (PAD) with critical ischaemia and non-reconstructable disease; diabetic foot with gangrene; (2) Trauma — unsalvageable limb (Gustilo IIIC with non-reconstructable vascular injury; mangled extremity); the LEAP study (Lower Extremity Assessment Project) demonstrated equivalent functional outcomes between amputation and limb salvage for severe lower extremity injuries at 2-year follow-up — the decision between limb salvage and amputation should not be based on scoring systems alone; (3) Tumour — malignant bone or soft tissue tumours not amenable to limb salvage; (4) Infection — uncontrolled life-threatening sepsis (gas gangrene, necrotising fasciitis) not responding to debridement; (5) Congenital deformity — non-functional limb or planned amputation to facilitate superior prosthetic fitting
Mangled extremity scoring systems: the Mangled Extremity Severity Score (MESS) assesses skeletal/soft tissue injury (1–4), limb ischaemia (1–6), shock (0–2), and patient age (0–2); MESS ≥7 = high likelihood of amputation; however scoring systems are NOT absolute — they guide but do not replace clinical judgement; the LEAP study showed MESS poorly predicted functional outcomes

Amputation Levels — Lower Limb

Level	Description	Prosthetic Options	Key Considerations
Syme`s amputation	Disarticulation through the ankle joint with preservation of the heel pad; the heel pad (a tough, specialised weight-bearing skin) is transposed to cover the distal tibia stump; the malleoli may be trimmed to reduce the bulbous stump profile	End-bearing stump — the patient can walk short distances without a prosthesis (on the stump itself); low-profile prosthetic foot; good cosmesis challenge due to bulbous stump	Best level for diabetic foot salvage; preserves maximum limb length; end-bearing capacity unique advantage; requires intact heel pad vascularity (posterior tibial artery must be patent); poor cosmesis (bulbous stump)
Below-knee (BK) / Transtibial (TT)	Amputation through the tibial shaft; the ideal stump length is the distal 1/3 of the tibia at approximately 12–15 cm from the tibial tuberosity; the fibula is divided slightly shorter than the tibia (1–2 cm) to avoid fibular prominence; long posterior myocutaneous flap (Burgess flap) is the standard closure technique — gastrocnemius-soleus muscle and posterior skin provide excellent padding over the distal stump	Endoskeletal pylon with prosthetic foot; modern energy-storing carbon fibre feet (Flex-Foot, Össur Cheetah); microprocessor ankles; wide range of high-performance prosthetics available	The ideal functional lower limb amputation level; preserves the knee joint (the single most important determinant of walking energy cost and rehabilitation success); energy cost of walking with TT prosthesis ~25–40% above normal; 80–90% of transtibial amputees achieve community-level ambulation
Knee disarticulation (KD)	Disarticulation through the knee joint; the femoral condyles are preserved; provides a long end-bearing stump with excellent proprioception; the patella is retained and sutures to provide anterior padding	Specialised KD prosthetic knee joints; the bulbous femoral condyles create cosmetic challenges with prosthetic fitting; polycentric prosthetic knees required to maintain equal knee centre height	Preferred over above-knee (AK) in children (preserves the distal femoral physis — allows continued bone growth); provides excellent suspension and proprioception; less commonly performed in adults due to prosthetic challenges; better rehabilitation potential than AK due to longer lever arm and end-bearing capacity
Above-knee (AK) / Transfemoral (TF)	Amputation through the femoral shaft; ideal stump length 50–65% of the femoral length (approximately 10–12 cm above the knee joint level); adductor myodesis (suturing the adductor muscles to the lateral femur) maintains adductor pull and prevents abduction contracture and hip flexion deformity — critical for prosthetic fitting; equal anterior and posterior myocutaneous flaps	Prosthetic knee joints: mechanical (single-axis, polycentric), hydraulic, microprocessor-controlled (C-Leg, Rheo Knee — stance and swing phase control); prosthetic foot; socket fit is critical; ischial weight-bearing socket or total surface-bearing socket	The knee is lost — dramatically increases rehabilitation challenge and energy cost; energy cost of walking with TF prosthesis ~65–100% above normal; only 50–60% of TF amputees achieve community-level ambulation; adductor myodesis is the most critical technical step — prevents the stump falling into abduction which makes prosthetic fitting impossible; hip flexion and abduction contracture are the worst complications
Hip disarticulation	Disarticulation through the hip joint; the entire femur is removed; performed for proximal femoral tumours, extensive trauma, or severe proximal vascular disease	Canadian hip disarticulation prosthesis; hip, knee, and ankle units; extremely high energy cost of ambulation; many patients choose wheelchair over prosthetic walking	Energy cost of ambulation is very high (~100–125% above normal); only highly motivated young patients achieve functional prosthetic ambulation; most patients with hip disarticulation from trauma or tumour achieve best function with a wheelchair and a cosmetic prosthesis

Amputation Levels — Upper Limb

Level	Prosthetic Options	Key Points
Digit / partial hand	Cosmetic or functional prosthetic digits (silicone); myoelectric fingers (i-Limb)	Preserve maximum length; replantation preferred for thumb and multiple digit amputations if viable; even a short thumb stump is more functional than a prosthesis
Below-elbow / Transradial (TR)	Body-powered hook (Hosmer); myoelectric hand (Ottobock); hybrid; activity-specific terminal devices	Preserve maximum length; even a very short transradial stump (3–4 cm) is functionally superior to a transhumeral amputation (pronation/supination is partially preserved); myoelectric prostheses are the modern standard for upper limb amputees
Above-elbow / Transhumeral (TH)	Myoelectric elbow + hand; body-powered cable-driven system; microprocessor elbow	Loss of elbow dramatically reduces prosthetic function; elbow disarticulation preferred over short TH stump for prosthetic fitting; the elbow joint provides prosthetic anchoring
Forequarter / Shoulder disarticulation	Cosmetic shoulder cap ± passive or myoelectric arm; most patients choose cosmesis over functional prosthesis at this level	Performed for proximal upper extremity sarcomas or catastrophic vascular injuries; body-powered prosthetics achieve limited function; cosmesis is often the primary goal

Surgical Principles & Stump Construction

Stump length: `preserve as much length as possible` within the constraints of adequate vascularity, soft tissue coverage, and prosthetic requirements; the minimum functional stump lengths are: transtibial — 5 cm of tibia below the tibial tuberosity (8–12 cm is ideal — long posterior flap technique allows longer stumps than equal flaps); transfemoral — 10 cm below the lesser trochanter; the stump must be long enough to provide a lever arm for prosthetic control
Myodesis vs myoplasty: myodesis = direct muscle attachment to bone (drill holes through the cortex to suture the muscle); provides better muscle control and proprioception; prevents retraction of muscles; myoplasty = suturing muscles to each other over the bone end (muscle to muscle); less rigid fixation; myodesis is preferred for transfemoral amputation (adductor myodesis is critical); both techniques are used in transtibial amputation
Nerve management: all major nerves should be identified, put under gentle tension, and sharply divided — they are allowed to retract proximally into soft tissue away from the stump end; this reduces the risk of painful neuroma formation; do NOT tie or cauterise the nerve — these techniques increase neuroma pain; a `traction neurectomy` (gentle pull + sharp cut) allows the nerve end to retract into a soft tissue bed away from the prosthetic socket contact area
Bone management: sharp bone edges are bevelled and smoothed with a rasp to prevent pressure sores under the prosthetic socket; the tibia is bevelled anteriorly at approximately 45° at the stump end; the fibula is cut 1–2 cm shorter than the tibia to avoid fibular prominence; the bone end must be covered with healthy muscle and skin — never allow bone to contact the skin directly

Prosthetics & Rehabilitation

Energy cost of walking (O2 consumption above normal): partial foot ~10%; Syme`s ~15%; transtibial ~25–40%; knee disarticulation ~50%; transfemoral ~65–100%; hip disarticulation ~100–125%; bilateral transtibial ~41%; bilateral transfemoral ~280%; these figures demonstrate why preservation of the knee joint is the single most important goal in lower limb amputation surgery — the energy cost increase between transtibial and transfemoral is enormous; elderly patients with cardiovascular disease may not have the cardiorespiratory reserve to ambulate at the energy cost of a transfemoral amputation
Prosthetic categories — lower limb: (1) Energy-storing/returning (ESR) feet — carbon fibre blade design; store energy in stance and release it at push-off (e.g., Össur Vari-Flex, Ottobock Taleo Carbon); allow running and sports; (2) Microprocessor knees (MPK — for transfemoral amputees) — C-Leg (Ottobock), Rheo Knee (Össur); hydraulic microprocessor-controlled stance and swing phase; dramatically reduce falls and improve community ambulation; (3) Osseointegration — titanium implant anchored in the residual bone; the prosthesis attaches directly to the implant (percutaneous abutment); eliminates socket fit problems; allows direct osseous feedback (osseoperception); growing evidence for improved function and quality of life
Phantom limb pain: experienced by 50–80% of amputees; the sensation of pain in the absent limb; distinguished from phantom sensation (non-painful awareness of the absent limb) and residual limb (stump) pain; managed with: mirror therapy (most evidence-based conservative approach); graded motor imagery; gabapentinoids; amitriptyline; TENS; ketamine infusions in refractory cases; early prosthetic fitting reduces phantom pain

Exam Pearls

Most important principle: preserve the knee joint; transtibial (BK) vs transfemoral (AK) is the most critical amputation decision; energy cost of TT = 25–40% above normal; AK = 65–100% above normal; elderly/vascular patients may not achieve ambulation at AK energy cost
Syme`s amputation: ankle disarticulation preserving the heel pad; end-bearing; patient can walk on stump without prosthesis; ideal for diabetic foot with patent posterior tibial artery; bulbous stump = cosmetic challenge
Transtibial ideal stump: 12–15 cm from tibial tuberosity; fibula 1–2 cm shorter; long posterior myocutaneous flap (Burgess); tibia bevelled anteriorly; adductor myodesis NOT required (transfemoral only)
Transfemoral adductor myodesis: the most critical technical step; prevents abduction and flexion contracture of the stump; without myodesis, the adductors retract and the stump falls into abduction making socket fitting impossible; suture adductors to drill holes in the lateral femur under physiological tension
Nerve management: traction neurectomy — gentle tension + sharp cut = nerve retracts into soft tissue; prevents painful neuroma formation at the stump end; never tie, cauterise, or leave nerve at the bone end
LEAP study: equivalent functional outcomes between amputation and limb salvage for severe lower extremity injuries at 2 years; MESS score poorly predicted outcomes; decision should be individualised, not based on scoring alone
Energy storing feet: carbon fibre ESR feet for active amputees; store energy at heel strike, release at toe-off; allow running (Cheetah blade, Flex-Run); microprocessor knees (C-Leg) reduce falls in TF amputees
Phantom limb pain: 50–80% of amputees; mirror therapy has strongest evidence for conservative management; gabapentinoids; graded motor imagery; distinguish from stump pain (local stump pathology — neuroma, infection, bone spur)
Knee disarticulation preferred over short TF in children: preserves distal femoral physis; allows continued femoral growth; prevents the stump-shortening problem of physeal ablation in long bone amputations in skeletally immature patients

Amputation — Levels & Prosthetics

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