Above-Knee Amputation (Transfemoral)

Primary Indications

Absolute / Common Indications

• Dysvascular / diabetic limb with critical ischaemia or extensive tissue loss not amenable to below-knee amputation (inadequate distal perfusion or unsalvageable posterior flap)
• Severe trauma with non-reconstructable limb, or failed limb salvage where the knee cannot be preserved
• Life-threatening infection / necrotising soft-tissue infection or wet gangrene extending proximal to a viable transtibial level
• Tumour requiring proximal margins where limb-sparing surgery is not feasible
• Non-functional limb (fixed deformity, paralysis, intractable pain) where a transfemoral residual limb is more useful than the diseased limb

Relative Indications

• Failed transtibial amputation requiring revision to a higher level
• Severe knee flexion contracture making a transtibial prosthesis unworkable
• Multiply revised, chronically infected transtibial stump

Contraindications / Cautions

• A viable transtibial level achievable - preserve the knee whenever possible for the metabolic and rehabilitation advantage
• Patient who is a candidate for successful revascularisation should have vascular assessment first
• Proximal disease that will not heal at the transfemoral level may require hip disarticulation

Level Selection and the Energy / Mobility Trade-off

The single most important strategic decision is how proximal to amputate. Each level preserved below the knee dramatically improves function.

Energy Expenditure

• Walking after amputation costs more oxygen and is slower with each more proximal level. Waters' classic gait-laboratory work demonstrated a stepwise rise in energy cost from transtibial to transfemoral amputation, with the dysvascular transfemoral amputee having the highest oxygen cost per metre and the slowest comfortable walking speed.
• The knee joint and the lever arm of a longer residual limb are biomechanically efficient; losing the knee removes a key shock-absorbing and energy-storing joint.

Prosthetic Rehabilitation / Mobility

• A substantial proportion of dysvascular transfemoral amputees never achieve independent prosthetic ambulation, in contrast with the higher community-ambulation rates after transtibial amputation.
• Predictors of successful prosthetic mobility include younger age, better cognition, absence of contralateral limb disease, and good cardiovascular reserve. Tools such as the AMPREDICT model help quantify the probability of prosthetic mobility and inform realistic counselling.

Practical Rule

• Save the knee if the tissue allows it. Choose transfemoral amputation only when a healed, functional transtibial stump is not achievable - the trade-off is fewer wound complications/healing at the higher level versus a major loss of walking economy and independence.

Evidence Base

Myodesis vs Myoplasty

• Myodesis (suturing muscle directly to bone through drill holes) produces a stable, dynamic stump with maintained muscle tension - particularly adductor magnus myodesis to restore femoral adduction. Gottschalk's biomechanical work showed that failure to reattach the adductor magnus allows the femur to drift into abduction and flexion, shortening the adductor lever and impairing prosthetic gait.
• Myoplasty (suturing opposing muscle groups to each other over the bone end) is technically simpler and may be preferred when bone fixation is unsafe, but the muscle envelope is less securely anchored and may retract, giving weaker adduction control.

Healing and Outcomes

• Transfemoral amputation has a higher primary healing rate than transtibial in poorly perfused limbs, which is precisely why it is chosen when a BKA would fail - but this gain is offset by inferior functional outcome.
• Mortality after major dysvascular lower-limb amputation is high, reflecting the comorbid (diabetic, cardiovascular) population rather than the operation itself - this must frame pre-operative counselling.

Key Evidence

Cross-sectional Anatomy of the Thigh

Compartments and Muscles

• Anterior compartment (quadriceps): rectus femoris, vastus lateralis/medialis/intermedius - innervated by the femoral nerve; provides the anterior myofascial flap.
• Medial compartment (adductors): adductor longus, brevis, magnus, gracilis - obturator nerve. Adductor magnus is the key muscle for myodesis to maintain femoral adduction.
• Posterior compartment (hamstrings): biceps femoris, semitendinosus, semimembranosus - sciatic (tibial division) nerve; contributes to the posterior flap and hip extension.

Femur

• The femoral shaft is the structure transected. Ideal residual length is approximately 12 cm above the knee joint line (measured from the joint, or roughly 25-30 cm from the greater trochanter in an average adult) to leave room for the prosthetic knee mechanism.
• The anterior cortex is bevelled to remove the sharp distal edge and prevent a painful skin-tenting prominence under the socket.
• A longer femur improves the lever arm and prosthetic control - so length is preserved as much as healing permits, balanced against leaving room for the knee unit.

Neurovascular Structures

• Superficial femoral artery and vein: traverse the adductor (Hunter's, subsartorial) canal on the medial side, passing from the anterior compartment toward the popliteal fossa through the adductor hiatus. These are the principal vessels to identify and doubly ligate.
• Profunda femoris (deep femoral) branches: muscular perforators that must be controlled during muscle division.
• Sciatic nerve: lies deep in the posterior compartment, posterior to adductor magnus and the femur. It carries the small arteria comitans nervi ischiadici which must be ligated to avoid bleeding when the nerve is divided.
• Cutaneous nerves (e.g. posterior femoral cutaneous, branches of the saphenous nerve medially) cross the flaps and contribute to neuroma/scar sensitivity if handled roughly.

Hip Muscle Balance (Functional Anatomy)

• Detaching the adductors and hamstrings leaves the abductors (gluteus medius/minimus) and flexors (iliopsoas, rectus femoris) relatively unopposed.
• The unbalanced pull drives the residual femur into abduction and flexion - the basis of the dreaded abduction-flexion contracture.
• Adductor magnus myodesis is the surgical antidote: re-anchoring the adductor restores the adduction moment and a more neutral femoral position for prosthetic alignment.

Positioning and Preparation

Patient Position: Supine, with a sandbag or bump under the ipsilateral buttock/hip to allow access to the posterior thigh. Mark the proposed bone level and flaps before draping.

Technical Points:

• Confirm the side and level against imaging and the vascular assessment.
• Prepare and drape to allow circumferential access to the thigh.
• A thigh tourniquet may be used in trauma/tumour but is generally avoided in dysvascular cases to allow assessment of tissue bleeding and viability.

Anaesthesia: General or regional (spinal/epidural). Pre-emptive / perioperative analgesia (regional block, gabapentinoids) is used to reduce acute and persistent phantom limb pain.

Operative Steps

Step 1: Mark Bone Level and Flaps

• Plan bone section approximately 12 cm above the knee joint line (or as dictated by tissue viability/tumour margin).
• Design equal anterior and posterior (fish-mouth) flaps; total combined flap length should equal approximately the diameter of the thigh at the level of bone section so closure is tension-free.
• In trauma, use viability rather than geometry to dictate flaps - "amputate at the lowest viable level with whatever flaps the soft tissue allows."

Step 2: Skin and Subcutaneous Incision

• Incise skin and fat along the marked fish-mouth, raising flaps as fasciocutaneous-myocutaneous units, not thin skin flaps, to preserve perfusion.
• Handle skin with hooks rather than crushing forceps in the dysvascular limb.

Step 3: Divide the Anterior and Medial Muscles; Identify the Femoral Vessels

• Divide the quadriceps anteriorly, bevelling the muscle distal-to-proximal so it can be folded over the bone end.
• Identify the superficial femoral artery and vein in the adductor canal medially.

Step 4: Ligate the Major Vessels

• Dissect the artery and vein free and doubly ligate each separately with non-absorbable suture (a transfixion ligature plus a proximal simple tie for the artery).
• Control profunda perforators and muscular branches with ties or cautery as muscles are divided.

Step 5: Divide the Posterior Muscles and Address the Sciatic Nerve

• Divide the hamstrings to expose the sciatic nerve in the posterior compartment.
• Ligate the accompanying vessel (arteria comitans), then apply gentle distal traction to the nerve and divide it sharply with a fresh blade so the cut end retracts proximally into muscle, away from the bone end and scar. Avoid crushing or excessive traction.

Step 6: Transect the Femur

• Strip a short cuff of periosteum, then transect the femur with an oscillating saw at the planned level (~12 cm above the knee).
• Bevel the anterior cortex and file/rasp all edges smooth to remove sharp prominences. Irrigate away bone debris.

Step 7: Adductor Magnus Myodesis

• Drill holes in the lateral cortex of the distal femur.
• Bring the adductor magnus across the bone end under physiological tension with the hip held in neutral/adduction, and suture it through the drill holes - this is the myodesis that maintains the adduction moment and prevents abduction contracture.
• (If bone fixation is unsafe, e.g. very osteoporotic/infected bone, a myoplasty suturing adductors to the posterior/quadriceps fascia is the alternative.)

Step 8: Myofascial Coverage of the Bone End

• Bring the bevelled quadriceps over the distal femur and secure to the posterior musculature/fascia, providing a stable, padded myofascial cover with the femur held in adduction.
• Avoid bulky, redundant muscle that compromises socket fit.

Step 9: Haemostasis

• Release any tourniquet and obtain meticulous haemostasis - haematoma is a major cause of wound breakdown in dysvascular tissue.
• Confirm the cut muscle and skin edges bleed (viability) in non-tourniquet cases.

Step 10: Drain

• Place a closed suction drain deep to the muscle layer, brought out away from the suture line; remove at 24-48 h depending on output.

Step 11: Closure

• Close the deep fascia/muscle envelope, then subcutaneous tissue and skin without tension.
• Skin closed with interrupted sutures or staples; the scar should lie away from the weight-bearing distal end.

Step 12: Dressing

• Apply a rigid plaster dressing (shapes the stump, controls oedema, protects from trauma, may speed prosthetic readiness) or a soft compressive dressing with stump bandaging - choice depends on local practice and ability to monitor the wound.
• Position the hip in neutral extension and adduction; avoid pillows under the stump.

Specific Management Pearls

Preventing the Abduction-Flexion Contracture

• This is the most examinable functional complication. The mechanism is unopposed abduction and flexion once the adductors and hamstrings are released.
• The surgical answer is adductor magnus myodesis; the nursing/therapy answer is neutral positioning, no pillow under the stump, and daily prone lying.

Revision to a Higher Level

• Driven by non-healing flap necrosis or uncontrolled infection in poorly perfused tissue.
• Re-assess vascular status; ensure the new level has bleeding, viable tissue. Hip disarticulation is the next level if the proximal thigh is non-viable - a major functional and metabolic step-down.

Managing the High-Risk Patient

• The dysvascular transfemoral population carries high perioperative mortality from cardiovascular/diabetic comorbidity. Optimise medically, counsel realistically about survival and the lower likelihood of independent prosthetic walking.

Immediate Post-operative Phase (0-2 Weeks)

Dressing and Positioning

• Rigid dressing (plaster cast) or soft compressive stump bandage to shape the residual limb and control oedema; rigid dressings also protect from trauma and may shorten time to prosthetic casting.
• Position the hip in neutral extension and adduction. Do NOT place a pillow under the stump (promotes hip flexion contracture) and avoid prolonged sitting with the hip flexed.

Pain Management

• Multimodal analgesia: paracetamol + NSAIDs (if not contraindicated), regional catheter where used, and neuropathic agents (gabapentin/pregabalin, amitriptyline) to address phantom and neuroma pain.
• Distinguish stump (residual-limb) pain from phantom limb pain - different management emphasis.

Wound and Drain Care

• Monitor for haematoma, dusky flaps, and infection; the dysvascular flap is vulnerable.
• Remove the suction drain at 24-48 h. Sutures/staples out at about 2-3 weeks (later than usual given slow dysvascular healing).

Intermediate Phase (2-6 Weeks)

Contracture Prevention and Strengthening

• Daily prone lying to stretch the hip flexors and prevent flexion contracture.
• Strengthen hip extensors and the remaining adductors; maintain core and contralateral limb strength.
• Stump desensitisation and oedema control with shrinker socks/compression once the wound is healed.

Early Mobilisation

• Wheelchair independence and transfers; gait re-education with the physiotherapist.
• Address the contralateral limb - it is often also at vascular/diabetic risk and is now bearing extra load.

Rehabilitation and Prosthetics (6 Weeks Onward)

Prosthetic Prescription

• Cast for a prosthetic socket once the stump has healed and matured (volume stabilised).
• Components reflect activity level: an ischial-containment or sub-ischial socket, an appropriate prosthetic knee unit (the femur was left short enough to accommodate it), and a foot/ankle matched to mobility goals.
• Set realistic expectations: many older dysvascular transfemoral amputees achieve household rather than community ambulation; energy cost of walking is substantially higher than with a transtibial prosthesis.

Energy and Mobility Counselling

• Reinforce why the knee mattered: walking is slower and far more demanding without it. This frames goal-setting and the choice between a prosthesis and a wheelchair-based lifestyle for frail patients.

Long-term Monitoring

Follow-up

• Serial review of stump volume and skin, socket fit, and gait.
• Surveillance and protection of the contralateral limb (foot care, glycaemic and vascular control) to avoid bilateral amputation.

Outcome Assessment

• Functional measures (mobility grade, walking distance), prosthetic use, and quality-of-life tools.
• Ongoing pain review for phantom/neuroma symptoms.

Warning Signs Requiring Review

• Non-healing or breaking-down wound, increasing pain or discharge (infection/necrosis).
• Developing fixed hip flexion/abduction posture (contracture).
• New rest pain or tissue changes in the contralateral limb.