above knee amputation - how it is done
Indication for amputation above knee
The indication for amputation above knee include includes ischemia ( acute or chronic ischemia), infarction, gangrene or cause by severe burns or trauma. The next indication include malignancy such as certain tumours ( osteosacroma or malignant melanoma). Severe infection such as gas gangrene ( clostridium perfringens) or necrotising fasciitis and rare cause such as intractable ulceration or painful paralysed limbs may also indicates the need for amputation.
Anatomy of the amputation.
Amputation above knee include above knee amputation at the level of 15cm above the tibial plate and through knee amputation that is indicated ( if there has been prior orthopaedic fixation of femur ) but the disadvantages is unpredictable healing of skin flaps and bulbous stump with difficult prosthesis fitting. Gritti -stokes amputation involve femur division at the supracondylar level, leaving a longer stump than above knee amputation and increase instability for the patient while sitting. other variants of above knee amputation includes disarticulation of the hip and hindquarter amputation which are rarely done and mainly performed for severe cases such as infection or malignancy.
Pre operation preparation ideally involve multidisciplinary assessment including surgical, anaesthetic, prosthetic specialist. Assessment of the level of amputation based on severity of the disease and patient factors ( e.g rehabilitation prospects). Insulin sliding scale if diabetic, blood test, cross match blood and urinary catheterization if appropriate.
Post operation involve deep vein thrombosis prophylaxis. Rehabilitation with early physiotherapy, early walking aids ( e.g pneumatic post - amputation mobility aid ) or prosthesis fitting.
Access- Two equal fish mouth - shaped skin flaps are marked on the skin, with their upper ends at the level of femur transaction. This is 15cm above the tibial plateau.
Muscle and vessel ligation- during skin incision, the long saphenous vein is ligated and the muscles of the anterior and posterior thigh compartments divided by diathermy. Vastus lateralis is sutured to the adductors and quadriceps to the hamstrings. Arteries and veins are ligated and nerves divided cleanly under gentle traction.
Bone amputation- the femur is stripped of periosteum and divided with filling of bone ends to create a smooth surface.
Closure- Once haemostatis is achieved, the two myoplastic flaps are brought together and the skin is closed with interrupted sutures. A suction vacuum drain may be left in situ.
Complication of the procedure
Early complication includes pain, deep vein thrombosis, flap ischemia, stump hematoma, neuroma or infection, stump length too long or too short, bony spurs and psychological problems.
late complication includes 'phantom limb' pain ( reduced by strong analgesic post operation ), neuroma formation, erosion of bone through skin, ischemia, osteomyelitis and ulceration. Amputations are most often carried out in those with concomitant severe atherosclerotic disease and there is a major risk of other vascular problems with survival only 30% at 5 years post - amputation.