Amputation below knee- how it is done?
Indication for amputation below knee
The indication for amputation includes ischemia, infarction, gangrene, severe trauma and burn. It is follow by malignancy such as osteosacroma or malignant melanoma and severe infection such as gas gangrene ( clostirdium perfringens) and necrotising fascitis and rare cause such as intractable ulcer or painful paralysed limbs.
Anatomy of the amputation
The amputation can be divided into three categories such as below knee amputation that includes two technique such as transtibial amputation that requires Buergess long saphenous posterior flap and Robinson's skew flap technique.
Another form of amputation includes ankle level amputation which is seldom perofrmed due to difficulty attaching prosthesis and midfoot amputation that involve Lisfranc's technique invovlving disarticulation betweeb tarsal and metatarsal bones or Chorpart's disarticulartion of the talonavicular and calcaenocuboid joints.
other form of below knee amputation includes Ray's amputation which requires excision of the toe by division through the metatarsal bone and toe amputation that involves division through the proximal phalanx as cutting through, a joint expose avascular cartilage that does not heal well.
Preparation before and after surgery
Pre operative preparation includes multidisciplinary assessment including surgical, anaesthetics, prosthetics specialist, physiotherapist and psychologist. Assessment of the level of amputation given severity of disease and patient factors such as rehabilitation. Insulin sliding scale if diabetic, appropriate blood tests and crossmatch blood, urinary catheterization if appropriate.
The post operative preparation includes deep vein thrombosis prophylaxis, rehabilitation with early physiotherapy, early walking aids ( pneumatic post -amputation mobility aid), prosthesis fitting.
Assess- skin flaps are marked on the skin prior to incision with a longer posterior flap ( Buergess) or skew anteromedial and posterolateral flaps.The level of tibial transaction is 14cm below knee joint or 10-12cm below tibial tuberosity.
Ligation of muscle and vessels- during skin incision the long saphenous vein is ligated and the muscles of the anterior and peroneal compartment divided by diathermy. Arteries and veins are ligated and following diathermy of accompanying vasa nervorum, the tibial nerve divided clearly under general anaesthetics.
Bone amputation - the fibula is divided by 2cm proximally following stripping of periosteum. The tibia is also stripped and divided with filling of bone ends to a smooth surface.
Closure- the posterior flap includes some gastrocnemius muscle to cover the cut tibia, forming a cylindrical stump. After hemostasis is achieved the skin is closed with interrupted sutures. A suction vacuum drains may be left in situ .
Complication from the surgery
Early complication - pain, deep vein thrombosis, flap ischemic, stump hematoma, neuroma or infection, stump length too long or short, bony spurs and psychological problems.
Late complication - 'phantom limb' pain reduced by strong analgesic, neuroma formation, erosion of bone through skin, ischemic, osteomyelitis and ulceration.
Amputations are most often carried out in those with concomitant severe atherosclerotic disease and there is major risk of other vascular problems with survival only 30% at 5 years .