Below knee amputation

The patient is a young man in his late thirties who suffered a severe fracture of his tibial plafond (pilon fracture ) several years ago. He underwent limited internal fixation and stabilised in a fine wire fixator construct. Post operatively he suffered the complication of acute compartment syndrome for which he underwent emergency fasciotomy. No dead or nonviable muscle needed to be excised. He then underwent a delayed closure of his wounds. He continued to suffer severe pain of indeterminate origin and was treated by the chronic pain team with an array of medication. He also developed painful post-traumatic arthrosis of the ankle joint. After diagnostic injections it was though he would have some relief of pain if he had an ankle fusion as he was not keen on the idea of amputation. An ankle fusion was performed and went on to heal with good fusion albeit delayed. However he still was in significant pain and felt very disappointed that he did not get the pain relief that he was anticipating following the fusion procedure. He was now desperate for an amputation for pain relief. I was reluctant to operate on him for fear of leaving him with intractable causalgia and therefore sought the assistance of the rehabilitation team and the psychologists. After thorough examination and counselling, it was decided with the patient that an amputation would be of benefit to him. His family were also invited to participate in the decision making interview.

The limb requires to be marked and checked prior to prepping the limb or putting knife to skin . It needs to be crosschecked with the consent and again as part of the WHO check list to ensure that the most unfortunate ‘never’ event of amputating the wrong side is avoided! It is easy to see how marking can be masked by prepping in this fashion.

The scars of previous fasciotomy is an important consideration in deciding the creation of the long posterior flap which is my chosen method of fashioning the flap. In a non ischaemic amputation the posterior skin and soft tissues are better perfused due to the presence of gastrocnemius muscle perforators as also the vascular steal from other compartments and hence will lend themselves to harvest in a more biologically friendly manner. The thickness and overall quality of the skin over the stump also appears to be better ensuring a comfortable stump to fit a prosthesis on to.

Deciding the level of amputation is often the most challenging part of the operation . Too long a stump will result in difficulties with prosthetic fitting. Too short a stump will significantly reduce the length of the lever arm and result in an efficient system. Although there are prescribed lengths of stump that can be followed as a general algorithm, it is imperative that the level of amputation be decided by the operative surgeon based on clinical examination and investigations. This will ensure that the best perfused and distal level of amputation is chosen and will include the pain generator part of the limb for which the amputation is being carried out in accordance with the primary objectives of the operation.

It is generally recommended that the level of bone cut should be about 10 to 12 cm from the tibial tuberosity or 14-16 cm from the knee joint adjusted for limb length and patient height. These bony land marks should be marked on the limb and should be accurate in order to measure the distance accurately.
The horizontal skin incision should be at least 1 -1.5 cm distal to the bone cut. The fibular resection should be 3-4cm proximal to the tibial cut to avoid bony prominence on the lateral side of the stump which will inevitably cause problems with prosthetic fitting.

Next the long posterior skin flap is marked out.
I use the 1/3rd 2/3rd method of computing the length of the vertical and horizontal components of the skin incision to create the ideal flap length. The circumference of the limb at the level of bone cuts is first measured. 2/3rd of the circumference is the length of the horizontal part of the incision and 1/3rd of the circumference is the vertical length. If in doubt, generous additions to this length are used which can be trimmed back as required during closure.

Note that the medial vertical part of the incision is over the previous fasciotomy scar to ensure that devitalisation of a strip of skin does not occur and the scarred soft tissue is excised.

It is also important to check that the vertical limbs of the incision are symmetrically positioned and that the distal horizontal limb of the incision is perpendicular to the axis of the limb so that the flap margins are not skewed during closure.

I use a size 22 blade for the incision so that a greater length of cut can be made with each blade length . This ensures a more even cut. The lines drawn are carefully followed with the knife down to the deep fascia. It is important not to laminate the subcutaneous fat from the underlying fascia for fear of disrupting the perforator vessels and devitalising the flap.

The deep fascia is then divided in line with the incision.
Note that the lateral fasciotomy scar is far anterior to the lateral vertical limb and i would recommend that that there is at least a 2 cm width of skin to avoid the unfortunate complication of flap necrosis.

Sharp dissection of the muscles medial are carried out. if the saphenous vein is encountered distally this is ligated . Smaller vessels can be cauterised. The gastrosoleus complex is sharply divided at the distal end at this stage taking care to avoid cutting the posterior tibial neurovascular bundle.

On the medial side the posterior tibial nerve is identified and divided just above the level of the tibial cut. It should not be tractioned and after division is cauterised to avoid a stump neuroma.

The divided nerve is seen here after having been dissected free for the photograph.

Deeper dissection is carried out to isolate the posterior tibial artery which is transfixed and ligated just above the level of tibial cut. Smaller branches can be cauterised. There can be anomalous bifurcation or double vessel anomaly and therefore care must be taken to isolate both vessels.

The posterior tibial artery and vein being transfixed and ligated.

If need be cutting diathermy can be used to divide the muscle particularly in the non ischaemic limb as the muscle can be very vascular and can cause problems with a stump haematoma which may lead to infection and flap dehiscence. Too much diathermy is undesirable because of the thermal necrosis it will inevitably cause.

The incision is then deepened to the anterolateral compartment with sharp division of the peroneal and anterior tibial muscles at the level of tibial cut.

Anterior tibial and peroneal neurovascular bundles are located.

The anterior tibial neurovascular bundle seen here

The nerve is divided and cauterised and the vascular components are transfixed and ligated.

Similarly the peroneal neurovascular bundle is isolated and dealt with in the same fashion along with sharp division of the muscles circumferentially distal to the tibial cut.

A sharp periosteal elevator is used to denude both tibia and fibula of muscular attachments at the level of division. Note that the fibula should be resected 3-4 cm proximal to the tibia to avoid a bony prominence on the lateral aspect of the stump.

Having determined the level of tibial cut, I then divide the fibula 3 cm proximal to the proposed site of tibial cut. The reason for dividing the fibula first is that the leg becomes quite unstable if the tibia is cut first and therefore I do the fibular cut to start with. It also affords me good vision into the posterolateral aspect of the tibia at the level of the cut. The cut can be revised if need be after the tibial cut. The fibular cut should be aimed 45 degrees medial so that a short oblique cut results with no sharp edges pointing laterally which would again cause problems with the stump.

This now allows me to sharply elevate the gastrosoleal complex from the posterior aspect of the tibia with good vision

I still use a very old piece of kit for this part of the operation! The Blake’s amputation shield is an age old piece of kit that comes as two halves of a saucer shaped contraption with handles to lock them together. This allows me to lock it around the tibia to keep the proximal soft tissues completely protected during the process of tibial division. It can be used prior to fibular division too.

This instrument is very useful as prevents soft tissues from being traumatised and also protects against impregnation of the soft tissues with bone dust that can act as a nidus for heterotopic calcification. It is important that when an oscillating saw is used to divide the bones, continuous cold saline irrigation must be used to avoid the unfortunate problem of thermal osteonecrosis and the formation of a ring sequestrum.

The tibial cut is now completed and one can see the amount of bone dust that has splattered on to the amputation shield. Hence its use!

The final attachments of soft tissue are now dissected either by a periosteal elevator and scissors or diathermy (several small vessels are often encountered in this region) to release the amputated part of the limb.

The difference in the cuts between the tibia and the fibula are well appreciated in this photograph. The amputated limb is now carefully put into a limb bag and discarded into the incineration bin for disposal or histological analysis depending upon the indication for amputation.

The anterior cortex of the tibial crest is then bevelled at 45 degrees to avoid a sharp angle prominence below the skin when the stump is covered with the flap. This is done again with generous use of irrigation.

Sharp edges and spikes are rasped down and loose fragments of bone excised. Care should be taken not to damage the surrounding soft tissue with the rasp

I do use sterile bone wax to seal of the stump although this is somewhat contentious as opinion is divided as to whether one should use a foreign substance within a stump. I have personally not had a problem with its use. A small piece of wax is carefully spread over the distal end of the tibial stump and all excess is then carefully removed. This process is repeated for the fibular stump.

Remnant tags of muscle around the bone ends are carefully removed so as to have only the Gastrosoleus muscle now remaining in the flap

The plane between the Soleus and gastrocnemius muscles is then identified and the Soleus is dissected off the Gastrocnemius which lies posterior to the Soleus. This is often avascular but in cases of previous trauma or infection can be densely adherent or vascular as in this case. Hence judicious use of cutting diathermy is often helpful releasing the muscles from each other.

The proximal part is completed with the knife or sharp dissecting scissors. Some perforating vessels are again encountered proximally and will have to be cauterised.

This now leaves the Gastrocnemius as the only muscle in the posterior flap. I irrigate the wound with diluted iodine solution as is seen here.

This is often still too bulky and may require further thinning down until the posterior flap can be comfortably turned up and flexed over the stump.

The flap is then ready to be fashioned around the stump. It is important to excise any excess skin as it may make the final stump either bulbous or floppy with redundant skin otherwise. Any excessive skin must be trimmed back until it is a neat snug fit without too much pressure. It is also important to remember that flaps do retract and can do so to 70% of their original length. The deep fascia of the distal end of the stump is identified and dissected free for about a centimetre to be sutured to the deep fascia anterior to the distal tibial stump.

Prior to starting the first layer of sutures, I release the tourniquet to ensure that I have achieved haemostasis and cauterise any vessels that are bleeding. It is also useful to have stay sutures inserted at either end of the muscle aponeurosis so that a neat stitch sequence will ensue without crimping the layers. if need be the tourniquet can be re-inflated but if good haemostasis is achieved there is no need to do so.

Now the posterior aponeuroseal/ fascial layer is carefully sutured with interrupted sutures ( 1 Vicryl ) t the anterior fascial/periosteal layer. This needs to complete a myodoesis of the Gastrosoleus on t the tibia and must fit snugly. In this case the aponeurosis was densely adherent to the Gastrocnemius which also had to be debulked and hence bites were taken of the muscle just distal to the level of the stump to complete the repair. This muscle repair is extremely important as the muscle is a important component of the cushion that the stump requires in order to weight bear . Prolapse of the bone stump through this muscle cuff is highly undesirable as the stump will be very prominent under the skin making prosthetic fitting difficult and may even require a revision as a result if attention to detail is not paid.

Before closing the next layer I use a drain as a precaution to be taken out in 48 hours. This is usually the case in non ischaemic amputation where there can be troublesome oozing and I wish to avoid the tiresome complication of a stump haematoma which is one cause of infection. The drain is used in the free drainage mode for reasons that will become apparent in the next picture!

The other important step before closing the next layer is the installation of a perineural catheter (in this case an epidural catheter) in the vicinity of the tibial nerve. This is is connected to a continuous infusion pump which will administer Levobupivocaine 0.125mg/ml postoperatively for 5 days or so. This is an extremely important step to minimise postoperative pain especially phantom pain and has been shown to be very useful in the management of such pain post operatively. It is very important to place the drain as far away from this catheter and preferably in a sightly different plane to avoid the issue of the drain removing the local anaesthetic that is being administered. I have found the use of the perineural catheter to be invaluable in post amputation pain management and serves particularly to boost the confidence of the patient and improve his/her psychological state during a distressing time.

The deep fascia at the distal end of the posterior flap is identified and carefully apposed to the deep fascia dorsal to the stump. This is is very important as it defines the shape and trajectory of the skin sutures and eventually the shape of the stump after closure. Interrupted or continuous suture with 1 Vicryl can be used provided careful attention is paid to the the shape of the suture line.

Once completed, any dog ears or crimps in the suture line is debrided. It is my practice that if continuous suture is used then I would lock the running stitch every few throws so that even if one part of the suture gave way, the entire suture line does not unravel. A final assessment of haemostasis can also be made at this stage.

The final layer is that of the skin for which I use 2-0 Nylon. Start with both ends in an interrupted fashion so that the suture line can be defined clearly

Both vertical limbs can now be closed at the sides which then will indicate if there are any dog ears at the posterior end of these incision limbs

Dog ears are cumbersome and cannot be repaired with suture! They will almost always require careful excision to create a ‘v’ shaped defect which can be sutured in line with the rest of the incision. Over zealous excision should also be avoided so that the resulting skin defect does not become either too tight or loses its trajectory with the rest of the suture line resulting in a less then optimal aesthetic scar.

Inevitably the completed vertical line will show minor folding of the skin edges as a long limb is being sutured to a shorter suture line. However as long as there is no skin undermining and the edges are well apposed the folding does not matter. It is also important to ensure that the suture line is tension free as otherwise the suture line will necrose.

This process is also repeated on the medial side.

The completed suture line should be well apposed, free of tension or dog years and fit snugly over the stump without any loose or redundant skin which will make stump cover unstable, unwieldy and ugly!

I use Iodine impregnated paraffin dressings to cover the wound for their non-adhesiveness and antibacterial properties. If need be the skin suture line can be infiltrated with more local anaesthetic as this layer is the layer of pain!

Large absorbent dressing gauze or Amputation Gamgee is used both medial to lateral and dorsal to posterior to create a snug and well fitting absorbent cushioning for the stump and this is wrapped firmly with Crepe bandaging over orthopaedic wool applied in a figure of 8 fashion to avoid a tourniquet effect. Circumferential sticky tape should be avoided for the same reason.