The main goal of all vascular surgeons in the field of arterial diseases or trauma in the extremities is arterial reconstruction in order to save vitality and function. However, despite substantial improvement of limb-salvage rates in patients with peripheral vascular disease, extremity amputation can be, in some cases, the only possible treatment for a limb severely affected by trauma, infection, tumour, or at the last stage of ischaemia .
Many vascular surgeons have traditionally viewed amputations in the treatment of an ischaemic patient as a failure to save the threatened extremity. Instead, amputation surgery should be considered as a very important part of the therapeutic armamentarium in the complex management of patients with limb-threatening disorders of the extremities. Extremity amputation can create enormous potential for the rehabilitation of many patients temporarily immobilized by vascular disease of their extremity.
In the context of surgical and endovascular procedures, extremity amputation has very often been viewed as a somewhat inferior management tool. This attitude can create:
• technical errors
• problems in stump healing
• a painful, functionally inappropriate stump (too long or too short) disabling mobilization
• problems with rehabilitation
• problems with proper prosthesis manufacturing.
From the tactical point of view, incorrect timing of the management steps is often encountered, thus causing failure and further devastation. The majority of patients involved are diabetics with signs of diabetic foot. Many surgeons indicate minor amputation for all cases of gangrene without taking any other steps into consideration. In my opinion it is imperative to follow these rules:
• First, manage the infection
• Then do the arterial reconstruction
• Finally, carry out minor amputation.
This is the so-called Vollmar IRA principle . The ratio of number of arterial reconstructions to number of major leg amputations due to occlusive disease can give quite precise information about the level of vascular disease management in a particular region or institution.
From the historical point of view, amputation is one of the oldest known surgical procedures. However, it was not until the mid sixteenth century that Ambroise Paré described the surgical techniques that are still in use today. Although often considered a destructive procedure, amputation, when appropriately performed, offers enormous potential for rehabilitation in most patients .
In general, the mortality associated with amputation depends not so much on the procedure itself as on the presence or absence of risk factors, especially cardiorespiratory insufficiency and cerebrovascular disease. The amputation rate in the USA is approximately 30 per 100,000 people per year but is 15-20 times higher among diabetic patients, who have an incidence of amputation of 600 per 100,000 [2, 3, 5]. Overall, more than 50,000-60,000 major limb amputations are estimated to be performed each year in the USA . In the United Kingdom, approximately 65,000 amputees are known to the Department of Health, with 6000 new patients being referred to limb-fitting centres annually [13, 18].
Causes of extremity amputation in occlusive disease or trauma include severe devastation of the extremity tissues and infection that has seriously destroyed those tissues and at the same time is life-threatening for the patient because of sepsis and toxaemia.
The timing of the procedure depends on the patient's clinical situation. In cases of serious tissue damage with an associated infection and sepsis, amputation can be considered as life-saving surgery, qualified as emergency amputation.
Patients with necroses and gangrene in extremities that have not been subjected to revascularization or those who have had more or less successful arterial revascular-ization and whose general condition is not threatening are indicated to an elective amputation (Table 9.1.1).
Emergency amputation in vascular patients due to occlusive disease or trauma has to be considered in cases of extensive tissue necroses, often with secondary infection causing wet gangrene or cellulitis presenting with massive putrid secretion, odour and general signs and symptoms of sepsis.
An infection can also be the primary cause of tissue destruction, especially where there is impaired perfusion (e.g. patients with diabetes or immunodeficiency states).
The basic therapy for all these patients is major emergency amputation with exact debridement. The term guillotine-like amputation is usually used; namely, a procedure without sutures of the stump or with only several stitches approaching the wound margins.
Complications of diabetes mellitus
Nondiabetic infection with ischaemia
Ischaemia without infection
After overcoming the infection a secondary closure can be performed. Acute or critical chronic ischaemia of an extremity, or severe trauma with extensive tissue loss or damage may, in some cases almost instantly, cause irreversible changes in tissues, thus hindering successful arterial reconstruction.
Moreover, in the cases mentioned above there is a serious risk of complicating ischaemic and reperfusion changes, threatening the patient's life.
In all these circumstances emergency major amputation is a life-saving procedure.
Revascularization of the lower extremity remains the treatment of choice for most patients with significant arterial occlusive disease. Redo vascular reconstructive procedures are also beneficial for limb salvage and for preserving ambulation ability. Unfortunately, in many patients, the continued progression of atherosclerosis obliterates all major distal vessels, eliminating the possibility of further reconstruction.
Vascular disease that is not reconstructable has become the most common indication for secondary amputation, accounting for nearly 60% of patients. Persistent infection, despite aggressive vascular reconstruction and appropriate treatment, is the second most common indication.
The goals of secondary amputation are:
• relief of ischaemic pain
• complete removal of diseased, infected and necrotic tissue
• achievement of complete healing
• construction of a stump suitable for ambulation with prosthesis.
The antecedent reconstructions do not worsen the condition of the leg and do not predispose the patient to a higher level of amputation. Therefore, initial attempts at vascular reconstruction are indicated.
Secondary amputation is indicated when vascular intervention is no longer possible or when the limb continues to deteriorate despite the presence of patent reconstruction . In a dysvascular patient, an elective amputation of the extremity may be considered because of chronic progressive ischaemia with rest pain and/or gangrene or necroses after one or more unsuccessful arterial reconstructions. Another indication may be the inability to improve perfusion because of an inappropriate out-flow tract.
Finally, patients with extreme destruction and/or necrosis of tissues causing extensive, profound or proximal damage (tarsal bones involved) are also candidates for elective amputation.
Primary amputation is defined as amputation of the isch-aemic lower extremity without an antecedent attempt at revascularization. Amputation is considered as a primary therapy only in selected cases.
The complete absence of detectable distal vessels using modern imaging techniques (magnetic resonance angiography, Duplex ultrasonography and high-resolution digital angiography), especially in the setting of advanced distal ischaemia associated with a low ankle/bra-chial blood pressure index (ABI) (<0.30), suggests that vascular reconstruction is not possible and that major amputation is inevitable. Such patients are best served by primary amputation.
Ulceration and necrosis of the weight-bearing surface of the foot and loss of the heel are frequent causes of primary amputation. Revascularization is useless for the preservation of ambulation in these cases. The use of myocutaneous free flaps does not yield a positive effect in the majority of cases.
Nonambulatory, bed-ridden elderly patients with severe occlusive disease associated with rest pain and tissue loss often with flexion contractures are not candidates for aggressive revascularization. They need only a stable, pain-free limb that can be used for positioning in bed or in a wheelchair and this is better enabled by primary amputation.
Other reasons for needing primary major amputation include multi-infarct dementia, immobility after serious brain infarctions, etc.
Finally, there are often physical as well as ethical contraindications to aggressive lower-extremity arterial reconstructions in patients with severe occlusive disease and terminal or near-terminal comorbid conditions. These patients require relief from pain and this calls for amputation  (Table 9.1.2).
The level of amputation is determined by a balance between the natural tendency to try to save as much as possible of the extremity and the surgeon's need to be sure that the amputation will heal at the chosen level.
The surgeon's goal is to avoid an inappropriately high level of amputation and revision of an amputation to a
Nonambulatory, immobile patient, without transfer capability, with limited cognitive ability, with ipsilateral limb contractures
No reconstructable arteries, uncontrolled pedal sepsis, progressive gangrene beyond mid-forefoot
Large heel ulcer with no possibility of plastic cover using a free flap
Life expectation of the patient less than 1 year, excessive risk of a revascularization because of high level of comorbidity, patient has been evaluated by a surgeon skilled in distal bypass surgery and reconstruction excluded as an option, life-threatening sepsis or haemorrhage
No venous conduit available, no skilled vascular surgeon available
From Durham JR (2000) Lower extremity amputation levels. In: Rutherford RB (ed) Vascular surgery, 5th edn, Vol 2. Saunders, Philadelphia, p 2185, with permission
From Durham JR (2000) Lower extremity amputation levels. In: Rutherford RB (ed) Vascular surgery, 5th edn, Vol 2. Saunders, Philadelphia, p 2185, with permission higher level. In practice, when clinical observation alone is used to choose the site of amputation, the resultant reamputation rate ranges from 15% to 40% [9, 15]. Clinical evaluation consists of detection of the most distal pulse level, skin viability, nutritional changes, physical signs of ischaemia and skin temperature. Although skin viability is the major factor influencing stump healing, clinical determination has little predictive value. Predicting the healing potential of forefoot amputation may be particularly difficult, even with noninvasive techniques [6, 9].
Many special investigative techniques and tests have been advocated for determination of the amputation level:
• Transcutaneous PO2 measurement
• Segmental Doppler blood pressures
• Laser Doppler flowmetry
• Segmental skin perfusion pressures
• Skin temperature measurements (thermography)
• Photoplethysmography and digital plethysmography
The most reliable noninvasive techniques are transcutaneous PO2 and measurement of skin clearance of [i33Xe], and less sensitive tools are segmental Doppler blood pressures and skin perfusion pressures.
220.127.116.11 Transcutaneous Oxygen Tension (PtCO2) Measurement
Transcutaneous oxygen tension (PtCO2) measurement should be taken with a skin sensor electrode heated to 45°C. It provides an accurate indication of the severity of ischaemia and predicts eventual healing success very well (blood oxygen contents depend on local blood flow). Successful healing has generally been reported if the local PtCO2 exceeds 40 mmHg and failure has always occurred at a PtCO2 of <20 mmHg [1, 7, 10, 15, 17].
It is possible to calculate local skin blood flow (at the proposed site of amputation) by the rate of clearance of an intracutaneous injected dose of [i33Xe]. Borderline skin blood flow by this method has been reported to be 2.6ml-100 g_1-min_1. Values above this border predict successful healing; values lower than 2.6 ml-100 g-1-min-1 predict healing only in 50% of cases [9, 11, 15].
The other techniques, namely laser Doppler flowm-etry, segmental blood pressure, skin temperature measurement, photoplethysmography and digital plethys-mography, do not have as high a predictive value as the techniques mentioned above.
Preoperative care and peri-procedural management involve treatment of the affected limb and the general condition and stabilization of the patient. It is necessary to treat infection intravenously with antibiotics and incision, debridement and drainage of abscesses and inflammation. Pain should be controlled adequately using strong analgesics. The prevention of large joint contractures is essential for achieving eventual rehabilitation and ambu-lation. A meticulous assessment of the patient's cardiorespiratory and renal systems is necessary. Even if urgent amputation is indicated, a period of 4-8 h for cardiac and metabolic stabilization is unavoidable. It is necessary to perform elective procedures with the patient's condition optimized. Also, the patient should be informed about the possible outcome of the amputation. This, coupled with a sensitive approach and rehabilitation, should moderate the emotional trauma and depression.
9.1.6 Surgical Techniques of Amputation
The most frequent types of extremity amputation are as follows:
• Lower extremity
• Minor amputations: toe amputation, ray amputation, transmetatarsal amputation, Syme's amputation.
• Major amputations: below-knee amputation, above-knee amputation (Fig. 9.1.1).
• Upper extremity
• Phalangectomy, ray amputation, amputation of the forearm, brachial amputation, arm disarticulation.
18.104.22.168 Toe Amputation
• A circular skin incision is made near the base of the toe.
The incision is brought through all tissue planes until the bone surface is scored circumferentially. It is necessary to strip the periosteum cephalad for a short distance, and then the phalanx is divided distal to the metatarsophalangeal joint using a bone cutter. After smoothing the edges of the bone, debridement of the wound, and excision of tendons and ligaments, it is necessary to decide on whether to close the skin or not (using interrupted monofilament sutures). This decision is made with regard to the presence or absence of infection and diabetes.
22.214.171.124 Ray Amputation
Tissue necrosis or infection extending to the metatarsophalangeal crease is an indication for ray amputation.
• A circular skin incision is made at the metatarsopha-langeal crease.
• The toe is amputated in the same way as described above.
• It is necessary to remove the remaining phalangeal bone with the use of a rongeur.
• Then the metatarsal head is freed from the attached tendons and ligaments and excised using a rongeur (Fig. 9.1.2).
• The ligaments and tendons will then be excised as proximally as possible.
• After irrigation, the wound may be closed using interrupted monofilament sutures in a vertical mattress technique.
• Ray amputation of the great toe requires a modified skin incision, with the amputation of the metatar-sal bone more proximally and a similar skin closure (Fig. 9.1.3).
Fig. 9.1.1 Possible levels for major amputations of the lower limb. (A Hip disarticulation, B-D above-knee amputation, B high-thigh, C mid-thigh, D low-thigh, E supracondylar amputation, F knee disarticulation, G below-knee amputation). From Malone JM (2004) Amputation in dysvascular patient. In: Hob-son RW, Wilson SE, Veith FJ (eds) Vascular surgery. Principles and practice, 3rd edn. Dekker, New York, p 557, with permission, 
126.96.36.199 Transmetatarsal Amputation
Indication for transmetatarsal amputation includes the situation in which gangrene extends slightly beyond the metatarsophalangeal crease.
In order to be able to create a reliable posterior flap the plantar skin must be viable.
• A slightly semi-arched incision is made on the dorsum of the foot 5-10 mm distal to the midpoint of the metatarsal shafts (Fig. 9.1.4). The incision is gently curved 90° tightly beyond the medial and lateral aspects of the foot.
• The incision is continued to the metatarsophalangeal crease and completed by extension across the plantar surface of the foot.
• The incision is carried down to the level of the metatarsal bones, dividing them slightly proximal to the skin incision using a bone cutter or oscillating saw.
• The bone edges are smoothed and the tendons and ligaments are divided as proximally as possible.
• It is necessary to trim the plantar flap sharply, preserving a thin layer of subcutaneous tissue.
• After stopping the bleeding the plantar flap is rotated dorsally, and interrupted absorbable sutures are used to close the subcutaneous layer.
• The skin is then closed with interrupted monofilament sutures applying the vertical mattress technique.
188.8.131.52 Syme's Amputation (Ankle Disarticulation)
This type of amputation has been advocated recently because of its satisfactory rehabilitation potential .
• A dorsal incision is made anterior to the ankle crease starting at a point distal to the lateral malleolus.
• The incision is then curved down and carried through the sole bilaterally to the calcaneus bone; the dorsal incision is brought down to the talus bone anterior to the ankle joint.
• Both posterior and anterior tibial arteries are ligated as necessary. The tendons are divided, permitting extreme plantar flexion of the foot.
After cutting both lateral and medial collateral ligaments the talus may be disarticulated. Then the calca-neus is isolated and excised.
The articular cartilage of the fibula and tibia are cut with a saw and smoothed with a bone file. Haemostasis is achieved and the heel pad rotated upwards.
The fascia is sutured to the deep fascia over the tibia. The skin is then closed using interrupted vertical mattress monofilament sutures, which can be left in place for several weeks.
Fig. 9.1.4a-c Transmetatarsal amputation. a Before amputation, b amputation line, c after amputation b c
Fig. 9.1.4a-c Transmetatarsal amputation. a Before amputation, b amputation line, c after amputation
184.108.40.206 Below-knee Amputation
• Preservation of the knee joint is extremely important for motion and transfer, even in immobile patients.
• Below-knee amputation is therefore advantageous compared with above-knee amputation.
• There are many ways to perform a below-knee amputation and, in my opinion, it is preferable to use the method of the long posterior myocutaneous flap.
• The ideal level of tibial bone transection must not be too distal. The optimal length of the tibial stump is as long as approximately 12 cm distal from the tibial tuberosity.
• An anterior skin incision is made about 1 cm distal from this level and should be continued bilaterally to a point 1 cm posterior to the edges of both bones (Fig. 9.1.5).
• Following this the incisions are angled and extended distally for a distance between one-third and one-half the circumference of the leg as measured at the level of the proximal incision.
• Another possibility for ensuring the correct length of the dorsal flap is to place the apex of the flap into the border between the middle and distal third of the leg.
• It is advisable to paint the dorsal flap before beginning the surgery. The right length of the dorsal flap is very important for the final success of the amputation.
• The greater and lesser saphenous veins are divided between silk ties, and the sural nerve is transected as high as possible to avoid painful neuromas of the stump.
• After dividing the anterior musculature it is necessary to identify the anterior neurovascular bundle and ligate these structures. The remaining muscles
are carefully divided from the bony attachments, the tibia is scored circumferentially and the periosteum is stripped cephalad.
The tibia bone is divided 2 cm proximal to the skin incision with the use of a pneumatic or hand saw.
The anterior edge of the tibia is then bevelled at a 45°
angle and the surface is made smooth.
The fibula is managed in the same manner but it is cut approximately 2 cm proximal to the level of tibia tran-
The posterior tibial and peroneal neurovascular bundles are divided. The remaining muscles are then divided using a large amputation knife. It is advisable to remove the soleus muscle in order to thin the posterior flap.
The wound is irrigated to remove all debris, haemo-stasis is achieved and after the placement of a suction drain the skin is closed with monofilament sutures, which are removed approximately 3 weeks after surgery (Fig. 9.1.6).
This type of amputation is indicated in patients who are not candidates for below-knee amputation because of ischaemia, infection and irreversibly damaged tissues, or in those whose general condition precludes rehabilitation and mobility. The way to determine the amputation level is mentioned above. Maximal femur length must be preserved, because it will lessen the energy expenditure required for ambulation and improve the chances for successful rehabilitation of the patient. There are three ways to perform above-knee amputation depending on the leg condition, arterial perfusion and tissue damage (see also Fig. 9.1.1): supracondylar amputation, mid-thigh amputation, high femoral amputation.
• A circumferential skin incision is made 2-3 cm distal to the site of division of the femur.
• The greater saphenous vein is divided and the anterior and medial muscle groups are cut using electro cautery or a large amputation knife.
• The superficial femoral artery and vein are suture ligated and the remaining musculature divided.
• The sciatic nerve is identified posteriorly, dissected free and suture ligated after gentle traction and shortening.
• The femur is then scored 2-3 cm proximal to the skin incision and the periosteum is stripped and transected.
The edges of the bone are then smoothed with a bone rasp.
Haemostasis is achieved, the wound is irrigated and after placement of a suction drain the skin is closed with monofilament sutures, which are removed approximately 3 weeks after surgery.
Although vascular problems in the upper extremities are substantially less frequent than in the lower extremities, occasionally there may arise a situation when a minor or major amputation is unavoidable. Most frequently, causes are irreparable vascular injury, chronic vascular disease (critical ischaemia especially in cases of multisegmental occlusive disease) or tumours. Acute ischaemia (inveterate or recurrent embolization from cardiac sources or thoracic-outlet syndrome) can also lead to irreparable changes and amputation. The ultimate goal of amputation surgery is to restore the maximal functional level of activity for the patient as quickly as possible .
• Amputations of the upper extremity are most easily performed with the patient positioned supine and their arm placed on the hand table. Either regional or general anaesthesia is satisfactory for these procedures.
• For determination of the level and technique we can apply the same rules as for leg amputations.
• Incisions used for these amputations should similarly create two flaps (shown in Fig. 9.1.7).
We can distinguish between digital amputation, ray amputation, wrist disarticulation, below-elbow and above-elbow amputation and shoulder disarticulation. Everything mentioned in this chapter regarding the perioperative management, rehabilitation and complications related to leg amputations also hold for upper-extremity amputations.
9.1.7 Postoperative Considerations and Rehabilitation
The most commonly used postoperative amputation dressing is the soft stump wrap. Gauze pads are applied to the wound followed by the gauze wrap and an elastic bandage. The amputation stump should be elevated to reduce swelling. It is necessary to hinder the flexion contractures after below-knee amputation using this type of wrap.
Amputation of an extremity is in itself a strong shock for every patient. Rehabilitation of a patient involves moderating his emotional trauma and depression as well as making an effort to enhance his maximal independence, mobility and ambulation.
Immediately after the patient is haemo dynamically stabilized, it is necessary to start respiratory physiotherapy and intensive exercise of the extremities that are not involved. Prevention of contractures is very important in the early postoperative period because it enables ambula-tion exercise in the next period.
The complications of amputation surgery may be divided into those that are specific to the operation and those that are due to severe cardiopulmonary disease and diabetes. Mortality rates following major amputation have been reported to be as high as 10% for below-knee and 40% for above-knee amputations [4, 9, 12]. The main cause of this enormous mortality is coronary artery disease and cere-brovascular disease, very often present in these polymorbid patients. The long-term survival prospects for diabetics are significantly worse than for nondiabetics. With recent improvements in patient preparation for surgery, anaesthetic techniques and intensive care, there should now be a mortality rate of less than 5% for below-knee and perhaps 10% for above-knee amputations .
The main complications of the procedure itself are infection and failure of stump healing due to ischaemia. Amputation level selection by objective tests can minimize postoperative healing failures. Small areas of wound breakdown will often heal with conservative management. Healing failure due to ischaemia with or without infection often requires revision. Haematomata formation can be prevented by meticulous intraoperative haemosta-sis and using suction drainage. Peri-operative antibiotic prophylaxis is appropriate for minimizing postoperative infection, which has been reported in 12-28% of major amputations. The most frequent late complication is phantom limb pain and disabling stump pain. Reported incidence of these complications is 5-30% . These pain syndromes develop more commonly in patients following amputation for trauma or prolonged ischaemia and are difficult to treat. To avoid them it is advisable to start with aggressive rehabilitation from the early postoperative period. Failure to rehabilitate should also be regarded as a complication.
1 Ameli FM, Byrne P, Provan JL (1989) Selection of amputation level and prediction of healing using transcutaneous tissue oxygen tension (PtcO2). J Cardiovasc Surg (Torino) 30:220-224
2 Berardi RS, Keonin Y (1978) Amputations in peripheral vascular occlusive disease. Am J Surg 135:231-234
3 Bild DE, Selby JV, Sinnock P, Browner WS, Braveman P, Showstack JA (1989) Lower-extremity amputation in people with diabetes. Epidemiology and prevention. Diabetes Care 12:24-31
4 Dietzek AM, Scher LA (1994) Lower extremity amputation. In: Clifford M, Sales MD, Goldsmith J, Veith FJ (eds) Handbook of vascular surgery. Quality Medical, St. Louis
5 Dietzek AM, Gupta SK, Kram HB, Wengerter KR, Veith FJ (1990) Limb loss with patent infra-inguinal bypasses. Eur J Vasc Surg 4:413-417
6 Goldsmith J, Sales CM, Veith FJ (1994) Surgical treatment of lower extremity ischaemia. In: Clifford M, Sales MD, Goldsmith J, Veith FJ (eds) Handbook of vascular surgery. Quality Medical, St. Louis
7 Katsamouris A, Brewster DC, Megerman J, Cina C, Darling RC, Abbott WM (1984) Transcutaneous oxygen tension in selection of amputation level. Am J Surg 147:510-517
8 Krupski WC (2000) Overview of extremity amputation. In: Rutherford RB (ed) Vascular surgery, 5th edn, Vol 2. Saun-ders, Philadelphia, pp 2175-2180
9 Malone JM (2004) Amputation in dysvascular patient. In: Hobson RW, Wilson SE, Veith FJ (eds) Vascular surgery. Principles and practice, 3rd edn. Dekker, New York, pp 555-573
10 Malone JM, Anderson GG, Lalka SG, Hagaman RM, Henry R, McIntyre KE, Bernhard VM (1987) Prospective comparison of noninvasive techniques for amputation level selection. Am J Surg 154:179-184
11 Moore WS, Henry RE, Malone JM, Daly MJ, Patton D, Childers SJ (1981) Prospective use of xenon Xe 133 clearance for amputation level selection. Arch Surg 116:86-88
12 Otteman MG, Stahlgren LH (1965) Evaluation of factors which influence mortality and morbidity following major lower extremity amputation for atherosclerosis. Surg Gyne-col Obstet 120:1217-1220
13 Sarin S, Sharmi S, Shields DA et al (1991) Selection of amputation level: a review. Eur J Vasc Surg 5:611
14 Seiler JG et al (1995) Upper extremity amputation. In: Ernst CB, Stanley JC (eds) Current therapy in vascular surgery, 3rd edn. Mosby, St. Louis, pp 680-685
15 TASC (2000) Management of peripheral arterial disease. Transatlantic inter-society consensus. Developed by TASC working group. Inter Angiol 19(1):[Suppl 1]1-310
16 Vollmar J (1982) Reconstructive surgery of arteries [in German]. Thieme, Stuttgart
17 Wyss CR, Robertson C, Love SJ, Harrington RM, Matsen FA 3rd (1987) Relationship between transcutaneous oxygen tension, ankle blood pressure, and clinical outcome of vascular surgery in diabetic and nondiabetic patients. Surgery 101:56-62
18 Yao JST (1988) Choice of amputation level. J Vasc Surg 8:544-545
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