Above- and Below-Knee Amputation




Historical Background


The first recorded instance of amputations and prosthetic replacement appears in the Rig-Veda, written in Sanskrit between 3500 and 1800 bc . The ancient Greek text, “On Joints,” written in the latter half of the fifth century bc , recommends amputation for gangrene below the “boundaries of blackening” as soon as it is “fairly dead and lost its sensibility.” In the first century, Celsus described circumferential compression above the operative site, the technique of amputation through healthy tissue, and the ligation of vessels. Over the ensuing centuries, there was a return to the use of cautery to prevent hemorrhage with ligation reintroduced by Paré in the sixteenth century. The development of the Morel tourniquet in 1674 led to control of hemorrhage so that attention could be directed to the operative site. Because of a necessity for speed, amputation was initially performed in one cut, as a “classic circular cut,” with detachment of skin, muscles, and bone at the same level. In 1718 Petit promoted a “two-stage circular cut” to reduce suture line tension, with initial transection the skin followed by the muscles and bone more proximally. During the seventeenth and early eighteenth centuries, Lowdham, Verduyn, and Langenbeck introduced the concept of a “flap amputation” with use of a soft-tissue flap to cover the bone without tension.




Indications


The level of the amputation is selected based on the capacity for the surgical site to heal and the ambulatory potential of the patient. There is a substantially lower energy requirement for ambulation and commensurate greater likelihood to ambulate with a below-knee amputation. Thus even in the presence of marginal circulation, a below-knee amputation may be attempted. When the foot is severely infected, active cellulitis should be brought under control before performing the amputation. If necrosis and infection are severe, a guillotine amputation, 2 to 3 cm above the ankle, should be performed to remove the septic source. Several days later, a more definitive below-knee amputation is performed, with the area of the guillotine amputation carefully excluded from the operative field. Above-knee amputations are typically performed at the supracondylar level. Rarely, if the line of temperature demarcation is at the knee or higher, a midthigh or high-thigh amputation may be required.




Preoperative Preparation





  • Evaluation of cardiac and pulmonary status is necessary to optimize perioperative course and rehabilitation.



  • Optimal nutritional status is essential for stump healing.



  • Anesthesia may be general or regional based on preference and needs.



  • Prophylactic antibiotics reduce perioperative wound infection rates.



  • Venous thromboembolism prophylaxis is mandatory.



  • Preoperative physiotherapy may help prevent flexion contracture.





Pitfalls and Danger Points





  • Inappropriate stump length



  • Stump trauma because of shear injury to the skin, subcutaneous tissue, and deep tissue



  • Stump trauma because of pressure-induced necrosis from the underlying bony structure



  • Stump trauma because of a tourniquet-type dressing



  • Flexion contracture of the hip in above-knee amputations or the knee in below-knee amputations





Operative Strategy


The basis of selection of amputation level depends on the indication for the amputation, potential for rehabilitation after the amputation, and presence of an adequate blood supply as assessed by physical examination and vascular laboratory studies. Although not commonly performed, other studies that have been used to assess adequate perfusion include intradermal isotope blood flow measurement, skin perfusion pressure, skin fluorescence, and transcutaneous oxygen measurements. An above-knee amputation is often performed as a final level of amputation after a previous failed below-knee amputation but may be the initial amputation appropriate for patients who are unlikely to be ambulatory or those with severe ischemia or infection that precludes healing of a below-knee amputation.




Operative Technique for a Long Posterior Flap Below-Knee Amputation


Skin Incision


The most common technique for a below-knee amputation uses a long posterior flap. The tibia should be divided 10 to 12 cm or approximately four fingerbreadths distal to the tibial tuberosity, but functional stumps may be achieved with as little as 5 cm of residual tibia ( Fig. 51-1 ). The anterior skin incision extends two thirds of the circumference of the leg. A thicker posterior flap results in more prominent “dog ears” but may be better vascularized. The length of the posterior flap is approximately one third the circumference of the leg and should be gently curved to reduce dog ears. After venous exsanguination and application of the pneumatic thigh-high tourniquet, the skin and fascia are incised together beginning with the transverse component and then extending to complete the posterior flap. The anterior and lateral compartment muscles are divided.




Figure 51-1


Incision and steps in the creation and closure of the posterior flap of a below-knee amputation. Note the transected tibia and fibula. A, The skin incision is usually placed approximately 10-12 cm distal to the tibial tuberosity. The length of the anterior transverse skin incision is approximately two-thirds of the circumference of the extremity at the site of amputation with the length of the posterior skin flap approximately one third the circumference of the extremity. B, The fibula is transected 1-2 cm proximal to the tibia. C, The soleus muscle, which derives its primary blood supply from the peroneal artery, may be resected to create a thinner posterior flap. The gastocnemius muscle is usually supplied by arterial branches arising directly from the popliteal artery and is usually well vascularized. D, The fascia is closed with interrupted absorbable sutures. E, The posterior flap should be free of tension. It is unnecessary to remove “dog ears” at the ends of the incision because the stump will rapidly remodel in a short time.

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Mar 13, 2019 | Posted by in VASCULAR SURGERY | Comments Off on Above- and Below-Knee Amputation
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