Indications for Above Knee Amputation
Neoplasm– the tumors most associated with above knee amputation are soft-tissue sarcoma and Ewings tumor.
Trauma
Vascular insufficiency
Revision of lower site amputation due to non-healing or ill-fitting limb prosthesis
Surgical Details of Procedure
1. In above knee amputation the skin is incised using a No. 10. blade along the previously marked lines guiding the creation of the skin flaps
2. The amount of bleeding from the skin is noted to insure good vascularization of the flaps
3. The scalpel is used to cut through the subcutaneous tissue to the level of the muscle.
4. Bleeding vessels are controlled with hemostats and then ligated with 3-0 or 4-0 silk rather than Bovie cautery to minimize tissue damage.
5. Care must be taken to locate the greater saphenous vein on the medial aspect of the thigh superficial to the muscle layers. This is cross-clamped, tied with 2-0 sutures and cut with a Metzenbaum scissors.
6. An incision is then made into the lateral muscle layers of the thigh to avoid the major vessels of the leg which lie on the medial side of the femur.
7. The level of the muscle incision should be slightly more cephalad (toward the head) than the skin and subcutaneous muscles to allow proper fashioning of the soft tissue flap.
8. Generally, in above knee amputation the muscles on the lateral thigh are severed down to the level of the femur.
9. The muscle incision is then taken circumferentially around the leg with care taken to palpate for the femoral artery and vein (many general surgeons do not use a thigh tourniquet and injury to these vessels can cause significant hemorrhage.
10. These structures are located and dissected free and cross-clamped.
11. In above knee amputation, the artery is usually doubly ligated with a stick-tie of 2-0 silk on the cephalad border and then incised.
12. The vein is also cross-clamped and doubly ligated.
13. The sciatica nerve is located by inspecting the area posterior to the ligated femoral vessels.
14. The nerve is isolated from the surrounding tissue using blunt dissection.
15. To minimize the formation of an amputation sciatic neuroma in above knee amputation the nerve is pulled down into the wound as much as possible and a large straight Ochsner clamp is applied to nerve as cephalad as possible.
16. A second crushing clamp is applied just distal to the Ochsner clamp.
17. The initially placed proximal clamp is removed and the area is ligated with a 0 silk suture.
18. It must be noted that fine ligatures or absorbable ligatures should not be used as these can result in formation of stump neuromas .
19. The crushed portion is not ligated but serves as a “roughened area” to prevent slippage of the heavy silk ligature.
20. The nerve is then allowed to retract up into the proximal part of the incision. If the nerve has been controlled properly it should retract up into the would and largely out of view.
21. Inspection is performed to locate the profunda femoris artery and vein in the posterior muscle group if this has not already been accomplished.
22. These vessels are then doubly ligated and incised to lessen the risk of hemorrhage post above knee amputation.
23. A circumferential incision is then made in the periosteum at the planned level of bone resection with a knife.
24. A perisoteal elevator is used to to push the periosteum distally for several centimeters.
25. A bone saw is used to transect the bone. If a hand-held gigli saw is used the bone is transected from the posterior to the anterior. If an electric saw is used the bone is transected anterior to posterior.
Gigli saw used in amputation
26. Generally if the gigli saw is used approximately three-fourths of the way through the angle of the transection it is slanted somewhat cephalad (toward the head) to slightly bevel the anterior bone edge.
27. As the bone is being transected, the area is lubricated with water from a bulb syringe.
28. The transected lower limb is removed from the field of operation.
29. The sharp edges of the bone are rounded and smoothed off with a rongeur.
30. The muscle and skin are then inspected for bleeding and controlled with a hemostat and ligated with silk sutures.
31. The entire wound is irrigated with warm saline to wash away bone chips and to visualize the site in preparation for flap closure.
32. The anterior and posterior edges of the deep fascia closest to the bone is reapproximated over the bone edge with interrupted large absorbablye sutures.
33. As this layer is being closed it is common for a flat Jackson Pratt drain to be placed and brought out through the skin via a lateral thigh stab wound.
34. The more superficial layers are then reapproximated with interrupted absorbable sutures. As the flaps are being closed any excess muscle and tissue is excised.
35. The assistant then encircles the stump with their hands and the subcutaneous tissue and skin is closed with interrupted sutures.
36. in above knee amputation The skin is usually closed with interrupted nylon sutures or surgical staples.
37. The effect of closing the flaps is one of sewing together the upper and lower lips of a fish’s mouth.
38. To conclude above knee amputation, the stump is covered with fluffs of sterile gauze and wrapped snuggly but not overly firmly in an ACE dressing.