24 - syme's amputation 2

The ankle Syme amputation, first introduced by James Syme in 1842, has been an underutilized surgical procedure despite its advantages over the below-the-knee amputation. This procedure has been avoided primarily due to the misconception of technical difficulty. This article, in describing patient selection and surgical technique, will dispel this misconception while highlighting the advantages of the ankle Syme amputation over more traditional below-the-knee amputation. What is the Ankle Syme Procedure? The ankle Syme procedure is classically described as amputation of the foot at the ankle joint with retention of the plantar heel that is re-approximated anteriorly. Surgeons may take a one- or two-step approach. The single approach, which is most commonly performed, entails removal of the lateral and medial malleoli before closure. The two-step approach disarticulates the foot at the ankle joint but leaves the malleoli to be removed during a second surgery – usually, 6 weeks later. The two-step approach may be desirable with severe infection, and in allowing for demarcation of the viable and non-viable tissue. Indications and Contraindications The ankle Syme procedure has historically been reserved for patients with congenital deformities, such as femoral hemimelia, soft tissue and osseous sarcomas of the foot and traumatic crush injuries sustained by otherwise young healthy patients. This procedure has also recently been utilized in the treatment of ischemia, diabetic non-healing ulcerations and osteomyelitis. Patient's foor prior to ankle Syme amputation. Patient had a previous gunshot wound to his leg resulting in a traumatic cavovarus foot with chronic ulcerations and infections. The absence of a viable, intact heel pad is the primary contraindication of an ankle Syme amputation. More proximally extending osteomyelitis is also a contraindication to ankle-level amputations. Radiographs should be obtained prior to surgery to rule out osteomyelitis extending into the tibia, fibula or talus. As with all amputations, wound healing capabilities are important to note before performing surgery. Dikaut et al. (1), later modified by Pinzur (2,3), outlined parameters to predict if patients have the nutritional status, immunocompetence and arterial flow to heal the amputation. Patients who do not meet a minimal serum albumin of greater than 3.5 gm/dl, total lymphocyte count of greater than 1500 and ABI of greater than 0.5 have poor surgical outcomes usually resulting in more proximal amputations. Ankle amputations also have little benefit for wheelchair-bound patients as they are already non-ambulatory and salvage of the lower leg will be cumbersome. Incision placement for the ankle Syme amputation. Surgical Technique The patient is positioned in the supine position under general or regional anesthesia – a thigh tourniquet may be used. The incision site may be drawn anteriorly by a line placed 1.5 cm anterior and inferior to the midpoint of both the medial and lateral malleoli. The plantar incision is made 90 degrees from the anterior cut. The plantar cut should be made at the level of the calcaneal cuboid joint or more distal. It is always better to err on the side of caution to ensure adequate length of the plantar flap. Controlled depth incision with vessel ligation. The incision is made first in a controlled depth fashion. Nerves, veins and tendons are identified, sharply dissected and allowed to migrate distally. The distal foot may be sharply transected at Choparts joint for better visualization of the talus and calcaneus. The ankle joint is then incised anteriorly revealing the talar dome. Plantargrade force is applied to the talus with a bone hook. Great care must be taken while dissecting the medial collateral ligaments to preserve the posterior tibial artery. Blunt dissection of the medial neurovascular bundle is performed between the flexor hallucis longus and flexor digitorum longus tendons. Preservation of the artery at its maximum length is essential, as it is the sole blood supply to the plantar flap and the most critical point of the operation as described by Syme. Excision of the talus with a bone hook. Preservation of the posterior tibial artery is crucial during this step. Once the talus is removed, attention is directed at removal of the calcaneus. A bone hook, pulling the calcaneus anterior and plantarly, combined with both sharp and blunt dissection aid in avoiding the second pitfall of an ankle Syme amputation. Little skin lies posterior to the plantar fascia. Penetration or “button holing” this skin while trying to detach the plantar fascia from its calcaneal attachment will doom the procedure as the stump will not heal after this type of injury. The tibial and fibular malleoli are then resected at the level of the plafond and parallel to the weight-bearing surface. Some surgeons prefer to resect the articular cartilage, as it ensures better adherence of the tibia to the plantar fat pad. If infection spread is a concern, the cartilage should be left intact. The wound should then be irrigated under pulse lavage. Skin closure with a closed suction drain. The dog ears will remodel with the aid of a stump shrinker. Before closing, three drill holes are made through the anterior tibial plafond. The plantar fat pad is secured to the anterior tibia through the drill holes with a non-absorbable material such as #2 Fiber Wire. This prevents migration of the fat pad at the end of the osseous stump. Debulking of residual tissue may be necessary for re-approximation. Closure is done over a suction drain that is introduced through a more proximal stab incision. The stump is placed in a Jones compression dressing with non-weightbearing status until the wound has completely healed. The drain is removed in 24 to 48 hours and the sutures are removed in three weeks at which time the patient is fitted with a stump shrinker – this helps to remodel any “dog ears” that might be present and permits proper fitting of the prosthesis. Application of a post-operative compressive dressing. Complications The ankle Syme amputation is a salvage procedure that leaves patients with far better ambulatory abilities than with below-the-knee amputation; however, there are five major complications of the ankle Syme amputation, according to Brodsky (4). The most common complication is early failure of the wound to heal. For this reason, post-operative vascular assessment, careful dissection around the posterior tibial artery and visualization of actively bleeding wound edges after disarticulation of the ankle are chief in optimizing patient outcomes. Migration of the stump is another complication that can cause poor fit and function of the prosthesis. This complication usually can be avoided by suturing the plantar fascia to the distal tibia. While the ankle Syme amputation has the advantage of being covered with the plantar skin and fat pad, making it thicker and better at withstanding pressure from weight bearing than other amputations, ulcerations may still occur. Ulceration of the distal stump is most commonly seen in diabetics, usually caused by pressure from the distal fibula. Fourth, painful nerve stumps can be treated by surgical excision or burying of neuroma formations. And finally, patients may be disappointed with cosmetic results; however, patients usually choose function over poor cosmesis. The ankle Syme amputation, while initially thought to be useful in treating only congenital deformities and traumatic injuries, has been proven effective in patients with diabetes, infection and vascular insufficiencies. Special attention should be given to minimum nutritional and vascular requirements prior to surgery to ensure successful healing. The procedure itself is not technically difficult, but does require more skill than the below-the-knee amputation. Post-surgical results of an ankle Syme amputation far outweigh those of the below-the-knee amputation, resulting in lower energy cost with ambulation, higher velocity gait and a longer stride length (5). Shorter rehabilitation time and overall cosmesis are also contributory in overall patient satisfaction. While this procedure is not indicated for all patients, an ankle Syme amputation is an effective surgery that should be offered to appropriate candidates.