Chapter 17A - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles
The Syme Ankle Disarticulation: Surgical Procedures
F. William Wagner, Jr., M.D.
James Syme was a clinical professor of surgery at the University of Edinburgh from 1843 to 1869. He pioneered many innovative procedures in general surgery and was regarded as one of the premier surgeons of Europe and the United Kingdom. He is remembered today mainly for his disarticulation at the ankle joint. In 1842, he first performed the procedure on a 16-year-old boy for probable tuberculous caries of the talus and calcaneus. He reported the procedure in 1843. He performed approximately 60 to 70 more amputations of this sort in his lifetime. If one recognizes the many almost miraculous aids we now have in performing surgery, it is hard to realize that he did most of his work before the development of the science of bacteriology, antisepsis and antibiosis, blood transfusion, anesthesia, and all of the modern mechanical adjuncts to the actual surgical procedures. He listed three advantages over the transtibial level: "One, the risk to life will be smaller; Two, a more comfortable stump will be afforded; Three, the limb will be more seemly and useful for progressive motion." The final statement of his article cannot be said better today: ". . . on these grounds, I think amputation of the ankle joint may be advantageously introduced into the practice of surgery. I regret having cut off many limbs that might have been saved by it, and shall be glad if what has been here said in its favour encourages others to its performance."
Experience with many hundreds of cases at Los Angeles County University of Southern California (USC) Medical Center and Rancho Los Amigos Medical Center and in private practice has gone far to prove the value of his procedure. However, a review of the literature shows mixed acceptance by various authors in various centers. Alldredge and Thompson stated that it should never be performed in patients with diabetes, peripheral vascular disease, or neuropathic foot problems.
They believed that good results could be obtained in other patients with proper selection of cases and proper surgical techniques. Sarmiento and Warren reported 50% revision to a higher level in Syme ankle disarticulations in diabetic and dysvascular patients. McKeeverrelated satisfactory experience in a large series of military amputees. "For a male, the Syme amputation is the best possible amputation stump in the lower limb." Many authors report satisfactory experiences with the procedure and conclude that the residual limb is ideally suited for weight-bearing and lasts virtually the life of the patient when the procedure has been performed properly. There has been an occasional mention of aversion to the prosthesis in women. This has not been the major experience at Rancho Los Amigos Medical Center nor in private practice. Shel-swell concluded that the Syme ankle disarticulation should not be performed in a pulseless foot. There are a few references to its use in the dysvascular patient, but most of these are small series. Increased experience with revascularization procedures now permits its performance in previously nonoperable patients. Srinivasan reported 20 cases performed for Hansen's disease and pointed out that a Syme residual limb could last with proper care even in an insensitive foot. Level selection depends on vascular supply, condition of the heel pad, ability of the patient to use a prosthesis, and the absence of active infection at the operative site.
THE CLASSIC SYME ANKLE DISARTICULATION
Harris of Toronto has published two articles that describe the history, development, and technique of the Syme ankle disarticulation. Following trauma or in the case of congenital defects, some deviation in the flap may be indicated by the altered anatomy. Otherwise, no deviations are recommended.
The classic one-stage disarticulation is indicated in all circumstances when this level is the most distal effective amputation that will heal primarily. It is not indicated with local infection or with inadequate circulation, as indicated by skin perfusion tests, volume plethysmography, or the ischemic index as measured by Doppler ultrasound. For infection of the forefoot, the two-stage method is preferred. Trauma about the foot, congenital anomalies, tumors, and acquired deformities that are not suitable for procedures at the trans-metatarsal, Lisfranc, or Chopart levels are best treated at the Syme level. Since the modern Syme prostheses are relatively light, comfortable, durable, and cosmetically acceptable, this level is equally useful in men and women. With healthy plantar heel skin and the long lever arm of the virtually intact tibia and fibula, near-normal gait is possible. In recent years, the Syme level has gained popularity and is assuming a justifiably important place in amputation through the lower limb. Even in elderly diabetic patients, the durability of the operation has been demonstrated in finding that only 1 patient in 20 required revision when the Syme disarticulation was successful initially.
The incision (Fig 17A-1.) begins at the tips of the malleoli, goes up across the ankle joint, and then proceeds straight down across the sole. The anterior tendons are pulled down, divided, and allowed to retract. Arteries are transfixed and large veins ligated. Smaller vessels are electrocoagulated. Nerves are pulled down gently, divided, and allowed to retract. The medial and lateral collateral ligaments are divided at their insertion into the body of the talus to allow it to dislocate (Fig 17A-2.). Care must be taken on the medial side not to damage the posterior tibial nerve and artery. Syme, himself, recognized this problem after having severed the posterior tibial artery at the level of the ankle joint with resulting gangrene of most of the flap. Dissection of the os calcis is started subperiosteal on the dorsal and lateral surfaces (Fig 17A-3.). This allows gradual exposure of the flexor hallucis longus tendon, which is just lateral to the artery and nerves and aids in their protection. Subperiosteal dissection is continued medially to push the vital structures away from the body of the os calcis. Division of the Achilles tendon must be done carefully so that the posterior skin is not buttonholed. Continued stripping of the os calcis distally completes the removal of the foot. The tourniquet is released and hemostasis secured. Medial and lateral tendons are pulled down, divided, and allowed to retract. Opinion is divided as to the need to remove the plantar muscles. In this series, they have not been removed and are left in place. The only further dissection is for tissues that appear nonviable.
The malleoli and approximately 1 cm of the anteroposterior aspect of the tibia are exposed subperi-osteally. The tibia and fibula are transected at right angles to the long axis of the weight-bearing line (Fig 17A-4.). This provides a weight-bearing surface that is parallel to the floor. To obtain the broadest surface, the osteotomy is made so that the dome of the plafond is left with approximately 1.5 cm of cartilage. The greatest portion of the subchondral bone provides excellent weight transmission. The heel flap is now folded up into place for measurements, and the bones are palpated through the soft tissue. Any possible pressure points are smoothed with rongeurs and rasp. If the flap is too large, a full-thickness segment is removed from the distal edge. On rare occasions, bone must be removed to allow closure without tension. No attempts should be made to trim the dog-ears since the vascular supply to the flaps might be endangered. The dog-ears gradually regress and smooth down with casting and then with use of the prosthesis.
Migration of an imperfectly anchored flap has been reported in some series. Various methods have been devised for fixation such as skewering the flap with a Steinmann pin in the distal part of the tibia, adhesive taping, and immediate casting. We recommend suturing the flap to the tibia and fibula through drill holes (Fig 17A-5. and Fig 17A-6.). Inclusion of the plantar aponeurosis and the deep fascia in the tissues sutured provides excellent fixation. Subcutaneous tissue is closed with a few absorbable sutures. The skin is closed with nylon, polyethylene, polypropylene, wire, or similar nonabsorbable sutures (Fig 17A-7.). A moderate dead space is created and should usually be drained. Postsurgical hematoma is diluted and evacuated through a two-lumen tube (modified Shirley drain or modified Foley catheter) for 24 to 48 hours. Lactated Ringer's, Hart-man's or similar physiologic solution is used. Surgical dressings may be soft or rigid. We have found no advantage to immediate ambulation and have allowed 7 to 10 days' healing before applying a weight-bearing plaster.
THE TWO-STAGE PROCEDURE
The classic Syme ankle disarticulation frequently failed in dysvascular and infected patients. The superior function at the Syme level pushed the search for a method to allow its use in infected patients. Spittler et al. related their experience with Hulnick's two-stage procedure at Walter Reed Hospital. These patients had massively infected forefoot wounds from sharpened bamboo slivers that had been smeared with human excrement and placed in the ground during the Korean episode. These wounds were almost impossible to heal. Single-stage Syme ablations became infected in almost all cases. In the two-stage procedure, the infected forefoot was removed through disarticulation at the ankle. Virtually 100% of these patients healed, and the definitive amputation was performed 6 to 8 weeks later. Antibiotic prophylaxis is used preoperatively depending on bacterial cultures and sensitivity testing.
This technique was first adapted to the diabetic foot at the Los Angeles County General Hospital in 1954 and at Rancho Los Amigos Hospital in 1969. Experience, improvement in technique, and refinement of clinical indications gradually led to a 70% success rate. In 1970, a post-tourniquet reaction time was added. If the distal skin bled within 3 minutes, the healing rate was around 80%. In 1975, Doppler ultrasound was used to map blood flow, describe waveforms, and contrast the distal flow with the brachial artery flow. This led to the ischemic index, which was the distal pressure at several places in the lower limb divided by the brachial artery pressure. If the index was over 0.45, the success rate could approximate 90%.
The Syme ankle disarticulation performed in two stages is indicated in patients who have gangrene or infection of the forefoot, are not suitable for a transmeta-tarsal amputation, and have not responded to medical treatment or distal surgical care. The ischemic index should be 0.45 or higher in the diabetic and 0.35 in others. The patient should be a prosthetic candidate. The heel pad should be intact, and there should be no gross pus at the amputation site.
To allow slightly longer skin flaps to cover the malleoli, the incisions are started 1 to 1.5 cm distal and 1 to 1.5 cm anterior to the tips of the malleoli (Fig 17A-8.,A. The inferior incision courses directly down and across the sole and cuts all layers to the bone. The superior incision goes obliquely across the ankle joint. No tissue planes are dissected. The tendons are pulled down, cut off, and allowed to retract. The dorsalis pedis artery is ligated with a transfixing suture. The joint is entered across the dorsum of the talar neck. The medial and lateral collateral ligaments are divided, ultimately allowing the talus to be dislocated (Fig 17A-8.,B). Care must be taken not to cut blindly across the medial malleolus because the posterior tibial neurovascular bundle may be damaged at this point (Fig 17A-9.). Subperiosteal dissection is started on the superolateral surfaces of the os calcis. A bone hook is driven into the body of the talus for traction on the ligaments and control of the foot during dissection (Fig 17A-10.). Direct vision of the neurovascular bundle allows transection distal to the division into the medial and lateral plantar branches. Continued dissection distally allows medial retraction of the bundle and medial dissection of the os calcis. Care must be taken with the division of the Achilles tendon at its attachment to the os calcis, where it is virtually subcutaneous (Fig 17A-11.). Penetration of the skin has led to failure of the amputation even though the laceration was repaired. Division of the plantar aponeurosis and subperiosteal dissection of the os calcis medially complete the excision of the forefoot. The tourniquet is released at this point, and timing is started. Larger arterial bleeders are transfixed. Larger veins are ligated. Smaller vessels are coagulated. Bleeding is then assessed. If the most distal skin has not bled within 3 minutes, serious consideration should be given to going to the next higher level. If there is no bleeding in the flap distally at 5 minutes, then the Syme procedure should be abandoned and the amputation carried out at the transtibial level. A Shirley drain or Foley catheter is modified for irrigation and gravity drainage. Either the Shirley air filter or the Foley balloon tip is removed, and an intravenous tubing set is attached. The tip of the drainage tube is cut on a bevel. A forceps is pushed through the soft tissue under the posterior tibiofibular ligament and then out posterior along the fibula and through a stab wound approximately 10 cm above the ankle joint. The tube is then drawn into the cavity (Fig 17A-12.). Irrigation is started with 1 L of Ringer's lactate solution with 80 mg of gentamicin or similar aminoglycoside. Care must be taken not to exceed safe limits for ototoxicity and nephrotoxicity in these compromised patients. Irrigation is continued at approximately 1 L every 24 hours and is continued until the effluent is clear.
The heel pad is tested by folding it against the malleoli and plafond. If it is excessive in length, the skin and tissue should be removed until it closes with little or no tension. On occasion, the pad may shift medially or laterally due to a fascial band pressing one or the other of the malleoli. Division of the band and incision of the fat pad to provide a "nest" for the malleoli will hold the pad centered. Deep fascia over the anterior portion of the tibia and the remnants of the collateral ligaments are sutured to the deep fascia of the sole. A few subcutaneous sutures will level the skin edges. The skin is closed with nonabsorbable sutures or skin clips (Fig 17A-13.). A compression dressing of fluffs is contoured over the stump and wrapped in place with a bias-cut stockinette. Care must be taken not to fold the dog-ears upon themselves because circulation may be compromised.
Drainage is through gravity to a collecting bag, similar to a urine bag. Every 2 to 3 hours, the exit tube is clamped for 5 minutes to distend the cavity with irrigating fluid. Irrigation is continued for 48 to 72 hours, depending upon the degree of preoperative infection. The postoperative clinical course is also watched, and if there is fever or sign of local infection, the irrigation is continued. On occasion, this system has been left in place for 7 to 14 days. On removal, the tip is cut off aseptically and sent for culture and sensitivity studies. Systemic antibiotics are continued according to preoperative cultures for 1 week, unless the clinical course or late culture shows the presence of bacteria.
Upon removal of the tubing, the stump is wrapped in plaster. Care must be taken not to fold the dog-ears and create pressure areas. Two pieces of felt with holes protect the dog-ears. When the patient is clinically stable, crutch ambulation is allowed. Weight bearing is begun for those who have a firm heel pad, good skin turgor, and no sign of residual infection. Approximately 50% of the patients are weight bearing after the first stage while awaiting the second stage.
Healing is usually secure enough at 6 weeks to perform the definitive amputation. Occasionally, a week or more in a walking cast is needed. An occasional patient will be infected at the suture line and will require debridement along the suture line. Occasionally, there will be deeper involvement, and the malleoli must be removed to allow closure over a further irrigation system. In the very low percentage of patients who do not heal after the first stage, a transtibial amputation is performed.
Second-Stage Surgical Technique
Two elliptical incisions are made over the malleoli to remove the dog-ears (Fig 17A-14.). The amount of tissue removed should be equal to the volume of the malleolus. Care must be taken on the posteromedial aspect not to damage the posterior tibial nerve and artery. Close dissection around the medial malleolus will protect the neurovascular bundle. After subperiosteal dissection, the malleoli are cut flush with the joint surface (Fig 17A-15.). The fat pad is usually adherent to the central cartilage, which is left intact.
The malleoli are dissected subperiosteally to approximately 3 cm above the joint line. The medial and lateral flares of tibia and fibula are then removed parallel with the shaft (Fig 17A-16.). This leaves the anterior and posterior flares of the tibia and fibula for suspension and a moderate narrowing and flattening of the sides of the stump (Fig 17A-17.). Closure is adapted to anchor the pad to bone. The deep fascia of the sole is clamped with a towel clip to the periosteum of tibia, and the pad is tested. If it is too loose, soft tissue must be removed from the ellipses until the pad is tight. It is then sutured through two drill holes in the tibia and fibula, as well as to the periosteum. A few subcutaneous sutures level the skin. The skin is closed with nonabsorbable sutures. Soft dressings are used for a few days and then replaced with plaster (Fig 17A-18.).
On discharge from the hospital, the patients are usually independent in walking casts. They are observed in the outpatient clinic, and casts are changed at 2-week intervals. The warning is given to stop weight bearing and to return immediately if any pistoning should occur due to stump shrinkage. At about 8 weeks, the stump has matured, and the first prosthesis is fabricated. The plaster cast has been an invaluable aide inasmuch as it mobilizes the patient, aides in the muscular venous pump action of the leg, protects the healing wound, and controls and maintains apposition of the heel pad.
The Gait Laboratory, under the direction of Dr. Jac-quelin Perry, has performed function tests that show the Syme amputee to have greater stride length, faster cadence (Fig 17A-19.), greater velocity, and less oxygen consumption per meter traveled (Fig 17A-20.) than patients with more proximal amputations.
The Syme ankle disarticulation provides a long-lasting, durable residual limb, even in diabetic patients. The classic procedure, as described by Harris, remains the preferred procedure in cases without infection or dysvascular problems.
Revascularization of the distal portion of the limb in patients with arteriosclerosis has allowed performance of the Syme procedure in patients who would be faced with a higher-level amputation.
The two-stage technique has proved successful in patients with forefoot infections that preclude distal partial-foot procedures.
The Syme ankle disarticulation is actually a partial-foot ablation because of retention of the heel with its excellent weight-bearing characteristics. Function at the Syme level is superior to any other major amputation in the lower limb.
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Chapter 17A - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles