Evaluation Of Foot Conversions For Congenital Anomalies: Syme, Boyd, And Chopart
Virginia M. Badger, M.D.
In considering the surgical conversion of a deformed lower extremity to provide an amputation-type limb remnant, the level and type of amputation remain individual matters depending on the specific anomalies presenting.
The goals sought are the conversion of an anomalous limb into a stump which is more suitable for prosthetic fitting, provides increased comfort, and gives a better cosmetic result1,2,3,7,8.
It is the purpose of this paper to review the results of conversion surgery about the foot and ankle, i.e., use of the modified Syme's, Chopart, and Boyd operations, and to point out a few problems which still exist in the use of each of these procedures.
Types of Surgical Foot Conversions
Thirty-two patients with lower-limb deficiencies requiring conversion of the deformity have been reviewed. Of these patients, 31 had congenital anomalies and one sustained severe burns requiring amputation surgery. There are 26 patients with unilateral lower-extremity deformities and six with bilateral defects. Using the Frantz and O'Rahilly6 classification system for congenital limb deficiencies, foot defects were associated with various lower-extremity deformities as indicated in Table 1 .
The types of conversion surgery and number of feet involved were:
The modified Syme's(4) procedure consisting of ankle disarticulation without remodeling of the malleoli or disturbance of the distal tibial and fibular epiphyses, and utilization of the heel skin: 26 (17 right, 9 left).
The modified Boyd(5) procedure consisting of ankle fusion followed by forefoot amputation: 2 right.
The Chopart procedure consisting of disarticulation of the talonavicular and calcaneocuboid joints and preservation of the anterior tibial, toe extensor and peroneal tendons which were placed in the neck of the talus: 8 (5 right, 3 left).
Problems in Management
The average age of these 32 patients when they were first referred fell into two distinct groups: (1) those patients from 0-6 months of age-of whom there were ten, and (2) those of walking age, i.e., 1-6 years, 16 patients. Six were older than three years.
Since 1954, 36 conversion operations have been done on 32 patients (Table 2 ). Three postoperative complications have arisen and nine stump revisions have been necessary. These situations will be discussed in some detail, since recognition of the potential problems may reduce the number of revisions that are necessary.
The general plan of treatment followed the principles outlined by Aitken and Frantz3, namely, that of conservatism: "fit what presents, train and convert only if the functional result is unsatisfactory" (Fig. 1-4 ).
The age at which conversion was performed varied over a fairly wide range (Table 3 ).
At the clinical level bracing the foot deformity during the pre-school years is less costly, and brace-fitting problems are fewer than prosthetic-fitting problems during this period of rapid growth.
Postoperative Complications and Revisions
The three immediate postoperative complications encountered consisted of one patient with wound infection which healed with surgical drainage, antibiotic therapy and removal of a cartilaginous sequestrum; two patients who had partial skin slough anteriorly healed after revision of the skin flap. Revisions of the amputation stump were necessary in nine cases. In the Syme's-type stumps hypertrophic scar necessitated revision in two cases and spur formation in one patient 3 1/2 years after the original surgery accounted for a third revision. One Syme's stump required revision to a below-the-knee amputation. After knee fusion and additional unanticipated longitudinal growth, the converted limb was too long for above-knee prosthetic fitting (the original femoral defect was a short femur). Stump shortening to a long above-knee stump was necessary. Two Syme's-type stumps required revision because of incomplete excision of the calcaneus which by virtue of the remaining tendo-achilles attachment
rotated the heel flap posteriorly as illustrated in one bilateral and one unilateral case (Fig. 5 and 6 , and Fig. 7 ). The reason for the revisions was the rotation of the anterior scar into the weight-bearing area.
Three of the eight Chopart stumps have been reconverted to Syme's-type amputations; the heel-skin flap of one would not heal because of too much tension anteriorly, and on the patient with the burn scar a few areas of hypertrophic scar continued to break down anteriorly. One stump presently is painful anteriorly over the head of the talus because of the development of a slowly progressive equinus deformity and will need revision in the future.
The two Boyd-type conversions did not necessitate removal of the talus as Boyd originally described since in both cases a tarso-calcaneal coalition was present. Therefore, only the natural ankle joint was fused, the calcaneus positioned for better weight bearing and the forefoot ablated using the plantar skin to cover anteriorly. These stumps are very satisfactory for weight bearing but are somewhat bulbous. Hence, they constitute a more difficult fitting problem than do Syme's amputations (Fig. 8 and 9 and Fig. 10 ).
Amputation conversion has been done in three bilateral cases. In each case a different group of anomalies was present.
The first case involved conversion of bilateral complete longitudinal paraxial
fibular hemimelia to below-knee amputations. The end result has been quite satisfactory except for persistent mild genu valgus. However, this deformity is stable at present (Fig. 11 . Fig. 12 and 13 Fig. 14 and 15 ).
The second case involved bilateral partial paraxial tibial hemimelia with characteristic abnormalities of the bones of the feet and Polydactyly (Fig. 16 and 17 and Fig. 18 ). Syndactylism of the fingers with phalangeal abnormalities may also be noted in Fig. 16 and 17 . At the age of three years bilateral Chopart amputations were done after which the patient was fitted with a below-knee end-bearing PTB-type prosthesis on the left, and an end-bearing prosthesis with thigh corset and knee hinges on the right, both laced posteriorly (Fig. 19 and 20 ). During the child's years of rapid growth the mild varus of the right knee and the valgus on the left have been controlled by the use of knee hinges and thigh corset as illustrated in Fig. 21. The child's knees are stable, but there has been marked fibular overgrowth (Fig. 22 and Fig. 23 ). Range of motion of the knees is from full extension to 70 degrees flexion on the right and 80 degrees flexion on the left. Excision of the proximal fibulae is contemplated if function declines. The patient now wears prostheses without sidebars and corsets. These limbs are open posteriorly and are held in place by two posterior straps and an anterior supracondylar strap for decreased pistoning (Fig. 24-26 ). To date the dorsi-plantar flexion muscle balance at the ankle joint has been satisfactory and no equinus deformity has developed.
In the third bilateral case, the patient presented with bilateral proximal femoral focal deficiencies (Fig. 27 and 28 Fig. 29 and 30 ). She was managed conservatively and walked well with short-leg braces attached to shin pieces. The braces, which were articulated at the level of her ankles, were flexed for sitting, but locked for walking (Fig. 31 and 32 ). The patient objected to the length of her feet while sitting so bilateral Chopart amputations were done at the age of nine years (Fig. 33 and 34 Fig. 35 and Fig. 36 ). At present, she walks with above-knee, funnel-shaped, total-contact, end-bearing knee-disarticulation-type prostheses but is showing a degree of hindfoot equinus of one ankle which may require further surgical treatment in the future (Fig. 37 and 38 , Fig. 39 , and Fig. 39 ).
All three of these patients with bilateral amputation stumps are able to ambulate around the house without their prostheses and without external support. However, they cannot wear regular shoes to go outside which, in adult life, might be a major disadvantage. All are full daytime prosthetic wearers at the present time. Their ages are 11, 9, and 11 years, respectively.
The principles of surgical management of children with severe lower-extremity deformities is again emphasized:
"fit what presents,
convert only if the functional result is unsatisfactory."
The best period for surgical conversion is between the ages of four and six years when: (1) the surgical risk is minimized because of increased size, (2) the walking pattern can be established as easily with a brace as with a prosthesis and more economically, (3) a more accurate determination of the nature of the presenting cartilaginous anlagen can be made so as to develop a surgical plan most appropriate to the situation, and (4) the patient may be fitted with a prosthesis before starting school.
The Syme's-type stump is easily managed prosthetically. However, during the surgical procedure the entire calcaneus must be removed so that the tendo-achilles will not tend to pull the heel-flap skin into a plantarward position. Also, before the postoperative dressing is applied, it is advisable to stabilize the heel-flap skin with Kirschner wires or elastoplast to relieve any undue anterior heel-flap tension. In the unilateral cases the original bulbous stump remodels so that the malleoli, if present, become less prominent. Because of the relative difference in growth of the normal leg longitudinally and circumferentially in comparison to the deformed extremity, a satisfactory cosmetic effect can readily be achieved.
The Boyd-type stump has been satisfactory for weight bearing and has presented only mild prosthetic fitting problems because of the bulbous stump which does not remodel in the manner of the Syme's-type. This factor must be considered when a female patient is involved.
It must be stressed that conversion of the bilateral lower-extremity limb deficiencies to amputation stumps must be studied critically. In general, amputation is not recommended since the surgery may markedly compromise the ambulatory independence of these patients.
In the described treatment of cases I gratefully acknowledge the surgical care of Dr. George E. Scheer, Chief Surgeon, St. Louis Shriners Hospital Unit. Mr. Leo Tippy, certified orthotist, designed and constructed the prostheses illustrated.
Virginia M. Badger, M.D. is associated with the Shriners Hospital for Crippled Children St. Louis, Missouri
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