Management of Bilateral Congenital Absence of the Fibula with Associated Abnormalities
THOMAS A. HAWKES, M.D., MAJ. MC DUANE G. MESSNER, M.D.
Agenesis of the flbula is the most common manifestation of a spectrum of dysplasias of the limbs28. The term congenital absence of the fibula is unpopular with most physicians because it has apparently become a wastebasket term for meromelias of any degree involving the fibula. Frantz and O'Rahilly suggested that anatomical terms be used for all congenital defects to ensure uniform classification30. Thus using their classification, terminal complete paraxial fibular hemimelia would be used to describe true congenital absence of the fibula and corresponding portion of the foot. The nomenclature of that classification has further been modified by the Committee on Prosthetics Research and Development whereby meromelia: Terminal, longitudinal, Fibular M: IV and V is used. The latter classification is based on a general-to-specific format citing absent skeletal elements. Capitalizing complete absence of the fibula puts more people in the ballpark, and further refinements can be made from there per the practitioner's choice.
Congenital absence of the fibula was first described by Goller in 1698. Classically the anomaly has complete or near-complete absence of the flbula, with these findings:
- There is gross shortening of the extremity with an average of at least 12.7 cm (5 in.) leg-length shortening with skeletal maturity. This shortening is most obvious below the knee, but it is present to a lesser extent in the femur as well. There appears to be a correlation in that the more deformed the foot the lesser involvement of the femur; and vice versa, if the rays of the foot are present the femur has more shortening.
- Anterior bowing of the tibia generally exceeds 30 degrees in untreated cases and is persistent if uncorrected. This bowing occurs at the level of the junction of the middle and distal thirds of the tibia and contributes to the gross shortening of the extremity. Medial bowing may be a further complicating factor.
- A skin dimple appears at the point of greatest angulation or the apex of the tibial bow.
- The foot exhibits marked talipes equinovalgus deformity (Figure 1 ).
- There is absence or fusion of the lateral metatarsal rays (Figure 2 and Figure 3 ).
Reported series by Frantz, Kruger, and Coventry show approximately 30 per cent of their cases bilaterally involved, with an incidence of associated abnormalities of 34.5 per cent involving either the hips or upper extremities. Generally, reported cases involve normal pregnancy with no familial incidence, no associated rubella. Conventry reported a case of twins with only one sibling involved, and Kruger reports normal progeny from an involved parent13,20. There is a preponderance toward the right side being involved more than the left. Theories of origin correspond to the sixth and seventh weeks of embryological formation with genetic versus teratogenic factors9,35. Duraiswami, in his classic paper on experimental causation of congenital skeletal defects, was able to reproduce the deformity consistently in chick embryos with insulin injection during critical periods of carbohydrate metabolism in progenitor cells15. Diet, radiation, and nitrogen mustards in the same time frame will produce similar defects33. Current research published in the birth defect series adds support to the credence of the theory of environmental insult to developing cells, though there may be genetic susceptibility factors.
Coventry and Johnson proposed a classification based upon extent of deformity in associated anomalies, with decreasing prognosis, function, and appearance for each type13. Type I has partial unilateral absence of the fibula, with minimum leg-length discrepancy, no bowing of the tibia, and no associated anomalies.
Shortening is the most common sign. in Type II the fibula is completely or almost completely absent. The involvement is unilateral. The classical deformity is present, with anterior bowing of the tibia, dimpling of the skin, equinovalgus of the foot, and absence or deformity of the rays and tarsal bones. There is always marked shortening of the extremity, and anatomical dissection reveals a fibro-cartilaginous-type band running from the proximal end of the tibia to the calcaneus (this is probably the underdeveloped fibular analog and a factor contributing to the deformity). Type III includes bilateral deformities (Figure 4 and Figure 5 ) or congenital absence of the fibula of Type I or Type II associated with other congenital deformities (Figure 6 and Figure 7 ). This was the largest group in Coventry's series, involving 55.2 per cent.
The treating physician is presented with basically a threefold problem: an angulated shortened tibia, foot deformity of an equinovalgus nature, and shortened, contracted soft tissues. Prior to 1950 patients were placed on the familiar orthopaedic ladder:
- Cast and manipulation
- Hardware, bracing, and shoe build-up
- Soft tissue procedures
- Bony procedures, tibial osteotomies, tarsal arthrodeses, and malleolar grafts
- Epiphyseal arrests and leg-lengthening procedures
- As a final resort, amputation.
The intended goals of equalized limb lengths and a suitable foot for weight-bearing were seldom achieved. Some patients were given a treatment boost to the amputation step, initially as an admission to failure, but later by choice because of uniformly good results. By 1965 the move to early amputation by Aitken, McCullough, Kruger, Wood2,25,23,36, and others for the unilateral deformity was complete, becoming the standard of treatment. On the other hand the bilateral case presented a treatment dilemma in that it was felt that amputation was seldom indicated when both fibulae are absent because the two legs in such cases are usually nearly equal in length, usually with functional knees. The good cosmesis, better proprioception and gait, proportional stump growth with the child who was relatively revision free, and the potential of end-bearing had been withheld. The following case is presented in support of the idea that the same benefits can be gained in the bilateral case.
R.S. is a white male born 4 September 1974. He was a term, uncomplicated pregnancy delivered vaginally. At birth he was noted to have (Figure 8 and Figure 9 ) bilaterally dislocated hips with bilateral meromelia; Terminal, longitudinal (Figure 10 and Figure 11 ) Fibular M VI, V, and left meromelia; terminal, longitudinal, Metacarpal V (Figure 12 ). Early treatment involved hip stabilization in an llfeld device. At age 6 months the left hip was well reduced, but the right hip remained dislocated. Bilateral iliopsoas tenotomies were performed, and both legs were placed in Crego skeletal traction for two weeks. The patient was placed in an Ilfeld splint, but the right hip remained poorly seated. At age 9 months an open reduction was performed on the right hip followed by six months of abduction functional splinting (Figure 13 ). Following satisfactory hip position at age 2, bilateral Syme amputations were performed at a two-week interval on the deformed feet (Figure 14 and Figure 15a ). Postoperatively the patient was treated in a rigid dressing (Figure 16 ). He was fitted with bilateral Syme prostheses and developed a bipedal gait without supports (Figure 17 ) three months post amputations. At 3 years 10 months the patient has just been fitted with his second pair of prostheses (Figure 18 , Figure 19 , and Figure 20 ). He is an independent ambulator, climbs stairs, runs, and participates in normal 3-year-old games and activities of daily living. He ambulates independently on his end-bearing stumps (Figure 21 , Figure 22 , and Figure 23 ) for demonstration purposes or for using the restroom at night, but he prefers the use of his bilateral prostheses.
The indications for early amputation have been stated as:
- Leg-length discrepancy of 7.5 cm (3 in.) or more, actual or predicted at skeletal maturity, or when the affected extremity is or will be 30 per cent or more shorter than the unaffected extremity utilizing Green-Anderson tables and growth-inhibition factors16,36.
- Foot deformity when a satisfactory weight-bearing surface is not provided, when conventional shoe wear is impossible and when cosmesis is undesirable.
- Psychological aspects in our society. The brace is equated to being a cripple, and shortness in stature is an oddity. What other children and parents will accept is unpredictable. A cosmetic prosthetic device arouses curiosity initially, but it is accepted by both patients and peers on a consistent basis. The excellent gait and cosmesis do not select patients out as "different" or as "an oddball." Family support is maximized by decreased hospitalization time, with an added fourth benefit of streamlined economies in number and length of hospitalizations.
The question of whether to do a Syme- or Boyd-type amputation preserving the distal tibial epiphysis appears as a dealer's choice (Figure 24 ). The Boyd type provides, in theory, additional length, eliminates potential migration of the fat pad, preserves septa and cushioning effect of the heel pad, and has less chance of disrupting the calcaneal artery, thus resulting in a dead flap. Both procedures prevent bony overgrowth of the tibia; the best results are obtained when the heel pad is aligned in a plantigrade fashion. The Syme technique remains the method of choice when the calcaneus is in marked equinus position (Figure 25 and Figure 26 ). In the series reported by Eilert no distinct advantage of one technique over the other could be defined16.
Kruger fitted bilateral patients with a stilt-type prosthesis with good results. Parents are reluctant to permit amputation of a fairly normal-appearing foot. They must be well informed as to the problems of leg-length discrepancies. The potential benefits psychologically and economically by early Syme or Boyd amputations for bilateral congenital absence of the fibula have been stressed (Figure 27 ). Multiple surgeries have been eliminated by preserving the distal tibial epiphysis. Early amputation enhances rapid mobility and psychological development of involved patients.
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