Fibular Hemimelia with Tibial Angulation: The Identification of a Problem
JAMES M. CARY, M.D.
Observation of patients in whom Type II fibular hemimelia with significant bowing of the tibia has been treated by simple ankle disarticulation and prosthetic fitting has demonstrated, as the patient grows to maturity, that the amputation stump so produced is less than optimal. Deformity of the stump, hypoplasia, and poor transmission of prosthetic forces have led to skin complications and difficulties with prosthetic fit and alignment. A pilot case, in which the angulation was corrected by osteotomy at the time of conversion, shows promise of retaining improved stump alignment and effectiveness with growth.
In those cases of the congenital limb deficiency, fibular hemimelia, in which an eventual shortening in excess of 10 cm is expected, most centers accept conversion and prosthetic fitting as the most practical form of treatment4,8. In further classifying this anomaly Coventry and Johnson described a kyphotic deformity of the tibia, usually associated with absence of lateral rays of the foot and severe equinovalgus contracture, which they termed Type II 2 .
A certain degree of anterior and medial bowing is present in most cases of fibular hemimelia. In many cases the bowing is modest in degree; and simple conversion, either by Syme ankle disarticulation or by Boyd calcaneo-tibial synostosis, may be expected to provide satisfactory function. There is, however, a group of patients in this Type II variety in whom the amount of bowing exceeds 30 degrees. In these patients we have observed, by surveillance through the course of growth and maturity, increasing problems with prosthetic fit, comfort, and function.
Case Report 1
J. M. was admitted in 1958 at the age of 4 months for treatment of left fibular hemimelia. Initial examination demonstrated complete absence of the fibula, and a tibia that was 4.5 cm shorter than the opposite side and sharply angulated 45 degrees in its medial third with the apex anterior and medial. The foot was in extreme equinovalgus position and lacked the lateral two rays ( Figure 1 ).
Initial treatment was ankle disarticulation by the Syme technique. Healing was uneventful. The patient was fitted at the age of I year with a hard-socket below-knee prosthesis equipped with hinges and thigh lacer and with toddler harness suspension.
Initially he had little difficulty in ambulation, and the deformity of the stump was easily fitted by prosthetic modification. Several episodes of redness and skin irritation over the angulation are recorded in his record, but these responded to prosthetic adjustment. At the age of 5, however, a recurring pressure sore developed over the apex of the sharply angulated tibial stump despite attempts at modification of the prosthesis. After skin healing, an attempt was made to reduce the bony prominence by tangential resection of bone across the prominent apex of the tibial kyphos. Apparently his surgeons were reluctant to perform a transverse corrective osteotomy lest nonunion develop.
The procedure allowed refitting with a PTB prosthesis, again with hinges and thigh corset. Fit and alignment were apparently critical, and from time to time skin irritation and imminent breakdown required periods of rest out of the prosthesis, with frequent refitting and reshaping of the socket.
At age 13 these problems induced a critical examination of the patient's prosthetic gait mechanics. A valgus thrust on the knee during stance phase produced an asymmetry of gait characterized by short stride and lack of stable pushoff on the prosthetic limb. A 20-degree genu valgum of the stump was present. This deviation was incompletely compensated in gait even by inset alignment of the prosthetic foot ( Figure 2 ).
In 1972, at the age of 13 and 1/2 years, a stapling of the medial side of the distal femoral epiphysis was carried out in an effort to realign the stump for more appropriate mechanics.
Correction of the valgus deformity took place over a period of 12 months thereafter, allowing improved alignment of the prosthesis and a significant improvement in the patient's gait.
Some 16 months after this procedure the patient fell sharply, flexing and twisting the left knee beneath him. When examined he demonstrated findings characteristic of internal derangement. Arthrotomy and excision of the medial meniscus were combined with removal of the staples from the medial epiphyseal line.
Since that time the patient has had no major problems but is still committed to the support of hinges and thigh corset for stability. Increased activity has frequently resulted in redness and tenderness of the skin of the stump in the anterior condylar region and along the anterior aspect of the left shin. The stump at full growth is quite slender, moderately angulated, and shows little endbearing use. Most of the pressure from the prosthetic socket is transmitted to the anterior condyle and patellar-tendon area. The stump is poorly muscled, and the entire bone is slender and hypoplastic when compared with that of other patients who, with less angulation, have retained the endhearing capacity and fit of the uncomplicated Syme stump ( Figure 3 ).
If conversion and prosthetic fitting are felt to constitute the alternative of choice in the treatment of a serious limb deficiency, the goal for the surgeon is to fashion a stump which is functional not only for the immediate needs of the small child, but which will retain its effectiveness throughout the course of proportionate longitudinal bone growth. The cases of fibular hemimelia in which kyphosis of the tibia exceeds 30 degrees seem to provide a less-than-adequate amputation stump and prosthetic fitting as they approach maturity. R. Mazet5, in reporting on Syme amputations, states, "After amputation the kyphotic tibia gradually becomes straighter." This may be true for the milder grades of angulation, but we have not observed it in the more severe deformity.
Thompson, Straub, and Arnold7 in 1957 advocated resection of the fibrous anlage of the fibula together with tendon lengthenings for accurate repositioning of the foot, feeling that this would, with growth, correct the angulation. In several well-documented cases presented in their article, correction of the angulation did, indeed, occur. It is to be noted, however, that this transpired in the presence of a well-corrected and active foot. They make oblique reference to the value of correction of the angulation for the amputee, noting that many patients requested amputation at, or near, maturity. They stated that if the stump was straight and good heel skin had been saved, endbearing was possible.
In several of our older cases in which resection of the fibular anlage was carried out in conjunction with ankle disarticulation, little, if any, change in the angulation of the tibia has resulted with growth.
Absence of endbearing function in prosthetic use in the young, growing child seems to lead to a length discrepancy that is greater than would be expected with proportional growth of the anomalous tibia. Thinning of the cortex and hypoplasia of the bone are evident on X-ray. There is less muscular development and firmness of the stump than in those patients for whom endbearing fitting has been obtained.
It has been the practice in this clinic to avoid diaphyseal amputation in the growing child if there is any other alternative. The complications of overgrowth and of attenuation of the stump are well known. Two of our patients were initially treated elsewhere with diaphyseal amputation of the tibia at the level of the sharply angulated kyphos. One of these patients was revised to knee disarticulation near maturity because of severe stump problems and inadequacy of prosthetic function. The second has been fitted with a quadrilateral thigh seat, in addition to hinges and thigh lacer, in an attempt to avoid repeated breakdown of the skin of the inadequate stump. We advise against early diaphyseal amputation in this condition.
Case Report 2
D. S. was admitted at 8 months of age with Type II fihular hemimelia of the left leg. The initial findings were virtually the same as those in Case 1 ( Figure 4 ). An overall shortening of 6 cm was accompanied by marked anterior angulation. The foot was in extreme equinus and valgus position with absence of the lateral two rays. At the age of 3 months, at another institution, an osteotomy of the tibia had been performed, together with excision of the fibular fibrous band and tendon lengthening of triceps surae and peroneals. Initial immobilization had been by intramedullary Kirschner wire and plaster hip spica for a period of 10 weeks. After removal of plaster, however, deformity recurred and progressed to an angulation of approximately 90 degrees. Radiographs showed an appearance resembling delayed union at the osteotomy site ( Figure 5 ).
After consultation at this institution, treatment by conversion and prosthetic fitting was elected. A Syme ankle disarticulation was performed. Through a separate incision a trapezoid resection of midtibia with correction of angulation was carried out. A 1.5-mm Steinman pin was employed to transfix and stabilize the heel pad, and also to serve as intramedullary fixation for the osteotomy ( Figure 6 ).
Healing was prompt and uneventful. The patient was fitted at 13 months of age with an endbearing PTB hard socket with hinges, thigh corset, and toddler harness ( Figure 7 and Figure 8 ). Walking was learned quickly, and the patient has continued to walk with good gait mechanics. At the age of 6 the tibial stump has remained straight, the endbearing and stability of the heel pad are unimpaired, and there has been continued hypertrophy of the cortical bone of the shaft of the tibia, as well as continued growth from the distal tibial epiphysis ( Figure 9 and Figure 10 ).
It is anticipated that the stump will be suitable for fitting with an endbearing PTB prosthesis without hinges or thigh corset when the patient has arrived at adult gait mechanics, at about the age of 6 and 1/2 or 7. The only complication present in the stump is a dense posterior scar from his first operation which has tended to draw the heel pad slightly posterior with growth but which has not interfered with its weightbearing capacity at this time.
There has been some hesitation in the past to employ corrective transverse osteotomy in the kyphotic tibia. This bowing in fibular hemimelia is not to be confused with that seen in true congenital tibial kyphosis or pseudoarthrosis, in which failure of union is common. Coventry2 and others have pointed out this important distinction and have noted the feasibility of osteotomy for the correction of angulation in fibular hemimelia. If the procedure is correctly performed, and if the deforming forces of unbalanced muscle pull are corrected, neither reangulation nor nonunion should be a problem.
Most patients with fibular hemimelia and significant and uncorrectable shortening of the limb can be effectively treated by conversion, at the Syme or Boyd level, and prosthetic fitting. It has been observed, however, that certain patients in the Type II group with severe tibial angulation mature to a less-than-optimal configuration of the amputation stump. This deficiency may eventually interfere with effective prosthetic fitting and gait mechanics1,3,6. Loss of endbearing in the angulated stump seems to result in progressive hypoplasia of both bone and soft tissues, so that, at maturity, endurance and comfort suffer. It is suggested that a direct approach to the angulation deformity by early osteotomy at the time of conversion may help to retain the endbearing capabilities of the amputation stump and provide more optimal prosthetic function.
1. Capener, N., Editorial and annotations. Amputation surgery and prostheses. J Bone and Joint Surg, 45-B:3-5, February 1963.
2. Coventry, M. B., and E. W. Johnson, Congenital absence of the fibula. J Bone and Joint Surg, 34-A:941-995, October 1952.
3. Hall, C. B., Prosthetic socket shape as related to anatomy in lower extremity amputees. Clinic Orthop, 37:32-46, November-December 1964.
4. Kruger, L. M., and R. D. Talbott, Amputation and prosthesis as definitive treatment in
congenital absence of the fibula. J Bone and Joint Surg, 43-A:625-642, July 1961.
5. Mazet, R., Symes amputation. J Bone and Joint Surg, 50-A:1549-1563, December 1968.
6. Radcliffe, C. W., The biomechanics of below knee prostheses in normal level bipedal walking. Selected articles from Artificial Limbs, 295-303, Krieger, Huntington, New York (1970).
7. Thompson, T. C., L. R. Straub, and W. D. Arnold, Congenital absence of the fibula. J Bone and Joint Surg, 39-A:1229-1237, December 1957.
8. Wood, W. L., N. Zlotsky, and G. W. Westin, Congenital absence of the fibula. J Bone and Joint Surg, 47-A:1159-1169, September 1965.