Fibular Hemimelia Treatment & Management

No specific medical therapies can correct the underlying abnormalities for fibular hemimelia. However, for mild deformities, observation and/or nonoperative management may be useful.

As with limb-length discrepancies resulting from other causes, no treatment may be necessary or the use of heel lifts may be adequate, particularly in discrepancies less than 2 cm. However, although the percentage of shortening generally remains constant at 10-20% relative to the contralateral side, the absolute discrepancy may progress with growth and must be followed until skeletal maturity.^[16]

Similarly, observation may be adequate for hip varus, genu valgum, tibial kyphosis, and patellar instability. Although an absent anterior cruciate ligament (ACL) with a positive Lachman test result is observed frequently, clinical signs of instability are rare, and nonoperative management is appropriate.^[17] In mild cases, ankle valgus may be managed with a University of California-Berkeley (UCB) orthosis, but as with limb-length discrepancy, the patient must be monitored throughout his or her growth because the fibular portion of the mortise may be progressively compromised.

Several issues must be addressed before any procedure is performed for postaxial hypoplasia of the lower extremity (fibular hemimelia). The ultimate goal is to achieve symmetrical, stable, and well-aligned joints with the minimal number of surgical procedures. No single set of operations should always be performed; instead, individual procedures should be planned that address the specific abnormalities in each patient. Finally, realistic expectations of the timing, the duration of recovery, and the ultimate outcome must be communicated to the patient and to his or her family.^[18]

In patients with a nonfunctional foot, Birch et al recommend amputation, regardless of limb-length discrepancy, unless the upper extremities also are nonfunctional.^[19] In patients with a functional foot, the surgical recommendations generally fall into 1 of 3 groups:

• Patients with a discrepancy less than 10%. There is little disagreement that these patients can benefit from lengthening procedures or contralateral epiphysiodesis.
• Patients with a discrepancy more than 30%. Amputation is recommended for these patients; again, there is little disagreement on management.
• Patients with a discrepancy of 10-30%. This group of patients represents the greatest challenge. Lengthening more than 10 cm in a limb with associated knee, ankle, and foot abnormalities is difficult. At maturity, an average lower-extremity length is 80-110 cm; a 10% discrepancy for such a limb is 8-11 cm. Although parents have hopes for a normal limb, they must be helped to understand the problems associated with lengthening in cases of severe deficiencies. Lengthening with a contralateral epiphysiodesis may be considered as an alternative to multiple lengthening procedures.

If amputation is determined to be the most appropriate procedure for an individual, the Syme amputation is generally used. In the past, transtibial amputation was performed more commonly because of cosmetic concerns for a bulky ankle. However, subsequent observations showed that the ankle does not enlarge with growth after the Syme amputation, and that the procedure allows weight bearing on the residual limb. Boyd described a modification to the Syme amputation in which the talus is removed, but the retained calcaneus is fused to the tibia to help prevent posterior migration of the heel pad.^{[20, 21]} In this modification, the heel pad grows with the patient. However, the procedure is associated with more wound problems, nonunion, and malpositioning of the calcaneus. Thus, the unmodified Syme amputation is generally recommended.^[22]

When a Syme amputation is performed in children, trimming the condyles is not necessary. As opposed to adults, children have small condyles that do not grow to a normal size.

For patients with hip dysplasia, PFFD, and/or coxa vara, please refer to Developmental Dysplasia of the Hip, Proximal Femoral Focal Deficiency, and Congenital Coxa Vara for further details on the various treatment procedures.

Several issues should be noted, however. Any necessary operations for acetabular redirection are generally performed before femoral lengthening. Also, in the setting of combined coxa vara and limb-length discrepancy, lengthening via callotasis at the subtrochanteric level is not recommended because of the bending moment and the small cross-sectional area in that portion of the femur. Instead, a more standard valgus intertrochanteric osteotomy should be performed with any necessary lengthening performed separately at the distal femur.

Genu valgum associated with postaxial hypoplasia of the lower extremity is progressive, and it can adversely affect alignment of the lower limb. This can be treated in several ways. Acute correction can be obtained by means of a distal femur corticotomy during a femoral lengthening procedure or by means of an osteotomy during correction of anteromedial tibial bowing. In patients with a hypoplastic lateral femoral condyle, temporary medial epiphyseal stapling has been recommended because osteotomy has a high recurrence rate unless it is performed near maturity.

Ankle abnormalities can range from complete absence of the fibula to ankle valgus and/or a ball-and-socket ankle.^[23] For the more severe deformities, a Gruca reconstruction has been described.^[24] This procedure creates a lateral malleolus by using an oblique sliding osteotomy of the distal tibia. In milder cases of fibular hypoplasia and possible valgus, a supramalleolar osteotomy is traditionally used. As a less-invasive alternative, a medial malleolar screw epiphysiodesis may provide good results, as Stevens described.^[25]

Procedures in the foot include resection of talar coalitions or fusions and addressing any problems with shoe fit that might arise for any deformity. Specific details of these procedures are discussed in other articles.

As mentioned above, the most important part of preoperative planning is thorough evaluation of the entire limb to identify all of the associated abnormalities that may be present as a part of fibular hemimelia. The mechanical and anatomic axes should be determined and corrected when possible. An overall plan is important, and should be discussed in detail with the patient and his or her family.

Postoperative care for postaxial hypoplasia of the lower extremity (fibular hemimelia) depends on the specific procedures performed.

Because the abnormalities associated with postaxial hypoplasia of the lower extremity (fibular hemimelia) tend to be relative as opposed to absolute, the patient should continue to be monitored through maturity to ensure that no additional interventions are necessary.

Postaxial hypoplasia of the lower extremity (fibular hemimelia) is a syndrome that involves structures throughout a large anatomic area, and complications of treatment are not infrequent. In addition to the standard surgical complications (eg, infection, bleeding), several complications specific to this disorder have been described.

In the hip, the Hilgenreiner epiphyseal angle must be corrected to less than 38° from the horizontal; repeat valgus intertrochanteric osteotomies may be needed.^[26] Limb lengthening has a range of complications, from the frequent superficial infections along the pin tract to more significant problems related to fracture, tightening of soft tissues, stiffness, and recurrent deformity.

Stapling is an effective method for correcting angular deformities, but staple displacement and/or rebound growth may occur. However, in some situations, stapling may be preferable to an osteotomy because of the increased morbidity rate and because of the possibility of nonunion and recurrence after an osteotomy procedure.

Finally, amputation may ultimately be necessary despite limb-sparing treatment, a possibility that must be discussed with the parents from the beginning.

Because postaxial hypoplasia of the lower extremity (fibular hemimelia) represents such a wide range of abnormalities with varying degrees of involvement, no simple statement can be made regarding the patient's prognosis. Judiciously chosen, well-timed procedures specifically tailored to the individual patient provide the best prospects for a well-aligned, functional limb of adequate length.^[27]

One controversy regarding postaxial hypoplasia of the lower extremity (fibular hemimelia) is its name. Historically, it has been called fibular aplasia or hypoplasia. This name has been defended largely because of historical precedent. However, as more insights have been gained into the constellation of related abnormalities stemming from the embryological limb bud, postaxial hypoplasia of the lower extremity may describe the syndrome more accurately. It also helps remind the clinician to look for other subtle abnormalities and not focus on only the obvious fibular deficiency.