Fibular hemimelia

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 93323

Definition

Fibular hemimelia is a congenital longitudinal limb deficiency characterized by complete or partial absence of the fibula bone.

Epidemiology

Prevalence is estimated at 1 in 50,000. A slight male preponderance has been reported in some studies, whereas other reports describe an equal sex distribution.

Clinical description

Unilateral involvement occurs in two-thirds of cases, with the right fibula being affected more often than the left. Agenesis of both fibulae is rare. Fibular hemimelia may vary from partial absence of the fibula (10% of cases) with relatively normal-appearing limbs, to absence of the fibula with marked shortening of the femur, curved tibia, bowing of the leg, knee joint and ankle instability and significant soft tissue deficiency. The major functional deficiency results from leg length discrepancy in unilateral cases or asymmetrical dwarfism in bilateral cases. The foot is generally in an equinovalgus position. As there is limited growing potential within the affected bone, the extent of the deformity tends to increase with growth. Occasionally, fibular hemimelia is associated with congenital shortening of the femur (femur-fibula-ulna complex; see this term). Other skeletal anomalies (craniosynostosis, syndactyly, brachydactyly, oligodactyly and ectrodactyly) may also be present. Fibular hemimelia is also found in several generalized skeletal dysplasias and dysostoses. Rarely, fibular hemimelia is associated with nonskeletal malformations (eye abnormalities such as anterior chamber anomalies or anophthalmia, cardiac anomalies, renal dysplasia, thrombocytopenia, thoracoabdominal schisis, spina bifida and, rarely, intellectual deficit). Fibular hemimelia can be present in some chromosome anomalies.

Etiology

The etiology is unclear. The deformity is probably due to disruptions during the critical period of embryonic limb development, between 4th and 7th week of gestation. Vascular dysgenesis, viral infections, trauma and environmental influences have been suggested as possible causes.

Diagnostic methods

Diagnosis is based on clinical examination and X-rays.

Differential diagnosis

Differential diagnoses include amniotic band syndrome, thalidomide embryopathy and several skeletal dysplasias and dysostoses with asymmetrical involvement of the lower limbs such as femoral-facial syndrome (see these terms).

Antenatal diagnosis

Prenatal diagnosis of fibular hemimelia has been reported.

Genetic counseling

Most cases are sporadic. A family history has been reported in a small percentage of cases with an autosomal dominant pattern of inheritance and incomplete penetrance.

Management and treatment

Management requires a multidisciplinary approach (genetic counselors, perinatologists and pediatric orthopedic surgeons). Orthopedic treatment aims at correcting the leg length discrepancy, and, in bilateral cases, correcting the asymmetrical dwarfism. In less severe cases with minimal hypoplasia of the fibula and only mild limb length discrepancy, special shoes and/or accommodative insoles may be used to equalize limb length. In some mild cases, epiphysiodesis on the contralateral (normal) side is also an option. In moderate limb length inequality, limb lengthening is an option but it carries the risk of requiring multiple reconstructive procedures and complications. Rarely, for cases of severe limb length discrepancy or complete absence of the fibula when the foot is nonfunctional, amputation with prosthetic fitting in early childhood may be considered.

Prognosis

Fibular deficiency is usually a benign condition, although in severe cases it can be debilitating. Acceptable functional results may be achieved by surgery. In case of syndromic presentation, prognosis depends on the nature of the associated anomalies.

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