Department of Gynecology, Félix Guyon Hospital, 97400 Saint-Denis, Réunion Island, France.
Department of Genetic, Félix Guyon Hospital, 97400 Saint-Denis, Réunion Island, France.
Echographic consulting room, Moufia Street, 97400 Saint-Denis, Réunion, France.
Tel : 0262 90 55 40. Fax : 0262 90 77 30.

Introduction
With the use of high resolution ultrasound, there has been an increased awareness of exceptional, but detectable skeletal malformation syndromes. Nevertheless a correct diagnosis is essential for genetic counseling, for pediatric orthopedic counseling and management of the pregnancy [1-2]. Recently, congenital absence of fibula condition was detected by high resolution ultrasound at 24 weeks in a fetus without family history.

Case report:
A 25-year-old patient, gravida 1, para 0, with no notable medical history, was referred to our department at 25 weeks of gestation for a fetal unilateral lower limb malformation. The pregnancy was otherwise uncomplicated and the mother neither took medication nor had prior infectious diseases. Ultrasound examination at her first visit at 12 weeks, revealed a single viable fetus with a normal amount of amniotic fluid and nuchal translucency. Ultrasound examination at 24 weeks revealed a single viable fetus with measurements consistent with gestational age. Amniotic fluid was normal. Abnormalities, all located on the right lower limb, included unilateral agenesis of the fibula, hypoplastic tibia and unilateral club-foot with three metatarsal bones (Image 1-3).

The thumbs appeared to be normal as the reminder of the anatomic survey was normal. After the parents were informed by a pediatric orthopedic surgeon about the risks and the future handicaps for the neonate, they decided to continue the pregnancy. The fetal karyotype was normal. The baby was born at 38 weeks. Neonatal examination revealed a short right lower extremity (Image 4).

The left foot, the arms and the fingers were normal. Neonatal X-rays of the skeletons radiographs confirmed unilateral absence of the fibula (Image 5). The right feet was clubbed and there was two toes and two metatarsal bones. The therapeutic project is the amputation of the right leg.

Discussion:
Fibular hemimelia is a congenital deficiency or absence of the fibula. There is a spectrum of disease from mild fibular hypoplasia to fibular aplasia. The ipsilateral tibia may be hypoplastic, bowed or normal [3-4]. Fibular hemimelia can be frequently associated with proximal focal femoral deficiency, deficiencies of the lateral aspect of the foot, or is part of a malformation syndrome [4]. The syndrome caused by congenital absence of the fibula has another number of frequently associated pathologic abnormalities, which are illustrated by the case reported.

The syndrome "congenital absence of fibula" is also called:

• Femur-fibula-ulna syndrome
• Intercalary hemimelia of the fibula
• Fibula, congenital deficiency of proximal femoral focal deficiency
• Congenital short tibia with absent or dysplastic fibula [5].

Usually sporadic (the recurrence risk for the patient's siblings is negligible), although a familial incidence (autosomal recessive) has been reported in a small percentage of cases [6-7]. Embryologic studies indicate a development insult to the embryo at about the fifth or sixth week of intrauterine life. Fibula abnormalities vary from a partial absence, with relatively normal-appearing limbs, to absent fibula, with marked shortening of the femur, curved tibia and serious foot anomalies.

Generally three types of congenital absence of fibula have been recognized.

1. TYPE I: Includes cases with unilateral or partial absence of the fibula, with mild or no bowing of the tibia (10 % of the cases). The leg may or may not be shortened.
2. TYPE II: Patients have unilateral absence of the fibula, anterior bowing of the tibia with dimpling foot deformity with absent rays, and marked shortening of the leg. This form is observed in about 35 % of the cases.
3. TYPE III: The remaining 55 % of the patients have unilateral or bilateral absence of the fibula, with the same leg and foot deformities above described and multiple other skeletal defects.

Diagnosis:
The diagnosis of congenital absence of fibula is made by the absence of the fibula with commonly associated clubfoot. When associated, tibial bowing and foot deformities are probably the result of abnormal attachments of the fibular muscles, resulting in abnormal stresses on the developing tibia and the foot, respectively. Other findings can also be diagnosed [9-10].

The most common associated anomaly is proximal femoral deficiency syndrome [11]. Other anomalies include:

• cardiac anomalies,
• thrombocytopenia absent-radius (TAR) syndrome
• thoraco-abdominal schisis
• spina bifida and
• renal anomalies [12-13]

But most associated anomalies are skeletal and include:

• Peromelia (severe anomalies of distal limbs including absence of hand or foot)
• congenital dislocation of the head of the radius [13]
• craniosynostosis
• syndactyly
• brachydactyly and
• clinodactyly of fingers and toes and facial dysmorphism.

Fibular agenesis/hypoplasia is the most common reduction malformation affecting the long bones. Nevertheless agenesis of both the fibulae, is rare. The degree of fibular deficiency ranges from unilaterally short to bilaterally absent. A case of occurrence in four consecutive pregnancies has been reported once [14].

Differential diagnoses include amniotic band syndrome, campomelic dysplasia, mesomelic dysplasia and other skeletal dysplasias with asymmetrical involvement of the lower limbs such as femoral-facies syndrome (FFS). and fetal thalidomide syndrome [15].  Femur-fibula-ulna complex (FFU) is not considered because generally there is asymmetric femoral hypoplasia and hypoplasia of both tibiae and malformation of the hand [16].

In sporadic non-lethal skeletal dysostosis, the spectrum of malformations is highly variable, with no disorder being common to all patients.

Tibial hemimelia syndrome (THS) encompasses several syndromes, all involving tibial agenesis or hypoplasia and polydactyly [17]. Variable expressions of these clinical findings have been described. THS is associated with bilateral tibial agenesis, clubbing and polysyndactyly of the feet and five triphalangeal finger hands. Unlike bilateral hemimelia syndrome, a rare autosomal dominant condition, unilateral tibial hypoplasia is rarely described. The present case emphasizes the importance of establishing a correct antenatal diagnosis in order to counsel patients for subsequent pregnancies and treatment.

Prognosis is good with regard to mental development and life span. Standard obstetrical management is not altered. Outcomes are mainly dependent on the severity of the limb malformation and the need for orthopedic surgery [16]. Rehabilitation varies depending on the severity of the limb deficiency. Fibular deficiency is usually benign, and leg length inequality may be corrected by epiphysiodesis, leg lengthening, ankle reconstruction using the Gruca technique [18] or simply a shoe raise. Postsurgical therapy on the involved extremity should take into account the patient's lack of joint motion within the tarsal region. With this in mind, special shoes or accommodative insoles, alone or in combination, should be prescribed in order to facilitate an increase in weightbearing activity with minimal discomfort. Rarely when the foot is nonfunctional, amputation may be considered [19].

The treatment varies drastically with simply equalizing leg length in Type I deficiency, and possible amputation of the foot and fitting of a prosthesis in Type II deficiency to obtain satisfactory function [20]. In France, termination of pregnancy for medical reasons are accepted if gestation is potentially dangerous for the mother or when fetal malformations are lethal and or incurable. In our case, the pediatric orthopedic surgeons confirmed that the limb defect could not totally cured, leaving the child with a permanent limp even after several operations. The parents were offered an opportunity to meet a young boy treated for the same conditions and they opted for continuation of pregnancy.

CONCLUSION :
The syndrome caused by congenital absence of the fibula has a number of pathologic abnormalities frequently associated with it, which are illustrated by the case reported. The parents must be advised that leg amputation is possible though intellectual capacity is normal.

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