Fibular Hemimelia (FH) is a rare disorder; it may occur as an isolated anomaly or as a part of a malformation syndrome. We present a case of fibular hemimelia in a neonate with foot deformity with normal prenatal ultrasound. The purpose of the present report is to create the awareness of the condition and to review the literature.

Abstract

Introduction

(EM) LSCS was done in view of absent beat to beat variability, variable deceleration, no acceleration in the admission CTG. Intraoperatively, liquor was clear ,female baby delivered, cried immediately after birth, anterior bowing of right lower limb noted with absence of second toe. Baby was handed over to pediatrician for further evaluation.

Following investigations were done:

1) Infantogram – congenital absence of fibula , absent meta-tarsal bones and absent right head of tibia epiphysis.

2) Abdominal scan – normal study

3) Cranium scan – normal study

4) Echo – small PDA

Case

This case highlights the difficulty of antenatal diagnosis of FH, which has been recognized in literature. It is particularly difficult if it is present in one limb. Part of the difficulty may be the fact that it is so rare. In a selected “high-risk” patient population scanned trans-vaginal scan between 12 and 16 weeks, Bronshtein et al found the incidence of skeletal anomalies to be 0.57% (42 cases in 7325 scans).4 In contrast, the frequency of these anomalies in the general population is extremely low. This discrepancy may be due to the fact that their patients were high risk and because at fetuses affected by skeletal dysplasia are at an increased risk for intrauterine death.

Development of the fetal upper and lower extremities has been documented by USG. Both the upper and lower buds are seen by the end of the 8th week of gestation. Subsequently, there is rapid growth of both upper and lower extremities, and by the end of the 10th week, the entire limbs are developed. With 4-dimensional USG, these early fetal movements can be documented. The fetal long bones can be evaluated and measured by the end of the first trimester (10th–12th week)5

The precise etiology of FH is unclear.6 However, several theories have been suggested, such as defects in the apical ectoderm ridge, defects secondary to an absent anterior tibial artery and defects in muscle development. Another proposed theory is that of a disruption of the lower limb developmental field during embryogenesis. The developmental field of the lower extremity includes the pubic portion of the pelvis, proximal femur, patella, anterior cruciate ligament, and lateral or axial foot rays. This developmental field encompasses the commonly associated defects seen with FH, namely of the femur and lateral aspect of the foot.

Classification

Achterman and Kalamachi classification, derived from clinical as well as radiographic information.

Type I, there is minimal hypoplasia of the fibula,

Type II-there is complete absence of fibula.

The therapies for FH are surgical and include limb-lengthening procedures and amputation. The decision to proceed with one or the other is usually individualized from case to case, but in cases in which there is a nonfunctional foot or a limb length discrepancy of greater than 30%, surgical amputation with early use of a prosthesis is generally recommended.

Discussion Conclusion

An obvious fetal malformation may not be apparent until all the long bones are carefully measured and evaluated. This can further be challenging when only 1 limb or part of a limb is affected.

The AIUM(American Institute of Ultrasound in Medicine) Practice Guideline for the Performance of an Antepartum Obstetric Ultrasound Examination recommends documenting the presence or the absence of the fetal extremities during the second trimester of pregnancy.

Therefore detailed fetal anatomical survey is recommended at time of routine scan, which can be difficult in Indian scenario. Explanation of the condition to the parents poses further challenges.

References1. Florio I, Wisser J, Huch R, Huch A. Prenatal ultrasound diagnosis of a

femur-fibula-ulna complex during the first half of pregnancy. Fetal Diagn Ther 1999; 14:310–312.

2. Coventry MB, Johnson EW JR. Congenital absence of the fibula. J Bone Joint Surg Am 1952; 34:941–955.

3. Lewin SO, Opitz JM. Fibular a/hypoplasia: review and documentation of the fibular developmental field. Am J Med Genet Suppl 1986; 2:215–238

4. Bronshtein M, Keret D, Deutsch M, Liberson A, Bar Chava I. Transvaginal sonographic detection of skeletal anomalies in the first and early second trimesters. Prenat Diagn 1993; 13:597–601.

5. Monteagudo A, Dong R, Timor-Tritsch IE.Fetal fibular hemimelia: case report and review of the literature Ultrasound Med. 2006;25:533-7.

6. Fordham LA, Applegate KE, Wilkes DC, Chung CJ. Fibular hemimelia: more than just an absent bone. Semin Musculoskelet Radiol 1999; 3:227–238.

The incidence of fibular has been estimated to be 5.7 to 20 cases per million births.1 In most cases, it represents an isolated and sporadic event. However, FH may be a part of a malformation syndrome. Even , though this a rare condition , it is the most common malformation among the long bone deficiency disorders.2

Shortening of the extremity is obvious at birth with leg-length discrepancy. On plain radiograph of the leg and foot, significant fibular deficiency (hypoplasia) or absence of the fibula can be seen.

Fibular hemimelia is actually a clinical spectrum ranging from mild fibular hypoplasia to fibular aplasia. The complete form is more common than the incomplete form; unilateral involvement is more common than bilateral; and the right side is more commonly affected than the left.3

Bilateral FH is seen in approximately one third of cases. In these cases, the tibiae are often straight. When FH is unilateral, the right side is more commonly affected, and anterior tibial bowing is usually present. In almost all cases, there is deficiency of the lateral foot rays. Less commonly, there is fibular aplasia with a normal number of toes, but almost never associated with polydactyly. It is twice as common in male fetuses as in female fetuses.

Fig. 2: Limb length discrepancy

A 23 years old, primigravida with non consanguineous marriage, with uneventful antenatal period. Scan done in first and second trimester was unremarkable. She presented at 40+5 weeks of gestation in latent labor.

Department of Obstetrics & Gynaecology, St.Martha’s hospital, Bangalore

Garima Nag, Diana Bernard, Padmini Issac

Fibular Hemimelia - A Case Report

Fig. 1: Right leg bowing and shortening with absent 2nd toe.

Fig. 3: Right fibular absence in the lower extremity radiograph

Fig. 4: Infantogram

Treatment options of limb lengthening procedure/ amputation was explained to the parents.

Contd….