PubMed · 12960638
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David R Hootnick. Fibular hemimelia: a new classification system.. https://doi.org/10.1097/01241398-200309000-00022
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The development of the iliac bones and lower limbs are parallel processes depending on the normal ontogeny of the caudal blastema [O'Rahilly and Müller, 1989; Opitz, 1993; Opitz et al., 2000]. We hypothesized that the pathogenetic mechanisms leading to fused lower limbs would in parallel displace the ilia caudally and medially and that the degree of this displacement might correlate with the severity of the iliac and lower limb defects. Thus the purpose of the study was to test this hypothesis in a sample of 12 sirenomelic fetuses. The fetuses GA 16-39 weeks, spontaneously or therapeutically aborted, were radiographed in the frontal projection as part of a requested autopsy. From each radiograph, a line was drawn connecting the most cranial part or the two ilia. After that the distance was measured vertically between this line and the most cranial part of the first sacral vertebral body (iliac-sacral distance (ISD)). A second distance was measured horizontally between the most lateral part of the two iliae (bi-iliac distance (BD)). As a result, ISD correlates with the iliac/femur phenotype. Separate ilia and femora occur only in cases with normal ISD. Fused ilia or femora or both are seen only in fetuses with mildly increased ISD, whereas a single iliac bone and femur occur only in cases with greatly increased ISD. The increase of the ISD does not correlate with the severity of more distal limb involvement. There was a correlation between the ISD and the BD values; the higher the ISD, the shorter the BD. Based on these findings, we propose an extended classification of Sirenomelia to be tested by other researchers.
Sirenomelia is a rare congenital anomaly with incidence of 1.5-4.2 per 100,000 births. Vascular steal phenomenon, posterior axial mesodermal defect or teratogenic defects have been implied in its pathogenesis. The authors present two cases with associated upper limb involvement and vertebral defects and complete absence of one lower limb bones in one case. Autopsy revealed abnormalities in internal organs. Both cases were associated with single umbilical artery and severe oligohyramnios. Sirenomelia should be suspected in antenatal period in cases presenting with severe oligohydramnios and intrauterine growth retardation for a early diagnosis and appropriate management of pregnancy.
Fibular hemimelia is associated with a deformity of the distal tibial epiphysis resulting in a convexity with lateral and posterior slope of the distal joint surface. The deformity results into an equinovalgus position of the foot and ankle and frequently consecutive dislocation of the foot. A new procedure is presented, in with a metaphyseal ostotomy is performed towards the physis in order to bend the postero-lateral third of the distal tibial epiphysis forming a concave distal tibial joint surface. This procedure was done in four feet in three patients at ages between 7 and 20 months combined with soft tissue releases and rebalancing the tendons. At a follow-up between 6 and 42 months the position of the feet is well retained.