Flared Iliac Wings

► [Widening of the iliac wings, with external rotation]

The overall iliac configuration varies considerably according as whether flaring of the iliac wings is associated with constriction of the iliac supra-acetabu-lar regions or with decreased vertical diameter of the iliac bones and unchanged basilar portions. The first iliac configuration is characteristic of the 'dysostosis multiplex,' but also occurs to a variable extent in atelosteogenesis, boomerang dysplasia, osteodys-plasty, and frontometaphyseal dysplasia. The second iliac bone configuration is seen in metatropic dyspla-sia, dyssegmental dysplasia, spondyloepiphyseal dysplasia congenita,spondylometaphyseal dysplasia Kozlowski type, and several other constitutional bone disorders.

Frontometaphyseal Dysplasia

Fig. 4.8. Mucolipidosis III in a 26-year-old man. Note flaring of the iliac wings and narrowing of the supra-acetabular iliac regions. The acetabular fossae are shallow and irregular. Irregular outline of the right femoral head, with cystic lucencies, suggests avascular necrosis. There is bilateral coxa valga. (From Wihlborg et al. 2001)

Fig. 4.8. Mucolipidosis III in a 26-year-old man. Note flaring of the iliac wings and narrowing of the supra-acetabular iliac regions. The acetabular fossae are shallow and irregular. Irregular outline of the right femoral head, with cystic lucencies, suggests avascular necrosis. There is bilateral coxa valga. (From Wihlborg et al. 2001)

Fig. 4.9. Atelosteogenesis/boomerang dysplasia in an 18-week fetus with a clinical phenotype overlapping atelosteogenesis I and boomerang dysplasia. Note marked flaring of iliac wing, and hypoplasia of the basilar portion of the ilium. (From Sil-lence et al. 1997)

In addition to flaring of the iliac wings and constriction of the iliac bodies, mucolipidosis II (I-cell disease, OMIM 252500) and III (pseudo-Hurler poly-dystrophy, OMIM 252600) feature shallow and deformed acetabular fossae, tapering of the ischial bones, small and irregular femoral heads, and coxa valga (Melhem et al. 1973) (Fig. 4.8). In mucopolysaccharidosis IV (Morquio, OMIM 252300), increased obliquity of the acetabular roofs (increased acetabu-lar angle) and marked flaring of the iliac wings are observed. The pelvic inlet shows a wine-glass-like configuration. Coxa valga and progressive dysplasia of the capital femoral epiphyses are also found (Langer and Carey 1966). In mucopolysaccharidosis III (Sanfilippo, OMIM 252900) flaring of the iliac wings is mild, the superior acetabular portion is underdeveloped, and the femoral necks are widened (Langer 1964). Flared ilia with hypoplasia of their inferior portion occur in atelosteogenesis I (OMIM 108720) and II (de la Chapelle dysplasia, OMIM 256050), and boomerang dysplasia (OMIM 112310) (Fig. 4.9). In atelosteogenesis II a medial spur of the acetabular border similar to that of chondroectoder-mal dysplasia, asphyxiating thoracic dysplasia, and short-rib polydactyly syndrome, may be found (Sil-lence et al. 1997). A phenotype similar to, but less severe than, that of dysostosis multiplex may be observed in Melnick-Needles syndrome (osteodysplasty, OMIM 309350): the iliac wings are thin and flared, with constriction at the basis of the ilium, and a sharply concave sacrosciatic notch. In addition, pubic and ischial bones are narrow (Dereymaeker et al. 1986). In frontometaphyseal dysplasia (OMIM 305620) flaring of the iliac wings is striking (Holt et al. 1972). In Down syndrome, the iliac dysplasia consists in flared iliac wings and flattened acetabular roofs that persist into adulthood (Roberts et al. 1980) (Fig. 4.10).

Metatropic dysplasia (OMIM 156530), a disorder inherited as an autosomal recessive trait, is characterized in infancy by short iliac wings with curved lateral margins and small sciatic notches. Later in life, the iliac wings become severely flared, giving rise to a 'battle-axe' appearance: the anterior superior iliac spines sometimes approach the highest portion of the horizontal acetabulum, while the iliac bodies remain hypoplastic. Broad femoral necks and deformed capital epiphyses are additional findings (Kozlowski et al. 1988) (Fig. 4.11). In addition to classic metatropic dysplasia, a clinically and genetically heterogeneous group of bone dysplasias with similar, but milder, skeletal changes has been reported under the designation 'metatropic dysplasia variants' Features common to both types include dumb-bell-shaped long bones, characteristic tongue-like projections of the lesser trochanters, platyspondyly of varying degree (from wafer-like vertebrae in the classic form to mild flattening in the variants), and short, broad, flared ilia with supra-acetabular notches (Nishimura et al. 1998) (Fig. 4.12). Spondylometaphy-seal dysplasia, Kozlowski type (OMIM 184252) dis-

Mildest Form Down Syndrome
Fig. 4.10. Down syndrome in an adult female patient. Observe marked flaring of the iliac wings, resembling Mickey Mouse ears. The acetabular roofs are flat, and the femoral necks show moderate valgus deformity
Deformed Femur
Fig. 4.11. Metatropic dysplasia in a 9-year-old girl. There is severe flaring of the iliac wings, with low-set anterosuperior iliac spines and hypoplastic basilar portions of the ilia. The capital femoral epiphyses are small and deformed, and proximal femoral metaphyses are broad and irregular
Mickey Mouse Iliac Wing
Fig. 4.12. Metatropic dysplasia variant in a girl aged 3 years and 8 months. Note marked flaring of the iliac wings, the supra-acetabular notches corresponding to the superior iliac spines, prominent lesser trochanters, short femoral necks, and platyspondyly. (From Nishimura et al. 1998)

plays short and flared ilia with small sacrosciatic notches, and irregular,horizontally oriented acetabu-la. Iliac wing flaring also occurs in the mild variety of dyssegmental dysplasia, Rolland-Desbuquois type (OMIM 224400) in association with small sacrosciatic notches and broad pubis and ischia (Aleck et al. 1987). Mild iliac flaring is observed in spondyloepiphyseal dysplasia congenita (OMIM 183900). In this condition, however, striking features include severe delay in the ossification of the pubic bones and proximal femurs, progressive coxa vara, and premature osteoarthritis (Spranger and Langer 1970).

While the radiographic stigmata of nail-patella syndrome (OMIM 161200) take the form of the characteristic iliac horns at all ages, flaring of the iliac wings occurs in late adolescence and adulthood (Williams and Hoyer 1973).

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