Small Hypoplastic Pelvis

► [Underdeveloped pelvis]

Pelvic hypoplasia itself is a nonspecific feature of several constitutional bone diseases. As such, it is of limited diagnostic value when considered alone. Nevertheless, pelvic hypoplasia is seldom 'harmonic,' as it is most commonly associated with changes in the pelvic shape that may provide important clues to the radiographic recognition of specific disorders. This section summarizes some of these configurations associated with pelvic hypoplasia. The disorders in which individual portions of the pelvis are hypoplas-tic are also mentioned. The topic of hypoplastic pubic rami is addressed in a separate section in this chapter.

In children with thanatophoric dysplasia (OMIM 187600) the pelvis is markedly hypoplastic, with squared iliac bones, small sacroiliac notches, horizontal acetabular roofs with peripheral spikes, and short and wide pubic and ischial rami. Additional radiographic manifestations in this early lethal bone dysplasia include marked rhizomelic limb shortening, bowing of long bones (the femurs resemble telephone receivers), very short ribs, and severe platy-spondyly (Fryns et al. 1978). The overall radiographic appearance of the pelvis may be indistinguishable from, but is usually more severe than, that of homozygous achondroplasia (Pauli et al. 1983; Stanescu et al. 1990). Similar but much milder findings occur in heterozygous achondroplasia (OMIM 100800). In this condition the ilia are longitudinally shortened owing to overgrowth of the body and relative undergrowth of the iliac wing with lack of normal flaring, a pattern resulting in squared-off iliac bones (Silverman 1993). Small sacrosciatic notches, narrow sacrum, and horizontal acetabuli are additional features (Langer et al. 1967). In hypochondroplasia (OMIM 146000) clinical and radiographic signs are often subtle, leading to underdiagnosis. Shortening of the iliac bones, with small sciatic notches and flattened acetabuli, can be seen. The correct diagnosis is based on recognition of the following triad: normal facies, short stature, and lack of the normal craniocaudal increase in the interpediculate distance in the lumbar spine (Appan et al. 1990). Infants with asphyxiating thoracic dysplasia (Jeune syndrome, OMIM 208500) show squared-off iliac bones with round lateral borders and short pubic and ischial bones. The acetabular roofs are horizontal, with downward spike-like projections at the medial, lateral and - in some cases - central portions, giving them a 'trident' appearance. Sciatic

Fig. 4.1. Chondroectodermal dysplasia in a 25-week male fetus. Note vertically shortened ilia, and small sciatic notches with hook-like downward projection of the medial aspects of the acetabula. This appearance of the pelvis is indistinguishable from that of asphyxiating thoracic dysplasia and short-rib/polydactyly syndrome. (From Sergi et al. 2001)

notches are small, and premature ossification of the femoral capital epiphyses occurs. These features tend to come closer to normal with increasing age (Oberklaid et al. 1977). In infants with chondroectodermal dysplasia (Ellis-van Creveld syndrome, OMIM 225500) the pelvis is similar in all respects to that seen in asphyxiating thoracic dysplasia and short-rib/polydactyly syndrome (Kozlowski et al. 1972) (Fig. 4.1). Hand polydactyly, a constant feature in Ellis-van Creveld syndrome and an inconstant one in asphyxiating thoracic dysplasia, may sometimes allow radiographic differentiation. In achondrogene-sis, a condition characterized by severely deficient ossification of the skeleton, the pelvis has small and deformed iliac bones, with poorly ossified or un-ossified sacrum, ischial and pubic bones. Features in achondrogenesis type IA and IB (OMIM 200600, 600972) are usually more severe than those of type II (Langer-Saldino, OMIM 200610). When it is not possible to decide with certainty which of the two types is present, the identification of crescent-shaped medi-

Fig. 4.2. Schneckenbecken dysplasia in a 22-week male fetus. Observe typical snail-like appearance of the right ilium, showing a peculiar projection of its medial portion. Same case as in Fig. 2.41. (From Nikkels et al. 2001)

al and inferior iliac borders makes the diagnosis of Langer-Saldino rest likely (van der Harten et al. 1988). Whether hypochondrogenesis and achondrogenesis type II (Langer-Saldino) are part of the spectrum of severity of the same disorder (Borochowitz et al. 1986a) or represent allelic variants (Hendrickx et al. 1983) is uncertain. Mutations in the COL2A1 gene, resulting in reduction of type II collagen in the cartilage, have been identified in both disorders (Horton et al. 1987). The phenotype is much milder in hypochondrogenesis than in achondrogenesis type II. The autosomal dominant spondyloepiphyseal dysplasia congenita (OMIM 183900), another condition with abnormal type II collagen (Murray and Rimoin 1988; Anderson et al. 1990), represents the nonlethal counterpart of hypochondrogenesis/achon-drogenesis type II. Distinct features in the pelvis include delayed ossification of the pubic bones and proximal femurs, and hypoplastic ilia. Premature osteoarthritis of the hips may be the sole manifestation in mild cases (Kozlowski et al. 1977b). Fibrochondro-genesis (OMIM 228520), a rare lethal chondrodyspla-sia, is characterized by very short long bones with flared metaphyses, platyspondyly, thin and short ribs with cupped ends, and small pelvis, with rounded lateral borders and small sacrosciatic notches (Whitley et al. 1984). Severe hypoplasia and a very peculiar configuration of the pelvis is seen in schneckenbecken dysplasia (OMIM 269250) (from German, snail pelvis). This rare and early lethal condition of autosomal recessive inheritance is characterized by small ilia, flat and horizontal acetabula, narrow chest with short ribs, platyspondyly, large skull, short and wide fibulas, and very short tubular bones looking like dumb-bells because of their ends (Borochowitz et al. 1986b). The appearance of the iliac wings, shaped in the form of a snail, is unique to this condition

(Knowles et al. 1986; Camera et al. 1991) (Fig. 4.2). Dyssegmental dysplasia, Silverman-Handmaker type (OMIM 224410) involves a characteristic appearance of the pelvis: the iliac bones are short, round and densely calcified (Handmaker et al. 1977). Flared ilia are typically found in the milder Rolland-Des-buquois type (OMIM 224400). Small sacrosciatic notches, and broad pubis and ischia are common to both types. In patients with metatropic dysplasia (OMIM 250600) the body proportions characteristically change with age. Neonates and infants are of normal overall body length, with a disproportionately long trunk and short extremities. In childhood and adulthood, a type of short-trunk dwarfism with progressive kyphoscoliosis becomes apparent. Radiographic features in infancy include severe shortening of the tubular bones, with metaphyseal widening of an extreme degree (dumb-bell appearance); elongated, narrow thorax; poorly ossified, broad, or diamond-shaped vertebral bodies; and hypoplastic pelvis, with round, crescent-shaped iliac wings, flat acetabula, and small sacrosciatic notches. In later life the tubular bones remain short, with trumpet-like metaphyses and epiphyseal dysplasia; the vertebral bodies become flat and anteriorly wedged, giving rise to progressive kyphoscoliosis; the iliac crests become markedly flared; and the capital epiphyses are very small, in contrast to the other parts of the proximal femurs, which are large and deformed (Kozlowski et al. 1977a). In metaphyseal dysplasia, McKusick type (OMIM 250250), the pelvis is uniformly hypoplastic, with shallow acetabular fossae and small inferior iliac spine (McKusick et al. 1965). Patients with Stickler syndrome (arthro-ophthalmopathy,OMIM 108300), a connective tissue disorder of autosomal dominant inheritance, show a marfanoid habitus, severe progressive myopia, cleft palate, micrognathia, and enlarged joints (knee, wrist and ankle) at birth. Radio-logically, features include narrow diaphyses of the long bones, with thin cortices, irregular and hypo-plastic epiphyses, wide femoral neck with coxa valga, hypoplastic iliac wing, narrow sciatic notches, and flat acetabula (Opitz et al. 1972). 'Thoracopelvic dysostosis' (OMIM 187770) means the association of narrow chest and small pelvis, with a very distinctive, heart-shaped pelvic inlet (Bankier and Danks 1983). Thoracopelvic dysostosis shares phenotypic and radiographic similarities with thoraco-laryngo-pelvic dysplasia (Barnes syndrome, OMIM 187760) and may represent a contiguous gene syndrome (Marik et al. 2000). Laryngeal involvement in Barnes syndrome is the distinguishing feature. An association of pelvic dysplasia and arthrogrypotic changes in the lower

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Fig. 4.3 a, b. Pelvis-shoulder dysplasia in a male patient at a 7 years and b 25 years of age. Note severely hypoplastic ilia, small and dysplastic acetabula with bilateral hip dislocation, and broad, curved ischial bones. Prominent iliac crest ossification centers, not fused with the iliac bones, are apparent in b. (From Hauser et al. 1998)

Fig. 4.3 a, b. Pelvis-shoulder dysplasia in a male patient at a 7 years and b 25 years of age. Note severely hypoplastic ilia, small and dysplastic acetabula with bilateral hip dislocation, and broad, curved ischial bones. Prominent iliac crest ossification centers, not fused with the iliac bones, are apparent in b. (From Hauser et al. 1998)

Coxa Valga

Fig. 4.4. Hypoplastic pelvis-facial dysmorphism-spondylope-ripheral dysplasia. Note small iliac bones, shallow acetabula, and bilateral coxa valga. The capital femoral epiphyses are also hypoplastic. Note relative shortening of the bones in the shanks relative to the femurs. (From Kitoh and Lachman 2001)

Fig. 4.4. Hypoplastic pelvis-facial dysmorphism-spondylope-ripheral dysplasia. Note small iliac bones, shallow acetabula, and bilateral coxa valga. The capital femoral epiphyses are also hypoplastic. Note relative shortening of the bones in the shanks relative to the femurs. (From Kitoh and Lachman 2001)

limbs, or pelvic hypoplasia/lower limb arthrogryposis (OMIM 602484), has been reported in sibs (Ray et al. 1986; Sarralde et al. 1998). The pelvis shows marked hypoplasia of the iliac bones, irregular acetabula, widened triradiate cartilages, and delayed ossification of the femoral heads. Fuhrmann syndrome (OMIM 228930) is an association of fibular hypopla-sia/aplasia,severe femoral bowing, and digital anomalies (polydactyly, syndactyly, oligodactyly) (Fuhrmann et al. 1980). Pelvic hypoplasia and congenital hip dislocation are additional features. Fuhrmann syndrome is a separate entity distinct from Fuhrmann dysplasia (OMIM 126950), in which tall vertebrae are the diagnostic clue. Limb/pelvis-hypo-plasia/aplasia syndrome (Al-Awadi/Raas-Rothschild syndrome, OMIM 276820), a condition with severe deficiency of the four extremities, also shows pelvic and sacral hypoplasia, deformity of the thoracic cage, and unusual facies (Al-Awadi et al. 1985; Raas-Rothschild et al. 1988; Camera et al. 1993). Another malformation pattern, referred to as aplasia/hypoplasia of pelvis, femur, fibula, and ulna with abnormal digits and nails (OMIM 601849), overlapping with Fuhrmann and Al-Awadi/Raas-Rothschild syndromes, has been reported in four children of an inbred Muslim family from Pakistan. Skeletal abnormalities include hypoplasia of the pelvis, aplasia/hypoplasia of the ulnas and femurs, fibular aplasia, digital abnormalities, and absent/dysplastic nails (Kumar et al. 1997). This condition also shows similarities to the femur-fibula-ulna syndrome (FFU syndrome, OMIM 228200).

Severe hypoplasia of ilia, scapulae, and clavicles are features of the pelvis-shoulder dysplasia (sca-puloiliac dysostosis, OMIM 169550), manifesting with rib anomalies, spina bifida, and inconstant eye anomalies (Kosenow et al. 1970; Elliott et al. 2000)

Inbred Facial Features
Fig. 4.5. Ischiospinal dysostosis in a 10-year-old girl. Note the total absence of ossification of the ischial rami and lumbosacral hypoplasia. (From Nishimura et al. 1999)

(Fig. 4.3A,B). Hypoplastic pelvis, facial dysmorphism, and mental retardation have been described in a 9-year-old Japanese boy in association with a generalized skeletal dysplasia resembling spondyloperi-pheral dysplasia (OMIM 271700), a rare disorder presenting with short stature, platyspondyly, and brachydactyly (Fig. 4.4). Distinctive features in this case included small flared ilia, shallow acetabula, and coxa valga; cutaneous syndactyly in the hands and feet; and lack of short stature (Kitoh and Lachman 2001).

Hypoplasia of the ischial bones is an extremely rare congenital malformation, which can occur as an isolated anomaly or as a syndromic constituent in such disorders as ischiopatellar hypoplasia, ischio-vertebral dysplasia, acrofacial dysostosis syndrome of Rodriguez, and ischiadic hypoplasia with renal dysfunction, immunodeficiency, and polydactyly. Ischial hypoplasia has been reported in association with segmental anomalies of the spine (butterfly vertebrae, fused vertebrae, hemivertebrae, lumbosacral agenesis). This malformation complex has been designated ischio-spinal dysostosis (Nishimura et al.

Ischial Rami
Fig. 4.6 a, b. Ischiovertebral dysplasia: pelvic radiographs in (a) a daughter and (b) her grandmother. Observe defective ossification of the ischial rami and flattened femoral heads. (From Cohen et al. 1999,)

1999) (Fig. 4.5). It is not clear whether this last disorder represents a distinct entity or is part of the malformation spectrum of ischiovertebral dysplasia. Ischiopatellar dysplasia (small patella syndrome, OMIM 147891), a disorder inherited as an autosomal dominant trait, is characterized by patellar hypopla-sia, ischial hypoplasia, and a variety of lower limb malformations, including ball-and-socket ankle joints, pes planus, tarsal coalition, calcaneal exos-toses, and shortening of the 4th and 5th metatarsals (Scott and Taor 1979; Azouz and Kozlowski 1997). Ischiovertebral dysplasia is a probably autosomal dominant disorder featuring incomplete development of the ischial rami, a peculiar facies with retro-gnathia and high-arched palate, and severely progressive kyphoscoliosis (Dubousset et al. 1994; Cohen et al. 1999). The ischial rami can be hypoplastic or aplastic (Fig. 4.6 a,b). Only occasionally have multiple segmental anomalies of the spine been described in ischiovertebral dysplasia. Although this disorder resembles cleidocranial dysplasia, the absence of clavicular and skull defects clearly identifies patients with ischiovertebral dysplasia.

Tibial Spine Abnormality

Fig. 4.7. Ischial hypoplasia-tibial hypoplasia-facial abnormalities in a 3-year-old girl. Note broad, hypoplastic ischial rami, with wide ischiopubic synchondroses. There is hypoplasia of the lesser trochanters, bowing of the tibias and fibulas, tibiofibular diastasis, and abnormal tibiotarsal joints. (From Nishimura et al. 1998,)

Fig. 4.7. Ischial hypoplasia-tibial hypoplasia-facial abnormalities in a 3-year-old girl. Note broad, hypoplastic ischial rami, with wide ischiopubic synchondroses. There is hypoplasia of the lesser trochanters, bowing of the tibias and fibulas, tibiofibular diastasis, and abnormal tibiotarsal joints. (From Nishimura et al. 1998,)

Moreover, the ossification delay involves the ischial rami in ischiovertebral dysplasia and the pubic rami in cleidocranial dysplasia; iliac wings are not affected in ischiovertebral dysplasia, while they are narrow in cleidocranial dysplasia; finally, the capital femoral epiphyses are flattened in ischiovertebral dysplasia and are enlarged in cleidocranial dysplasia. The spinal curvature is structural, and possibly secondary to hypoplasia of the anterior portion of the vertebral bodies. Spinal cord or nerve root compression is a common complication. Other features include partial or total scapular aplasia, anomalies of the craniocer-vical junction, incomplete fusion of the posterior arches of the lumbar vertebrae, and flattened femoral heads. Distinguishing features in acrofacial dysostosis syndrome of Rodriguez (OMIM 201170), an early lethal disorder of autosomal recessive inheritance, include severe hypoplasia of the mandible, ischial bones, and shoulder girdle, complex limb anomalies (pre- and postaxial deficiencies), and cardiac and CNS malformations. This disorder shares similarities with Nager syndrome (OMIM 154400) and Genee-Wiedemann syndrome (OMIM 263750) (Rodriguez et al. 1990). Ischiadic hypoplasia with renal dysfunction, immunodeficiency, and polydactyly (OMIM 243340) comprises bilateral absence of the ischiadic ramus and tuberosi-ty (the acetabula are present), intrauterine growth retardation, microcephaly, craniofacial anomalies,hear-ing loss, hypospadias, cryptorchidism, hand and foot postaxial polydactyly, renal dysfunction, and hypogammaglobulinemia (Braegger et al. 1991). An association of ischial hypoplasia, tibial hypoplasia, and facial abnormalities (low-set ears, short nose with long philtrum, micrognathia, and cleft palate) has been described in a girl (Nishimura et al. 1998). Additional features included short stature, cervical spine anomalies, bowed lower legs, hypoplasia of the lesser trochanters, tibiofibular diastasis with malformed distal tibial epiphyses, clubfoot, and brachy-mesophalangy (Fig. 4.7).

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  • Lotta Koivisto
    What is hypoplastic appearance of the bone?
    4 years ago

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