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Chapter 40 ■ The Fetal Musculoskeletal System 1407
A B
C
The characteristic skeletal features of campomelic dysplasia are a short and ventrally bowed tibia and femur,
a hypoplastic or absent fibula, talipes equinovarus (clubfoot), and hypoplastic scapulae (Fig. 40-21). Bowing
may also occur in the upper extremities. Additional
skeletal features may include scoliosis; hypoplastic,
hypoplastic, or poorly ossified cervicothoracic vertebrae;
dislocated hips; 11 rib pairs; and facial abnormalities,
including micrognathia and cleft palate (Pierre Robin
sequence). Approximately 33% of fetuses have congenital heart disease (CHD) and brain (e.g., ventriculomegaly) and renal (e.g., pyelectasis) abnormalities.
Sex reversal is found in about 75% of the affected
46,XY cases, with a gradation of defects ranging from
ambiguous genitalia to normal female genitalia phenotype. The gene responsible for campomelic dysplasia
is expressed in the fetal brain, the testes, and the
perichondrium and chondrocytes of the long bones
and ribs.
62
Short-Rib Polydactyly Syndromes
Short-rib polydactyly dysplasias are a heterogeneous
group of rare and lethal skeletal dysplasias with an
autosomal recessive mode of inheritance. All forms are
characterized by severe micromelia and decreased thoracic circumference. The cranial vault measurements
and bone mineralization are normal. Polydactyly, cardiac,
and genitourinary abnormalities are found in most cases.
FIGURE 40-21. Campomelic dysplasia at 27 weeks.
A, Shortened femur and tibia with ventral bowing. B, Radiograph
confirms ventral bowing of the shortened tibia and femur.
C, Short and curved dysplastic scapula.
Thanatophoric dysplasia is distinguished by the absence
of polydactyly and the presence of the typical facial features, macrocrania, and platyspondyly. Ellis–van Creveld
syndrome (Fig. 40-22) and asphyxiating thoracic dystrophy have similar features, but the shortening of the
limbs and the narrowing of the thorax are less severe.
The short-rib polydactyly syndromes are subdivided
into four groups: type I—Saldino-Noonan; type II—
Majewski; type III—Verma-Naumoff; and type IV—
Beemer-Langer (which can occur without polydactyly).
60,63
Radiographic and clinical features can distinguish them.
The genetic basis remains unknown, and thus prenatal
diagnosis relies on ultrasound findings.
Fibrochondrogenesis is a rare, lethal, autosomal
recessive rhizomelic chondrodysplasia. The typical features include narrow chest (short ribs with cupping),
short long bones with irregular metaphyses with peripheral spurs, and extra-articular calcifications giving the
appearance of stippling, platyspondyly with decreased
ossification (particularly cervical vertebrae), and vertebral
midline clefts. Other features include flat facies and cleft
64,65
palate.
Other Dysplasias
Other lethal skeletal dysplasias include atelosteogenesis,
boomerang dysplasia, de la Chapelle dysplasia, and
Schneckenbecken dysplasia. These are rare and diffi-
cult to diagnose, specifically on ultrasound.
1408 PART IV ■ Obstetric Sonography
3
2
1
4
5
6
A
B C
D E F
FIGURE 40-22. Collage of polydactyly. A, Ellis–van Creveld syndrome. Postaxial polydactyly on cross section through six
digits. B, Corresponding radiograph shows postaxial polydactyly. Note hypoplastic distal phalanges and fusion of the third and fourth
metacarpals. C, Corresponding pathology specimen. D, Polydactyly may present as a soft tissue nubbin with no bony elements. E, Ellis–
van Creveld with toe polydactyly. F, 3-D ultrasound image shows isolated familial polydactyly.
NONLETHAL OR VARIABLEPROGNOSIS SKELETAL
DYSPLASIAS
trident configuration of the hand. The biparietal diameter (BPD) typically is above the 97th centile at term.
The interpedicular distances progressively narrow from
the upper to the lower lumbar spine. There is a progresThe nonlethal or variable prognosis skeletal dysplasias
form a larger group typically presenting with milder and
later onset of skeletal abnormalities. Select nonlethal or
variable-prognosis skeletal dysplasias with characteristic
ultrasound findings are described in Tables 40-5, 40-6,
and 40-7.
sive discrepancy between FL and BPD during the third
trimester, with FL falling below the first percentile com-
pared to BPD
67
(Fig. 40-23). This may occur as early as
21 weeks or as late as 27 weeks’ gestational age.
It is important to recognize that the pattern of BPD
greater than expected with FL less than expected for gestational age, in combination with average abdominal
Heterozygous Achondroplasia
Heterozygous achondroplasia is the most common
nonlethal skeletal dysplasia.
4
About 80% of cases are
the result of a spontaneous dominant mutation associated with advanced paternal age, and the remainder is
inherited from parental heterozygous achondroplasia.
The incidence is approximately 1 in 26,000 births. Previously considered a diagnosis of the third trimester,
recent studies have shown that a second-trimester diagnosis is possible.
66,67
The key features are mild to moderate forms of rhizomelic limb shortening (more prominent in upper
limbs), macrocranium, frontal bossing, depressed nasal
bridge, midface hypoplasia, and brachydactyly, with a
circumference measurements, suggests heterozygous
achondroplasia. A reliance on the mean of the three values
may result in an average value for gestational age, thus
masking the BPD/FL discrepancy. Patel and Filly
66
report
that fetuses with heterozygous achondroplasia have FL
that exceeds 34 mm at 26 weeks’ BPD age, whereas those
with homozygous achondroplasia do not. In cases where
both parents are heterozygous achondroplasia, fetal ultrasound can differentiate among normal, heterozygous, and
homozygous achondroplasia. Fetuses with FL below the
third percentile compared with the BPD at 17 weeks’
BPD age, with progressive shortening over the following
6 weeks, have homozygous achondroplasia, whereas those
with decreasing FL between 17 and 23 weeks’ BPD age
have heterozygous achondroplasia.
66
Chapter 40 ■ The Fetal Musculoskeletal System 1409
80
TABLE 40-5. RHIZOMELIC DYSPLASIA: KEY FEATURES
DYSPLASIA PROGNOSIS
Heterozygous achondroplasia Nonlethal Mild Progressive discrepancy in femur length and biparietal
Chondrodysplasia punctata,
rhizomelic form
Diastrophic dysplasia Variably lethal Mild-moderate Hitchhiker thumb, postural deformities, dislocations,
Lethal Moderate-severe Stippled epiphysis in third trimester
TABLE 40-6. MICROMELIC DYSPLASIA,
MILD: KEY FEATURES
DYSPLASIA PROGNOSIS
Asphyxiating
thoracic
dystrophy
Ellis–van Creveld
syndrome
May be lethal Long narrow thorax, renal
May be lethal Long narrow thorax,
KEY SONOGRAPHIC
FEATURES
anomalies (cystic dysplasia),
polydactyly (14%)
congenital heart disease
(50% atrial septal defect),
polydactyly (100%)
DEGREE OF LIMB
SHORTENING KEY SONOGRAPHIC FEATURES
diameter
joint contractures, clubfoot
TABLE 40-7. MICROMELIC DYSPLASIA,
MILD AND BOWED: KEY FEATURES
DYSPLASIA PROGNOSIS
Osteogenesis
imperfecta
type III
Campomelic
dysplasia
Nonlethal,
progressively
deforming
Variably lethal Ventral-bowing femur and
KEY SONOGRAPHIC
FEATURES
Lower extremities demonstrate
greater degree of shortening
and fractures/bowing
tibia, hypoplastic or absent
fibula, hypoplastic scapulas
72
64
56
48
40
Femur length (mm)
32
24
16
22 30 38 46 54 62 70 78 86 94
Biparietal diameter (mm)
Upper 99% CL
Lower 99% CL
FIGURE 40-23. Femur length (FL) versus biparietal
diameter (BPD). Seven cases of recurrent heterozygous
achondroplasia. The FL falls below the 99% confidence limit
(CL) by the time the BPD corresponds to 27 weeks’ gestational
age (~69 mm). (From Kurtz AB, Filly RA, Wapner RJ, et al. In
utero analysis of heterozygous achondroplasia: variable time of onset
as detected by femur length measurements. J Ultrasound Med
1986;5:137-140.)
The identification of the gene responsible for achondroplasia, FGFR3, mapped to the short arm of chromosome 4, has allowed the early prenatal diagnosis by DNA
analysis by CVS when the parents are heterozygous for
achondroplasia.
51
Diastrophic Dysplasia
Diastrophic dysplasia is an autosomal recessive disorder
with variable expression and a predominantly rhizomelic
form of micromelia. The term diastrophic implies
“twisted,’’ which reflects the multiple postural deformities, dislocations, joint contractures, and kyphoscoliosis
present.
1
The most characteristic feature is the “hitchhiker thumb,’’ caused by a lateral positioning of the
thumb in association with a hypoplastic first metacarpal
(Fig. 40-24). The first toe may have similar positioning.
There is a severe talipes equinovarus (clubfoot), which
may be refractory to surgical treatment. Other features
include micrognathia, cleft palate (50%), and laryngotracheomalacia. The life span may be normal if the
progressive kyphoscoliosis does not compromise cardiopulmonary function. The diastrophic dysplasia gene was
mapped to the long arm of chromosome 5 and found to
encode a novel sulfate transporter. Mutations in the
same gene were reported in ACH1B and atelosteogenesis
type II.
68,69
Asphyxiating Thoracic Dysplasia
Asphyxiating thoracic dysplasia, or Jeune syndrome, is
an autosomal recessive disorder with variable expressivity. The incidence is 1 in 70,000 to 130,000 births. The
perinatal mortality is high as a result of pulmonary hypoplasia. Those who survive may develop renal and hepatic
1,68
fibrosis
(see Table 40-7). Key features are a mild to
1410 PART IV ■ Obstetric Sonography
Thumb
FIGURE 40-24. Diastrophic dysplasia with “hitch-
hiker thumb.” (Courtesy Fetal Assessment Unit, University
Health Network.)
moderate form of micromelia (60%) with rhizomelic
predominance, a long narrow thorax with short horizontal ribs, inverted “handlebar” appearance of the clavicles,
renal dysplasia and cysts, and postaxial polydactyly
in 14%.
Ellis–van Creveld Syndrome
Ellis–van Creveld syndrome, or chondroectodermal
dysplasia, is an autosomal-recessive disorder with an
incidence of 1 per 150,000 births. The condition has a
high prevalence among inbred populations, such as the
Amish and the Arabs of the Gaza strip.
a nonlethal disorder, but death can result from pulmonary hypoplasia.
33,60
Key features include mild to moderate form of micromelia with a mesomelic predominance,
short horizontal ribs, postaxial or ulnar polydactyly
Fig. 40-22) that is almost 100% in the hands and 25%
in the feet,
52
and CHD (50%), most often atrial septal
60
It is generally
1
(see
defect. Additional findings include a progressive distalward shortening of the extremities with hypoplastic
distal phalanges. Fusion of the metacarpals and phalanges is common. The presence of polydactyly, CHD, and
the absence of renal cysts help to distinguish this condition from asphyxiating thoracic dystrophy.
Chondrodysplasia Punctata
Chondrodysplasia punctata, or stippled epiphyses, is a
heterogeneous group of disorders with many small calcifications (ossification centers) in the cartilage, in the
ends of bones, and around the spine. Known associated
conditions include single-gene disorders such as rhizo-
FIGURE 40-25. Chondrodysplasia punctata, rhizo-
melic form. Radiograph demonstrates stippled calcification
within the epiphyseal and paravertebral cartilages. Humeri are
very short, the femurs are relatively short.
melic chondrodysplasia punctata, Conradi-Hünermann
syndrome, and Zellweger syndrome (cerebrohepatorenal
syndrome); chromosomal abnormalities such as trisomy
21 and 18; maternal autoimmune diseases; and teratogen
exposure (e.g., warfarin, alcohol).
70,71
Rhizomelic chondrodysplasia punctata is an autosomal-recessive condition caused by a peroxisomal disorder
that appears as severe, symmetrical, predominantly rhizomelic limb shortening.
60,72
The incidence is approximately 1 in 110,000 births, and it is generally lethal
before the second year of life. The humeri tend to be
relatively shorter than the femurs and have metaphyseal
cupping. The enlarged epiphyses with characteristic stippling may occasionally be identified on ultrasound in the
third trimester (Fig. 40-25; see also Fig. 40-2, I). Other
abnormalities include dysmorphic facial features, joint
contractures, coronal clefting of the vertebral bodies,
brain abnormalities, and severe mental retardation.
Conradi-Hünermann syndrome, or the nonrhizo-
melic form of chondrodysplasia punctata (CDPX2), is
an X-linked dominant condition with extreme phenotypic variations, rendering the antenatal diagnosis difficult in the absence of known family history. The widely
variable phenotypic presentation may be related to
random X inactivation.
73,74
CDPX2 is uncommon, with
X-linked dominant inheritance and possible lethality in
73
the hemizygous male (Xp11).
The characteristic skeletal abnormalities are asymmetrical shortening of the
extremities with punctate calcifications primarily affecting the ends of long bones, the carpal and tarsal regions,
paravertebral region, and pelvic bones. Stature is usually
reduced; kyphoscoliosis with shortening of the long
bones (particularly femur and humerus) and dysmorphic
facial features are common.
71
Dyssegmental Dysplasia
Dyssegmental dysplasia is a rare autosomal recessive skeletal dysplasia characterized by gross vertebral disorganization. The findings typically include micromelia, short
narrow thorax, joint rigidity, anisospondyly (gross
irregularity of the size and shape of the vertebral bodies)
which may include malsegmentation, clefting or “oversize” bodies, kyphoscoliosis, and multiple ossification
centers (Fig. 40-26). The gross spine disorganization
may be recognized as early as the first trimester. The
more severe form is referred to as Silverman-Hand-
maker and the milder form as Rolland-Desbuquois,
although some think that dyssegmental dysplasia may
represent a spectrum of findings caused by different
mutations in the perlecan gene.
75
Chapter 40 ■ The Fetal Musculoskeletal System 1411
Osteogenesis Imperfecta Types
I, III, IV—Nonlethal Types
Osteogenesis imperfecta type I is a mild, “tarda’’ variant
inherited in an autosomal dominant manner as a result
of mutation in the COL1A1 (on chromosome 17) or
COL1A2 (on chromosome 7) and possibly in other collagen genes. OI type I is a generalized connective tissue
disorder characterized by bone fragility and blue sclerae.
The bones are of normal length, and only 5% present at
birth with fractures. Most fractures occur from childhood to puberty. There is progressive hearing loss in
approximately 50% of type I cases. Type III has a het-
erogeneous mode of inheritance. This is a nonlethal,
progressively deforming variety of OI that often spares
the humeri, vertebrae, and pelvis. Rib involvement is
variable. The blue sclerae will normalize, and there is no
associated hearing impairment. Type IV is an autosomal
dominant form of OI. It is the mildest form, involving
isolated fractures. The sclerae are blue at birth but
normalize over time. There is no associated hearing
impairment.
LIMB REDUCTION DEFECTS AND
ASSOCIATED CONDITIONS
FIGURE 40-26. Dyssegmental dysplasia in stillborn
fetus. AP radiograph demonstrates anisospondyly, character-
ized by the varying size and shape of vertebral bodies. The “oversize” large vertebral bodies are characteristic. Note the shortened,
wide, and angulated tubular long bones with a characteristic
dumbbell configuration. Small thorax with short ribs is associated
with pulmonary hypoplasia.
This heterogeneous group of disorders is associated with
a spectrum of limb defects caused by chromosomal
abnormalities, single-gene disorders, and maternal exposures and diseases, causing a variety of limb defects.
There are three major categories of limb reduction
defects. A malformation is a defect resulting from an
abnormal developmental process. A deformation is an
abnormality of form, shape, or position caused by
mechanical forces. A disruption is a defect caused by the
extrinsic breakdown or interference with an originally
normal developmental process. The defect can consist of
the absence of an entire limb (amelia), of part of a limb
(phocomelia), or of digits (oligodactyly), or it can
involve an increased number of digits (polydactyly).
76
It can also affect only the radial ray or ulnar ray, with
or without involvement of the corresponding fingers
(Table 40-8).
The overall incidence of congenital limb reduction
deformities is estimated at 0.40 per 10,000 births. An
isolated amputation may be caused by amniotic band
sequence, teratogen exposure, or a vascular accident.
Overall limb abnormalities are detected prenatally in
approximately 45% of cases diagnosed postnatally.
77
Proximal Focal Femoral Deficiency
Proximal focal femoral deficiency is a rare, sporadic condition, and 35% of those affected are infants of diabetic
mothers
52
(see Fig. 40-2, C ). There is an asymmetrical
degree of absence of the subtrochanteric femur, which
1412 PART IV ■ Obstetric Sonography
TABLE 40-8. NOMENCLATURE OF LIMB
ANOMALIES
ANOMALY DESCRIPTION
Amelia Absent limb
Adactyly Absent digits
Acheiria Absent hand
Apodia Absent foot
Hemimelia Absent extremity distal to knee
Phocomelia Absent middle segment of limb
Ectrodactyly Split hand
Ulnar or radial hemimelia Absent ulnar and ulnar digits
Clinodactyly Incurvature of a digit
Camptodactyly Flexion of a digit
Syndactyly Fusion of digits
Polydactyly Extra digits
Oligodactyly Decreased number of digits
Limb Reduction Anomalies
or elbow
paraxial or radius and thumb
Hand and Foot Anomalies
may extend to the femoral head and acetabulum.60 The
femoral hypoplasia is often associated with ipsilateral
fibular hemimelia, which may result in a bowed appearance of the tibia, similar to that of campomelic dysplasia;
however, proximal focal femoral deficiency is generally
unilateral. Hypoplasia or aplasia of other long bones,
vertebral anomalies, microcephaly, and facial dysmorphism can also occur. If the defect is unilateral, it may
represent the femur-fibula-ulnar complex, which is
nonfamilial, versus the femur-tibia-radius complex,
which has a strong genetic association.
78
When associated with the unusual facies syndrome, the femoral
hypoplasia is usually bilateral.
Caudal Regression Syndrome
and Sirenomelia
Caudal regression syndrome consists of partial to complete sacral agenesis and abnormalities of the lumbar
spine, pelvis, and lower limbs.
79-81
The majority of cases
are associated with maternal diabetes, but familial cases
have been reported. Sirenomelia is characterized by an
absent sacrum, fusion of the lower extremities, anorectal
atresia, and renal dysgenesis or agenesis (Fig. 40-27).
Severe oligohydramnios and single umbilical artery are
typically present. Prevalence is approximately 1:60,000
births.
Amniotic Band Sequence
Amniotic band sequence is suspected to be secondary to
first-trimester rupture of the amnion, resulting in amni-
otic bands that extend from the chorionic surface of
the amnion to the fetal tissue.
82,83
The incidence is
approximately 1:1200 live births but is much higher in
spontaneous abortions. Depending on the timing and
orientation of the bands, the resultant disruption of fetal
organs includes amputations of limbs or digits (Figs.
40-28 and 40-29), bizarre facial or cranial clefting, and
thoracoabdominal schisis. The distribution is asymmetrical. Constriction ring defects are the most common
finding. Fibrous bands of tissue with a constricting ring
and distal elephantiasis or protrusion of uncovered bone
distally are pathognomonic for this anomaly (Fig. 40-30).
Antenatally, an aberrant band attached to the fetus,
with characteristic deformities and restriction of motion,
permits the diagnosis. An amniotic sheet is a synechia,
or scar in the uterus, and is distinguished from an amniotic band by a thickened base and a free edge.
84
Syn-
echiae are not associated with amniotic band sequence.
The limb–body wall complex is a sporadic disorder
that occurs in approximately 1:4000 live births with a
similar, but more severe and lethal, complex of fetal
malformations.
85
Additional findings include evisceration of internal organs, myelomeningocele, marked scoliosis, and short straight umbilical cord.
Limb Reduction Defects
The prenatal detection rate of isolated limb reduction
defect is estimated at 14.6%, compared to 49.1% when
associated anomalies were detected.
86
Terminal trans-
verse limb defects are associated with amniotic bands
only in some cases, and thus other etiologies (e.g., vascular disruption, fetal hypoxemia, errors in embryologic
development) are suspected in other cases.
Radial Ray Defects
Radial ray defects are associated with a wide variety of
syndromes. The diagnosis is based on the absence of a
visualized distal radius at the same level as the ulna, in
association with a radial deviation or clubhand (Fig.
40-31). There may be bowing or hypoplasia of the ulna
and a hypoplastic or absent thumb. Ulnar ray defects
are rare.
Fanconi pancytopenia (syndrome) is an autosomal
recessive blood dyscrasia in which 50% of cases have an
associated unilateral or bilateral aplastic or hypoplastic
thumb and radius. Identification of the thumb hypoplasia or aplasia in association with a radial ray defect
suggests this diagnosis, initiating discussion of prenatal
diagnosis and potential cesarean section to avoid excessive bleeding (Fig. 40-32). Prenatal diagnosis is based on
increased chromosome breakage and sister chromatid
exchange in cultured amniotic fluid cells, both before
and after exposure to diepoxybutane.
87
Aase syndrome is an autosomal recessive blood
dyscrasia characterized by hypoplastic anemia, a hypoplastic distal radius with radial clubhand, and a
triphal-
angeal thumb. Associated cardiac defects (ventricular
septal defect, coarctation of aorta) may be present.
Chapter 40 ■ The Fetal Musculoskeletal System 1413
A
B
FIGURE 40-27. Sirenomelia. A, Cross section of lower extremities. Femurs (arrows) are closer than expected because of fusion of
the overlying soft tissues with a continuous layer of overlying skin (arrowheads). B, Sacral agenesis with abrupt termination of the lower
spine (arrow). C, Single, fused lower extremity and sacral agenesis.
Triphalangeal thumb may also be found in Holt-Oram
syndrome, Diamond-Blackfan syndrome, chromosomal
abnormalities, and fetal hydantoin exposure.
C
association, acrorenal syndrome, Cornelia de Lange syndrome, Goldenhar syndrome, Nager acrofacial dysostosis, and Klippel-Feil syndrome.
Thrombocytopenia–absent radius syndrome (TAR)
is an autosomal recessive blood dyscrasia characterized
by hypomegakaryocytic thrombocytopenia and bilateral
absence of the radii.
88
The thumb is always present. The
humerus and lower extremities are variably involved.
One third of such patients have CHD, typically tetralogy
of Fallot or septal defects. Fetuses are at risk of intracranial hemorrhage, so delivery by cesarean section is
recommended (Fig. 40-33).
Holt-Oram syndrome is an autosomal dominant disorder consisting of a congenital heart defect (atrial or
ventricular septal defect) in combination with a variety
of upper limb anomalies. The limbs are asymmetrically
affected, with the left limb usually showing more effects
than the right. The lower extremities are not involved.
Roberts’ syndrome, or pseudothalidomide syndrome,
is an autosomal recessive disorder characterized by tetraphocomelia and bilateral cleft lip/palate. The limb reductions are most prominent in the upper extremities.
Other conditions associated with radial ray abnormalities include trisomies 18 and 13, the VACTERL
Arthrogryposis Multiplex Congenita
Arthrogryposis multiplex congenita is a heterogeneous
group of disorders with multiple joint contractures of
prenatal onset
89
(Fig. 40-34). Normal fetal motion by
approximately 7 to 8 weeks onward is required for development of the musculoskeletal system. Some cases result
from extrinsic causes, such as oligohydramnios, twinning, or uterine masses, and most of these have a good
prognosis. Intrinsic causes include neuromuscular disorders (most cases) and skeletal and connective tissue disorders. Typically, the severity of the deformity increases
distally, with maximal deformity in the hands and feet.
This may result in the “Buddha position” of the fetus,
with arms and legs crossed and ending in clubhand or
clubfoot (Fig. 40-34, D). The fetal akinesia sequence
refers to the combination of multiple joint contractures
in association with IUGR, underdevelopment of the
bones, pulmonary hypoplasia, typical craniofacial abnormalities, and a short umbilical cord.
1414 PART IV ■ Obstetric Sonography
FIGURE 40-28. Amputation of the hand. Upper extremity
ends abruptly distal to the wrist, in the midcarpal region (arrows).
(Courtesy Ants Toi, MD, University of Toronto.)
A B
C
FIGURE 40-29. Amputation of right lower extrem-
ity. A, Ultrasound image demonstrates abrupt ending of the right
lower limb (arrow). B, Comparison ultrasound image shows normal
left lower limb. C, T2-weighted MR image confirms amputation of
the right lower limb (arrow).
Chapter 40 ■ The Fetal Musculoskeletal System 1415
BA
DC
FIGURE 40-30. Amniotic band sequence. Constriction rings with distal elephantiasis. A, Ultrasound lateral image of the
distal forearm and hand demonstrates the two constriction rings with elephantiasis. B, Ultrasound of the digits demonstrates the distal
tapering of the digits. C, Radiograph demonstrates the two constriction rings in the distal forearm and hand. D, Correlative specimen
photograph.
Limb pterygium, or webbing of the skin across a
joint, can involve a single or several joints
90
and etiologically is a heterogeneous disorder. Popliteal pterygium is
the most common dominantly inherited pterygium
syndrome.
Asymmetrical limb enlargement may be caused by
hemihypertrophy, cutaneous hemangioma or lymphangioma, elephantiasis secondary to a constricting band,
arteriovenous malformations, neurofibromatosis, or
Beckwith-Wiedemann syndrome. Hereditary lymph-
edema type 1, or Nonne-Milroy lymphedema, is a rare
autosomal dominant condition secondary to deficient
lymphatic drainage, typically affecting the lower extremities. The subcutaneous tissues of the affected extremity
appear diffusely thickened. Associated ascites and pleural
effusions may be seen. There is variable expressivity and
age of onset
91
(Fig. 40-35). Extremity enlargement may
also be related to thickened subcutaneous tissues, as in
hydrops or large-for-gestational-age infants.
Kyphoscoliosis may be a manifestation of an isolated
vertebral defect or may be associated with myelomeningocele or with complex syndromes, such as
VACTERL, limb–body wall complex, neurofibromatosis, arthrogryposis, diastrophic dysplasia, and other skeletal dysplasias.
HAND AND FOOT DEFORMITIES
A complete digit evaluation can be performed by 12 to
13 weeks’ gestation.
hands with digit extension in the first half of gestation,
92
The fetus typically maintains open
FIGURE 40-31. Radial ray anomaly diagnosed at
13 weeks’ gestation. Three-dimensional (3-D) ultrasound
surface display demonstrates the hypoplastic radius and ulna in
association with talipomanus (clubhand) (arrow).
whereas in the second half the fetus may maintain
hand closure for relatively prolonged periods, up to 30
minutes, limiting detailed evaluation. The incidence of
finger abnormalities is approximately 1:1000 fetuses, of
which 60% will have either an associated malformation
sequence or karyotypic malformation. The optimal time
for evaluation of the hands and feet is during the second
trimester.
12,93-95
1416 PART IV ■ Obstetric Sonography
HAND
ULN
HUM
A
C
FIGURE 40-32. Fanconi pancytopenia. Radial ray aplasia with talipomanus and bilateral absence of thumbs. A, Radial
deviation left hand, or clubhand, secondary to radial ray aplasia and ulnar hypoplasia. Note absent thumb. B, More extreme example of
radial deviation hand or clubhand secondary to radial ray aplasia and ulnar hypoplasia. C, Correlative radiograph (of A) of left arm. Note
absent thumb. D, Correlative specimen photograph of A. Note absent thumb. (Courtesy Shia Salem, MD, University of Toronto.)
B
D
Transient findings represent a potential pitfall in the
analysis of the distal extremities. During the second half
of gestation, the fetus may appear to have pseudosyn-
dactyly by maintaining clenched fists for prolonged
periods or the appearance of “sandal foot.” The diagnosis
of an isolated clubfoot can be risky because the fetus can
hold the foot in a position to suggest the diagnosis in the
absence of a structural defect. An apparent clubfoot may
be secondary to positioning against the maternal uterine
wall or in the setting of oligohydramnios, which subsequently resolves with a change in fetal position or amniotic fluid volume.
Aneuploidy is associated with an increased risk of
hand and foot anomalies, including persistent clenched
hand, overlapping digits, clinodactyly, polydactyly, syndactyly, simian creases, talipes equinovarus, rockerbottom foot, and sandal toes (Fig. 40-36).
Persistent clenched hand with overlapping of digits
occurs in more than 50% of trisomy 18 fetuses and is
generally bilateral. This characteristic hand appearance
is highly suggestive of trisomy 18 but can also occur in
other conditions, such as fetal akinesia syndrome and
triploidy.
Clinodactyly is the permanent incurvature of a finger.
Clinodactyly, caused by asymmetric hypoplasia of the
middle phalanx (medial shorter than lateral aspect), most
often involves the fifth finger and is associated with trisomies 13, 15, 18, and 21 (Fig. 40-36, G). Clinodactyly
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