Diagnostic ultrasound ( PDFDrive )

1400 PART IV Obstetric and Fetal Sonography
he overall incidence of congenital limb reduction deformities
is estimated at 4 in 100,000 births. An isolated amputation may
be caused by amniotic band sequence, teratogen exposure,
or a vascular accident. he prenatal detection rate of isolated
limb reduction defect is estimated at 14.6%, compared to 49.1%
when associated anomalies are detected. 90 Terminal transverse
limb defects are associated with amniotic bands only in some
cases, and thus other causes (e.g., vascular disruption, fetal
hypoxemia, errors in embryologic development) are suspected in
other cases.
TABLE 40.9 Nomenclature of
Limb Anomalies
Anomaly
Description
LIMB REDUCTION ANOMALIES
Amelia
Absent limb
Adactyly
Absent digits
Acheiria
Absent hand
Apodia
Absent foot
Hemimelia
Absent extremity distal to
knee or elbow
Phocomelia
Absent middle segment of
limb
Ectrodactyly
Split hand
Ulnar or radial hemimelia Absent ulnar and ulnar digits
paraxial or radius and thumb
HAND AND FOOT ANOMALIES
Clinodactyly
Incurvature of a digit
Camptodactyly
Flexion of a digit
Syndactyly
Fusion of digits
Polydactyly
Extra digits
Oligodactyly
Decreased number of digits
Proximal Focal Femoral Deiciency
Proximal focal femoral deiciency is a rare, sporadic condition,
and 35% of those afected are infants of diabetic mothers 64 (see
Figs. 40.2C and 40.26). here is an asymmetrical degree of absence
of the subtrochanteric femur, which may extend to the femoral
head and acetabulum. 73 he femoral hypoplasia is oten associated
with ipsilateral ibular hemimelia, which may result in a bowed
appearance of the tibia, similar to that of campomelic dysplasia;
however, proximal focal femoral deiciency 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-ibula-ulnar
complex, which is nonfamilial, versus the femur-tibia-radius
complex, which has a strong genetic association. 91 When associated
with the unusual facies syndrome, the femoral hypoplasia
is usually bilateral.
Radial Ray Defects
Radial ray defects are associated with a wide variety of syndromes.
he 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. 40.27). here 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. Identiication
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. 40.28). Prenatal diagnosis is based on increased
chromosome breakage and sister chromatid exchange in cultured
amniotic luid cells, both before and ater exposure to
diepoxybutane. 92
FIG. 40.26 Isolated Femoral Hypoplasia at 20 Weeks. Note the downside left femur is short and curved.