Diagnostic ultrasound ( PDFDrive )

1380 PART IV Obstetric and Fetal Sonography
A B C
D
E
F
G H I
FIG. 40.2 Normal Femur and Spectrum of Abnormal Appearances. (A) Normal femur: measure the longest length, excluding the proximal
and distal epiphyses and the specular relection of the lateral aspect of the distal femoral epiphysis (arrow). (B) Normal femur in the near ield,
with straight lateral border versus the curved medial border in the far ield of the transducer. (C) Isolated hypoplastic left femur (arrowhead), with
normal tibia (black arrow) and foot (white arrow). (D) Osteogenesis imperfecta type I. Isolated femoral fracture with acute angulation (arrow). (E)
Campomelic dysplasia. Mild shortening and a gently curved ventral femoral bowing (arrow). (F) Osteogenesis imperfecta type IIA. Bowed femur
with multiple discontinuities representing fractures. (G) Hypophosphatasia. Severe micromelia (relatively broad metaphysis, short diaphysis). (H)
Thanatophoric dysplasia. Curved, “telephone receiver” femur. (I) Chondrodysplasia punctata. Third-trimester appearance of a stippled epiphysis.
(C courtesy of Ants Toi, MD, University of Toronto; D and E courtesy of Shia Salem, MD, University of Toronto.)
abnormalities and serial measurements. A history of consanguinity
is important because many of the skeletal dysplasias have an
autosomal recessive mode of inheritance. Heterozygous achondroplasia,
the most common nonlethal skeletal dysplasia, has
an autosomal dominant pattern of inheritance. Family history
may not be helpful because 80% of cases are caused by a new
mutation.
Abnormal Bone Length or Appearance
he fetal femur is oten the only long bone routinely measured
at the second-trimester ultrasound evaluation. An abnormal FL
is traditionally deined as below 2 standard deviations (SD) for
gestational age. 25,26 Using this cutof, 2.5% of all fetuses would
be classiied as having short limbs. his exceeds the expected
frequency of skeletal dysplasias, and thus additional investigations
are needed to separate fetuses with a skeletal dysplasia from
those with no underlying pathology and those with other
diagnoses associated with growth restriction.
When one or all of the long bones measure less than 2 SD
for gestational age, a follow-up ultrasound should be done in 3
or 4 weeks to evaluate the interval growth. If the interval femur
growth is normal, there is a high likelihood that the fetus does