Diagnostic ultrasound ( PDFDrive )

CHAPTER
40
The Fetal Musculoskeletal System
Phyllis Glanc, David Chitayat, and Sheila Unger
SUMMARY OF KEY POINTS
• Two-dimensional ultrasound is the primary imaging
modality for the majority of musculoskeletal disorders.
• When a fetal musculoskeletal dysplasia is suspected on
ultrasound, referral to a center with expertise may be
helpful.
• A main role of ultrasound is to determine if the condition is
likely lethal; it is important to use multiple parameters to
make this determination.
• After delivery or pregnancy termination, a diagnosis should
be established by a combination of clinical examination,
imaging, and molecular studies. Cell culture and DNA
banking are essential for molecular investigations. The
results should be reviewed with the parents to help in
their future reproductive plans.
CHAPTER OUTLINE
NORMAL FETAL SKELETON
Development
Extremity Measurements
SONOGRAPHIC EVALUATION OF
FETUS WITH SKELETAL
DYSPLASIA
Positive Family History
Abnormal Bone Length or
Appearance
Additional Diagnostic Techniques
Three-Dimensional Ultrasound
Radiography
Three-Dimensional Computed
Tomography
Magnetic Resonance Imaging
Molecular Diagnosis
LETHAL SKELETAL DYSPLASIAS
Thanatophoric Dysplasia
Achondrogenesis
Osteogenesis Imperfecta
Hypophosphatasia
Campomelic Dysplasia
Short-Rib Polydactyly Syndromes
Other Dysplasias
NONLETHAL OR VARIABLE-
PROGNOSIS SKELETAL
DYSPLASIAS
Heterozygous Achondroplasia
Diastrophic Dysplasia
Asphyxiating Thoracic Dysplasia
Ellis–van Creveld Syndrome
Chondrodysplasia Punctata
Dyssegmental Dysplasia
Osteogenesis Imperfecta Types I, III,
IV—Nonlethal Types
LIMB REDUCTION DEFECTS AND
ASSOCIATED CONDITIONS
Proximal Focal Femoral Deiciency
Radial Ray Defects
Amniotic Band Sequence
Caudal Regression Syndrome and
Sirenomelia
Arthrogryposis Multiplex Congenita
HAND AND FOOT MALFORMATIONS
SKELETAL FINDINGS ASSOCIATED
WITH ANEUPLOIDY
SUMMARY
Acknowledgments
Congenital bone disorders of the skeleton comprise a large
and heterogeneous group of disorders primarily afecting
the growth and development of the musculoskeletal system. he
prevalence of skeletal dysplasias, also called “osteochondrodysplasias,”
diagnosed prenatally or during the neonatal period,
excluding limb amputations, is 2.4 to 4.5 per 10,000 births. 1
here are three major categories: skeletal dysplasias, dysostoses,
and disruptions (Table 40.1). he number of recognized genetic
disorders with a substantial skeletal component is increasing,
and the distinction among dysplasias, metabolic bone disorders,
dysostoses, and malformation syndromes is constantly evolving.
he Nosology and Classiication of Genetic Skeletal Disorders
2015 revision recognizes 436 genetic bone disorders with a
substantial skeletal component 3-6 (Table 40.2).
Despite increased knowledge about the genetic origins of
many of these conditions and the improved ability to diagnose
and categorize these disorders correctly, the clinical and imaging
features remain a fundamental tool for diagnosing and directing
the molecular investigation. 3,7 Although many fetal skeletal
dysplasias can be accurately identiied by prenatal ultrasound,
this remains a challenging task because of the low incidence,
phenotypic variability, and wide range of appearances. 8 he
majority of cases have no family history of a similar condition.
Nonetheless, the majority of lethal skeletal dysplasias, and in
particular the most common—thanatophoric dysplasia, achondrogenesis,
and osteogenesis imperfecta type II—can be
diagnosed solely on the basis of prenatal ultrasound. 9 Tretter
et al. 10 determined that 26 of 27 lethal skeletal dysplasias were
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