The FetalSkeletal System

Carol B. Benson, MD

Ultrasound Assessmentof Fetal Skeletal System

Extremities

Spine

Calvarium

ExtremitiesAssess To Exclude

Size Skeletal dysplasia

Presence Absent limbAmniotic band

syndrome

Bones of forearms Radial hypoplasia

Hand position Clenched fists

Foot position ClubfootRockerbottom foot

Calderon Femur length

Michel arm 3 bones

Caraballo nl hand

No Disclosures

Foot

Femur Length

Normal for gestational age= Mean ± 2 SD

Femur length falls 2 - 4 SD below meanMost are growth restrictedWithout skeletal dysplasia

Femur length falls > 4 SD below meanUsually a skeletal dysplasiaBones appear abnormal by US

Steimle Femur length Long Bones are Too Short

Skeletal dysplasia

Dysotosis

Malformation

Deformationamniotic band syndromerestrictive uterine environment

Lethal Skeletal Dysplasias

Neonate cannot surviveusually due to respiratory failure

Ultrasound diagnosis typicallymade in 2nd trimester

Thanatophoric dysplasia Osteogenesis imperfecta Type 2 Achondrogenesis Congenital hypophosphatasia Short rib – polydactyly syndrome

Nonlethal Skeletal Dysplasias

Infants typically surviveUltrasound diagnosis typically

not made in 2nd trimestersometimes made in 3rd trimester

Heterozygous achondroplasia Osteogenesis imperfecta Types 1&4 Asphyxiating thoracic dystrophy

Ultrasound assessment

Degree of shortening of long bonestypically > 4 SD below mean for GA

Distribution of involved bonesextremities, spine, calvarium, ribs

Bony abnormalities

↓ mineralization, fractures, bowing

Polydactyly

Skeletal Dysplasias Thanatophoric Dwarf

Most common lethal skeletal dysplasiaSevere rhizomelia

(proximal shortening)Bowed long bonesNarrowed thorax – short ribsFlattened vertebral bodiesCloverleaf skullMegalencephaly – temporal lobe

with excess sulcation/fissures

Kristian 19wthanatophoric

Thanatophoric dysplasia

Kristian 19wthanatophoric

FEM

Osteogenesis ImperfectaType 2

Type 2 — Autosomal recessiveLethal

Ultrasound findings — Type 2FracturesDeformitiesPoor mineralizationSoft skull

Types 1, 3, & 4 — Autosomal dominantNonlethal

Lopez OI

Osteogenesis Imperfecta Type 2

Lopez OI

Osteogenesis Imperfecta Type 2

Astacio OI 3D

Osteogenesis Imperfecta Type 2

Osteogenesis ImperfectaType 1 & 4

Type 1 & 4 — Autosomal dominantNonlethal

Ultrasound findings — Type 1 & 4Lagging growth of long bones

3rd trimesterBowing of long bonesMild deformitiesPoor mineralizationSoft skull

McBride OI type 4

Osteogenesis Imperfecta Type 1

Al-Owfi OI type 4

Osteogenesis Imperfecta Type 4

Jones fem fxOI 4

Osteogenesis Imperfecta Type 4

2.4 cm 2.0 cm

18 weeks

Arthrogryposis

Multiple joint contracturesEtiologies

Limitation to movementOligohydramniosMultiple gestationBicornuate uterus

Abnormal nerve function Abnormal musculature Defective connective tissue

ArthrogryposisMultiplex Congenita

Ultrasound findingsContracturesFetal growth restrictionPolyhydramniosHydrops

Beausoleil arthrogryposis

Arthrogryposis

Eiresarthrogryposis

McGuiganarthrogryposis

Banerjee Larsen synarthrogryposis

Arthrogryposisfrom

Larsen syndrome(rare genetic syndrome)

Abnormal Hands & Forearms

Inherently abnormalMalformationDysplasia

Normal tissues effected by externalfactors

Deformationuterine constraintsamniotic band syndrome

Disruption (e.g., teratogen)

Radial Ray AnomaliesAssociated with

SyndromesCornelia de LangeFanconi anemiaHolt-OramRadial aplasia-ThrombocytopeniaPoland syndromeNager acrofacial dysostosisVACTERL

Trisomies 13 & 18

Henebry VACTERLabnl thumb

Radial Ray DefectAbnormal Thumb

VACTERL

Martins hypoplradius VACTERL

Hypoplastic radiusAbnormal thumb

VACTERL

Landry absent radius tri 18

Absent radiusLimb Reduction Defects

Terminal transverse deletions(e.g., absent hands)

Isolatedsporadic, unilateralamniotic band syndromevascular accident

SyndromesOrofacial (e.g., Poland)Amniotic bands

Penney absenttoes ABS Osgood absent hand

Osgood absent hand 3D bones

Nager Acrofacial Dysostosis

CharacteristicsMandibulofacial dysostosis

Hypoplastic mandibleExternal ear abnormalities± Auditory canal atresia

Upper extremity reduction defectsRadial ray defects

Alshamsi Nager’s

PolydactylySupernumerary fingers or toesSkeletal dysplasias

Short-rib polydactylyChondroectodermal dysplasiaAsphyxiating thoracic dysplasia

Trisomy 13Meckel-Gruber syndromeAutosomal dominant polydactyly

usually post-axial

MacGowan polydactyly withMeckel Gruber

Polydactyly with Meckel-Gruber

Hand Foot

IsabellePolydactyly

13 weeks 17 weeks

Polydactyly

TorresPolydactyly

Polydactyly

19 weeks

25weeks

Ectrodactyly

V-shaped defect (cleft) in middle ofhands &/or feet with missing digits

± Syndactyly Associated

Genetic syndromes, e.g.Split-hand-foot malformationSilver-RussellCornelia de Lange

Dowd ectrodacthands & feet

Appleton absent finger

Ligibel cleft handmissing finger

Clefthand

Clinodactyly &Overlapping Digits

Deviation or deflection of finger(s)

Curving of 5th finger towards 4th

Trisomy 21

Overlapping digitsTrisomy 13Trisomy 18

Subenko clinodactyly

Clinodactylyshort

middlephalanx

Normal

Sin abnl hands

Dixonclinodactyly

Clenched hands – Trisomy 18

Clubfoot

EtiologyGenetic

A variety of syndromesChromosomal defects

EnvironmentalSevere oligohydramniosUterine anomalies

Ultrasound findingsBones of the foot lie in parallel

to bones of lower leg

Lashley clubfeet

Clubfoot

21 weeks

13 weeks

Rockerbottom Foot

EtiologyTrisomy 18Skeletal dysplasia

Ultrasound findingsRounded bottom of foot

Woodlandrockerbottom feet

Rockerbottom feet – Trisomy 18

Atlas BRB rockerbottom feet

Rockerbottom feetAmniotic Band Syndrome

Early rupture of amnion

Fibrous bands entrap or adhere to fetus

Limb amputations or deformities

EncephalocelesFacial clefts

Ventral wall defectsEctopia cordis

Ultrasound Findings

Fetal deformitiesSkeletalCraniofacialVentral wall

Adherent bands

DDx: Amniotic “sheets”

Amniotic Band Syndrome

Dailey ABS anomalous hand

Amniotic BandSyndrome

Juris ABS missing hand

Amniotic BandSyndrome

13 weeks

21 weeks

Spinal Abnormalities

Meningomyelocele

Hemivertebra

Scoliosis

Diastomatomyelia

Caudal regression / sacral agenesis

Sacrococcygeal teratoma

Meningomyelocele

Normal

Meningomyelocele

GuilmetMeningomyelocele

Bardales tri 18Meningomyelocele

Meningocele

Spina bifida

Protrusion of membranes & fluid

No protrusion of nerve roots

Often skin covered

Ultrasound findingssplaying of posterior elementscystic mass protruding

Cabral 19w 3DMeningocele

19 weeks

Reif 20w Meningocele

Hemivertebrae

Associated with a variety of syndromes

Ultrasound findingsKink in spineMismatch of posterior

ossification centers

Johnson hemivertebrae

Hemivertebrae

Hazen Hemivert

Hemivertebrae

1

5

10

13

Rossman hemivert

Sacral Agenesis

Hypoplasia / absence2 or more sacral vertebrae

In fetuses of diabetic motherswith poor glucose control

MacDougall sacral agen

Sacral agenesis

Bensonsacral agenesis

Sacral agenesisCaudal Regression

Sacral agenesis + Anomalies of pelvis and lower extremities

In fetuses of diabetic motherswith poor glucose control

Kelshan caudal regression

Caudal regressionSacrococcygeal Teratoma

Germ cell tumor arisingin presacral area

Ultrasound findingsMass arising from lower sacrumExtending posteriorly and inferiorly± Hydrops± Extension anteriorly into pelvis

Bonica SCT

Sacrococcygeal TeratomaSacral erosion

Cranial Anomalies

Craniosynostosis Trigonocephaly (Trisomy 13) Cloverleaf skull (Thanatophoric

dysplasia)

Lemon sign (Chiari II malformation)

Strawberry skull (Trisomy 18)

Craniosynostosis

Premature closure of one or morecranial sutures; Male:Female = 2:1

Complications:Abnormal head shapeAbnormal facesNeurologic deficits

e.g., hearing lossPrenatal diagnosis

Typically not possible before 3rd trimester

Harrigan craniosyn

Craniosynostosis

26 weeks

Trigonocephaly

Craniosynostosis with premature

fusion of metopic suture

(anterior midline, forehead)

Associated with Trisomy 13

Britt tri 13trigonoceph

Trigonocephaly – Trisomy 13

35 weeksSemilobar

Holoprosencephaly

Cloverleaf Skull

Craniosynostosis causing

trilobed shape

prominent forehead

Associated with

Thanatophoric dysplasia

Cole thanat skull

Cloverleaf skull – Thanatophoric dysplasia

37 weeks

Lemon-Shaped Cranium

Associated with Chiari II malformationMeningomyelocele

Noguerialemon sign

Lemon Sign withMeningomyelocele

Strawberry-Shaped Cranium

Associated with Trisomy 18 Schindlerstrawb sk

Strawberry-Shaped CraniumTrisomy 18 – 15 weeks