The Fetal Skeletal System

Transcription

1 The Fetal Skeletal System Ultrasound Assessment of Fetal Skeletal System Extremities Spine Calvarium Carol B. Benson, MD No Disclosures Extremities Assess To Exclude Size Skeletal dysplasia Presence Absent limb Amniotic band syndrome Bones of forearms Radial hypoplasia Hand position Clenched fists Foot position Clubfoot Rockerbottom foot Calderon Femur length Michel arm 3 bones Caraballo nl hand

2 Femur Length Foot Normal for gestational age = Mean ± 2 SD Femur length falls 2-4 SD below mean Most are growth restricted Without skeletal dysplasia Femur length falls > 4 SD below mean Usually a skeletal dysplasia Bones appear abnormal by US Steimle Femur length Long Bones are Too Short Skeletal dysplasia Dysotosis Malformation Deformation amniotic band syndrome restrictive uterine environment Lethal Skeletal Dysplasias Neonate cannot survive usually due to respiratory failure Ultrasound diagnosis typically made in 2 nd trimester Thanatophoric dysplasia Osteogenesis imperfecta Type 2 Achondrogenesis Congenital hypophosphatasia Short rib polydactyly syndrome Nonlethal Skeletal Dysplasias Infants typically survive Ultrasound diagnosis typically not made in 2 nd trimester sometimes made in 3 rd trimester Heterozygous achondroplasia Osteogenesis imperfecta Types 1&4 Asphyxiating thoracic dystrophy

3 Skeletal Dysplasias Ultrasound assessment Degree of shortening of long bones typically > 4 SD below mean for GA Distribution of involved bones extremities, spine, calvarium, ribs Bony abnormalities mineralization, fractures, bowing Polydactyly Thanatophoric Dwarf Most common lethal skeletal dysplasia Severe rhizomelia (proximal shortening) Bowed long bones Narrowed thorax short ribs Flattened vertebral bodies Cloverleaf skull Megalencephaly temporal lobe with excess sulcation/fissures Thanatophoric dysplasia Kristian 19w thanatophoric Kristian 19w thanatophoric FEM Osteogenesis Imperfecta Type 2 Type 2 Autosomal recessive Lethal Ultrasound findings Type 2 Fractures Deformities Poor mineralization Soft skull Types 1, 3, & 4 Autosomal dominant Nonlethal Osteogenesis Imperfecta Type 2 Lopez OI

4 Osteogenesis Imperfecta Type 2 Osteogenesis Imperfecta Type 2 Lopez OI Astacio OI 3D Osteogenesis Imperfecta Type 1 & 4 Type 1 & 4 Autosomal dominant Nonlethal Ultrasound findings Type 1 & 4 Lagging growth of long bones 3 rd trimester Bowing of long bones Mild deformities Poor mineralization Soft skull Osteogenesis Imperfecta Type 1 McBride OI type 4 Osteogenesis Imperfecta Type 4 Osteogenesis Imperfecta Type 4 Al-Owfi OI type 4 Jones fem fx OI 4 18 weeks 2.4 cm 2.0 cm

5 Arthrogryposis Multiple joint contractures Etiologies Limitation to movement Oligohydramnios Multiple gestation Bicornuate uterus Abnormal nerve function Abnormal musculature Defective connective tissue Arthrogryposis Multiplex Congenita Ultrasound findings Contractures Fetal growth restriction Polyhydramnios Hydrops Arthrogryposis Eires arthrogryposis Beausoleil arthrogryposis McGuigan arthrogryposis Arthrogryposis from Larsen syndrome (rare genetic syndrome) Banerjee Larsen syn arthrogryposis

6 Abnormal Hands & Forearms Inherently abnormal Malformation Dysplasia Normal tissues effected by external factors Deformation uterine constraints amniotic band syndrome Disruption (e.g., teratogen) Radial Ray Anomalies Associated with Syndromes Cornelia de Lange Fanconi anemia Holt-Oram Radial aplasia-thrombocytopenia Poland syndrome Nager acrofacial dysostosis VACTERL Trisomies 13 & 18 Radial Ray Defect Abnormal Thumb VACTERL Hypoplastic radius Abnormal thumb VACTERL Henebry VACTERL abnl thumb Martins hypopl radius VACTERL Absent radius Limb Reduction Defects Landry absent radius tri 18 Terminal transverse deletions (e.g., absent hands) Isolated sporadic, unilateral amniotic band syndrome vascular accident Syndromes Orofacial (e.g., Poland) Amniotic bands

7 Penney absent toes ABS Osgood absent hand Nager Acrofacial Dysostosis Osgood absent hand 3D bones Characteristics Mandibulofacial dysostosis Hypoplastic mandible External ear abnormalities ± Auditory canal atresia Upper extremity reduction defects Radial ray defects Alshamsi Nager s Polydactyly Supernumerary fingers or toes Skeletal dysplasias Short-rib polydactyly Chondroectodermal dysplasia Asphyxiating thoracic dysplasia Trisomy 13 Meckel-Gruber syndrome Autosomal dominant polydactyly usually post-axial

8 Polydactyly with Meckel-Gruber Polydactyly MacGowan polydactyly with Meckel Gruber Isabelle Polydactyly Hand Foot 13 weeks 17 weeks Polydactyly Ectrodactyly Torres Polydactyly 19 weeks 25 weeks V-shaped defect (cleft) in middle of hands &/or feet with missing digits ± Syndactyly Associated Genetic syndromes, e.g. Split-hand-foot malformation Silver-Russell Cornelia de Lange Dowd ectrodact hands & feet Appleton absent finger Ligibel cleft hand missing finger Cleft hand

9 Clinodactyly & Overlapping Digits Deviation or deflection of finger(s) Curving of 5 th finger towards 4 th Trisomy 21 Overlapping digits Trisomy 13 Trisomy 18 Subenko clinodactyly Clinodactyly short middle phalanx Normal Clenched hands Trisomy 18 Sin abnl hands Dixon clinodactyly Clubfoot Etiology Genetic A variety of syndromes Chromosomal defects Environmental Severe oligohydramnios Uterine anomalies Ultrasound findings Bones of the foot lie in parallel to bones of lower leg Lashley clubfeet 13 weeks 21 weeks Clubfoot

10 Rockerbottom Foot Rockerbottom feet Trisomy 18 Etiology Trisomy 18 Skeletal dysplasia Ultrasound findings Rounded bottom of foot Woodland rockerbottom feet Rockerbottom feet Atlas BRB rockerbottom feet Amniotic Band Syndrome Early rupture of amnion Fibrous bands entrap or adhere to fetus Limb amputations or deformities Encephaloceles Facial clefts Ventral wall defects Ectopia cordis Amniotic Band Syndrome Amniotic Band Syndrome Ultrasound Findings Fetal deformities Skeletal Craniofacial Ventral wall Adherent bands Dailey ABS anomalous hand DDx: Amniotic sheets

11 Amniotic Band Syndrome Spinal Abnormalities 13 weeks Juris ABS missing hand 21 weeks Meningomyelocele Hemivertebra Scoliosis Diastomatomyelia Caudal regression / sacral agenesis Sacrococcygeal teratoma Meningomyelocele Guilmet Meningomyelocele Normal Meningomyelocele Meningocele Bardales tri 18 Meningomyelocele Spina bifida Protrusion of membranes & fluid No protrusion of nerve roots Often skin covered Ultrasound findings splaying of posterior elements cystic mass protruding

12 19 weeks Cabral 19w 3D Meningocele Reif 20w Meningocele Hemivertebrae Hemivertebrae Associated with a variety of syndromes Ultrasound findings Kink in spine Mismatch of posterior ossification centers Johnson hemivertebrae Hemivertebrae 1 Hazen Hemivert 5 10 Rossman hemivert 13

13 Sacral Agenesis Sacral agenesis Hypoplasia / absence 2 or more sacral vertebrae MacDougall sacral agen In fetuses of diabetic mothers with poor glucose control Sacral agenesis Caudal Regression Benson sacral agenesis Sacral agenesis + Anomalies of pelvis and lower extremities In fetuses of diabetic mothers with poor glucose control Caudal regression Sacrococcygeal Teratoma Kelshan caudal regression Germ cell tumor arising in presacral area Ultrasound findings Mass arising from lower sacrum Extending posteriorly and inferiorly ± Hydrops ± Extension anteriorly into pelvis

14 Sacrococcygeal Teratoma Sacral erosion Cranial Anomalies Bonica SCT Craniosynostosis Trigonocephaly (Trisomy 13) Cloverleaf skull (Thanatophoric dysplasia) Lemon sign (Chiari II malformation) Strawberry skull (Trisomy 18) Craniosynostosis Premature closure of one or more cranial sutures; Male:Female = 2:1 Complications: Abnormal head shape Abnormal faces Neurologic deficits e.g., hearing loss Prenatal diagnosis Typically not possible before 3 rd trimester Harrigan craniosyn 26 weeks Craniosynostosis Trigonocephaly Trigonocephaly Trisomy 13 Craniosynostosis with premature fusion of metopic suture (anterior midline, forehead) Associated with Trisomy 13 Britt tri 13 trigonoceph 35 weeks Semilobar Holoprosencephaly

15 Cloverleaf Skull Craniosynostosis causing trilobed shape prominent forehead Associated with Thanatophoric dysplasia Cloverleaf skull Thanatophoric dysplasia Cole thanat skull 37 weeks Lemon-Shaped Cranium Associated with Chiari II malformation Meningomyelocele Nogueria lemon sign Lemon Sign with Meningomyelocele Strawberry-Shaped Cranium Strawberry-Shaped Cranium Trisomy weeks Associated with Trisomy 18 Schindler strawb sk