The Fetal Skeleton (lesson 23) Flashcards
When can fetal limb buds be visualized?
8 wks
When do long bones fully develop?
7th to 12th wks
When do the bones in the hands and feet develop?
Between the 11th and 13th wk
The fetal long bones of the femur, humerus, radius, ulna, tibia, and fibula can be measured accurately when?
12 wks on
How much does the femur grow per week (between 14-27 wks)
3mm
In the third trimester, how much does the femur grow per week?
1mm
Of the Tibia and Fibula, what is the thicker of the two bones?
Tibia
Which way is the tibia and fibula orientated?
Tib - medial
Fib - lateral
What are the short-limbed dysplasias classified into? (4)
Rhizomelia, mesomelia, acromelia, micromelia
What is Rhizomelia?
Only the prox. portion is shortened
What is Mesomelia?
Shortening of the middle or intermediate segment
What is Acromelia?
Shortening of the distal portion
What is Micromelia?
Shortening of an entire extremity
What is cloverleaf deformity associated with?
Thanatophoric dysplasia
Lethal skeletal dysplasias are often accompanied by what?
Pulmonary hypoplasia
How can pulmonary hypoplasia be caused?
Oligiohydramnios, secondary to congenital disorders (thanatophoric dysplasia and asphyxiating thoracic dysplasia)
What is the most lethal skeletal dysplasia?
Thanatophoric dysplasia
Is Thanatophoric dysplasia more common in males or females
Males
What is the most common type of Thanatophoric Dysplasia?
Type I
What are the characteristics of Type I Thanatophoric Dysplasia?
- extreme rhizomelia
- bowed long bones
- normal trunk length
- platyspondyly
- frontal bossing
What are the characteristics of Type II Thanatophoric Dysplasia?
- straighter long bones
- taller vertebral bodies
- Kleeblattschadel (cloverleaf skull)
Where does the champagne cork appearance come from?
Thanatophoric Dysplasia
What is the most common nonlethal type of dwarfism?
Achondroplasia
What does Achondroplasia feature?
- rhizomelic limb bowing
- frontal bossing
- low nasal bridge
- trident hand
- macrocephaly
Why is Achondrogenesis lethal?
Due to pulmonary hypoplasia
What are the features of Type I (Parenti-Fraccaro) Achondrogenesis?
- extreme micromelia
- large head
- short and thin ribs (possibly fractured)
- poor ossification of the skull/spine/pelvic bones
What are the features of Type II (Langer-Saldino) Achondrogenesis?
- prominent forehead
- flat face with micrognathia
- absence of rib fractures
- less severe mineralization of fetal bones
- less severe micromelia
What is Osteogenesis Imperfecta? (OI)
Rare, inheritable connective tissue disorder caused by defects in type I collagen quality or quantity
Where is Type I collagen found?
Skin, ligaments tendons, and bone
What are some of the defects found in Type I OI pts?
- long bone and rib fractures
- blue sclera (eyes)
- hearing impairment
What type of OI is the most lethal?
Type II
What is the transparent bone sign?
Far side of the fetal long bone is visualized in addition to the near side
What is the most mild form of OI?
Type IV
What is congenital hypophosphotasia?
Rare inherited disease of defective bone mineralization
Is Type I or Type II Congenital Hypophosphotasia lethal?
Type I
What is Dysostosis?
Any condition characterized by abnormal ossification
What are two of the more common sonographically visualized types of Dysostosis?
Cleidocranial and craniofacial
When does examination of the fetal hands occur?
Late fist or mid-second trimester
A persistently clenched hand with overlapping index fingers is strongly associated with which Trisomy?
Trisomy 18 (Edwards)
A trident hand (three-pronged appearance) is typically found in which anomaly?
Achondroplasia
Preaxial polydactyly affects which side?
The radial side (thumb)
Postaxial polydactyly affects which side of the hand?
ulnar side (little finger)
Ready For Little Tiny Men - what are the sonographic features of dwarfism?
R hizomeloc limbs
F rontal bossing
L ow nasal bridge
T rident hand configuration
M acrocephaly/hydrocephaly
What is Acheiria?
absence of one or more hands
What is Apodia?
absence of one or more feet
What is Phocomelia?
Absence of the proximal portion of an extremity, with the hand or foot attached to the trunk
What is Meromelia?
absence of part of a limb
Aplasia or hypoplasia or which bone is common in many different syndromes?
Raidus
What is VACTERL?
Vertebrael anomaly
Anorectal atresoia
Cardiac anomalies
Trache
Esophageal fistula
Renal
Limb abnormalities
What is talipes?
Club foot, common birth defect where foot is more medial; bone of the foot lies in the same plane as the bone of the lower leg
What causes club foot?
Oligio, no room to move
What is ABS?
Amniotic band sequence
