The Fetal Skeleton (lesson 23)

Question 1

When can fetal limb buds be visualized?

Answer 1

8 wks

Question 2

When do long bones fully develop?

Answer 2

7th to 12th wks

Question 3

When do the bones in the hands and feet develop?

Answer 3

Between the 11th and 13th wk

Question 4

The fetal long bones of the femur, humerus, radius, ulna, tibia, and fibula can be measured accurately when?

Answer 4

12 wks on

Question 5

How much does the femur grow per week (between 14-27 wks)

Answer 5

3mm

Question 6

In the third trimester, how much does the femur grow per week?

Answer 6

1mm

Question 7

Of the Tibia and Fibula, what is the thicker of the two bones?

Answer 7

Tibia

Question 8

Which way is the tibia and fibula orientated?

Answer 8

Tib - medial
Fib - lateral

Question 9

What are the short-limbed dysplasias classified into? (4)

Answer 9

Rhizomelia, mesomelia, acromelia, micromelia

Question 10

What is Rhizomelia?

Answer 10

Only the prox. portion is shortened

Question 11

What is Mesomelia?

Answer 11

Shortening of the middle or intermediate segment

Question 12

What is Acromelia?

Answer 12

Shortening of the distal portion

Question 13

What is Micromelia?

Answer 13

Shortening of an entire extremity

Question 14

What is cloverleaf deformity associated with?

Answer 14

Thanatophoric dysplasia

Question 15

Lethal skeletal dysplasias are often accompanied by what?

Answer 15

Pulmonary hypoplasia

Question 16

How can pulmonary hypoplasia be caused?

Answer 16

Oligiohydramnios, secondary to congenital disorders (thanatophoric dysplasia and asphyxiating thoracic dysplasia)

Question 17

What is the most lethal skeletal dysplasia?

Answer 17

Thanatophoric dysplasia

Question 18

Is Thanatophoric dysplasia more common in males or females

Answer 18

Males

Question 19

What is the most common type of Thanatophoric Dysplasia?

Answer 19

Type I

Question 20

What are the characteristics of Type I Thanatophoric Dysplasia?

Answer 20

• extreme rhizomelia
• bowed long bones
• normal trunk length
• platyspondyly
• frontal bossing

Question 21

What are the characteristics of Type II Thanatophoric Dysplasia?

Answer 21

• straighter long bones
• taller vertebral bodies
• Kleeblattschadel (cloverleaf skull)

Question 22

Where does the champagne cork appearance come from?

Answer 22

Thanatophoric Dysplasia

Question 23

What is the most common nonlethal type of dwarfism?

Answer 23

Achondroplasia

Question 24

What does Achondroplasia feature?

Answer 24

• rhizomelic limb bowing
• frontal bossing
• low nasal bridge
• trident hand
• macrocephaly

Question 25

Why is Achondrogenesis lethal?

Answer 25

Due to pulmonary hypoplasia

Question 26

What are the features of Type I (Parenti-Fraccaro) Achondrogenesis?

Answer 26

- extreme micromelia - large head - short and thin ribs (possibly fractured) - poor ossification of the skull/spine/pelvic bones

Question 27

What are the features of Type II (Langer-Saldino) Achondrogenesis?

Answer 27

- prominent forehead - flat face with micrognathia - absence of rib fractures - less severe mineralization of fetal bones - less severe micromelia

Question 28

What is Osteogenesis Imperfecta? (OI)

Answer 28

Rare, inheritable connective tissue disorder caused by defects in type I collagen quality or quantity

Question 29

Where is Type I collagen found?

Answer 29

Skin, ligaments tendons, and bone

Question 30

What are some of the defects found in Type I OI pts?

Answer 30

- long bone and rib fractures - blue sclera (eyes) - hearing impairment

Question 31

What type of OI is the most lethal?

Answer 31

Type II

Question 32

What is the transparent bone sign?

Answer 32

Far side of the fetal long bone is visualized in addition to the near side

Question 33

What is the most mild form of OI?

Answer 33

Type IV

Question 34

What is congenital hypophosphotasia?

Answer 34

Rare inherited disease of defective bone mineralization

Question 35

Is Type I or Type II Congenital Hypophosphotasia lethal?

Answer 35

Type I

Question 36

What is Dysostosis?

Answer 36

Any condition characterized by abnormal ossification

Question 37

What are two of the more common sonographically visualized types of Dysostosis?

Answer 37

Cleidocranial and craniofacial

Question 38

When does examination of the fetal hands occur?

Answer 38

Late fist or mid-second trimester

Question 39

A persistently clenched hand with overlapping index fingers is strongly associated with which Trisomy?

Answer 39

Trisomy 18 (Edwards)

Question 40

A trident hand (three-pronged appearance) is typically found in which anomaly?

Answer 40

Achondroplasia

Question 41

Preaxial polydactyly affects which side?

Answer 41

The radial side (thumb)

Question 42

Postaxial polydactyly affects which side of the hand?

Answer 42

ulnar side (little finger)

Question 43

Ready For Little Tiny Men - what are the sonographic features of dwarfism?

Answer 43

R hizomeloc limbs F rontal bossing L ow nasal bridge T rident hand configuration M acrocephaly/hydrocephaly

Question 44

What is Acheiria?

Answer 44

absence of one or more hands

Question 45

What is Apodia?

Answer 45

absence of one or more feet

Question 46

What is Phocomelia?

Answer 46

Absence of the proximal portion of an extremity, with the hand or foot attached to the trunk

Question 47

What is Meromelia?

Answer 47

absence of part of a limb

Question 48

Aplasia or hypoplasia or which bone is common in many different syndromes?

Answer 48

Raidus

Question 49

What is VACTERL?

Answer 49

Vertebrael anomaly Anorectal atresoia Cardiac anomalies Trache Esophageal fistula Renal Limb abnormalities

Question 50

What is talipes?

Answer 50

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

Question 51

What causes club foot?

Answer 51

Oligio, no room to move

Question 52

What is ABS?

Answer 52

Amniotic band sequence