Ch 13 Skeleton Flashcards

1
Q

Fetal limb buds are seen as early as how many weeks by EV?

A

8 weeks (lower buds seen before upper buds)

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2
Q

Long bones fully develop during what weeks?

A

During 7-12 weeks

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3
Q

Bones in hands + feet are developed b/w what weeks?

A

11-13 weeks

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4
Q

The long bones of the femur, humerus, rad/uln + tib/fib can be accurately measured from what week onward?

A

12 weeks on

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5
Q

Which femur should we measure?

A

The most anterior one

(posterior femur looks artifactually bowed + shortens our length inaccurately)

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6
Q

The femur grows how many mm per week?

A

14-27 weeks: 3mm per week
3rd trimester: 1mm per week

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7
Q

Femur length varies depending on what maternal factors?

A

Maternal height, weight + ethnicity

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8
Q

Is the tibia or fibula thicker?

A

Tibia

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9
Q

Location of tib/fib?

A

Tib: medial
Fib: lateral

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10
Q

Is the radius or ulna longer?

A

Ulna

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11
Q

Location of rad/uln?

A

Rad: thumb side (lateral)
Uln: pinky side (medial)

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12
Q

How many independent digits do the hands have?

A

5 - they vary lengths

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13
Q

How many phalanges does each hand digit have?

A

3

(thumb only has 2)

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14
Q

Is a constantly fixed hand position abnormal?

A

Yes - should always be seen in flexion + extension

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15
Q

How many tarsal bones + digits are there in the foot?

A

5

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16
Q

How many phalanges does each foot digit have?

A

2

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17
Q

Why can the foot measurement be used to determine gest age?

A

B/c it has a characteristic pattern of normal growth

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18
Q

What is skeletal dysplasia?

A

-Abnormal development of cartilaginous + osseous tissues
-Results in bones that appear short, thin, deformed or that fail to forma at all

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19
Q

Is diagnosing skeletal dysplasia hard?

A

Yes - should document + image each limb at the start of the exam when scanning an at-risk fetus

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20
Q

How do the long bones appear with skeletal dysplasia?

A

-May be shorter
-Must evaluate for bowing + fractures

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21
Q

What are the 4 categories of short-limbed dysplasias?

A

Rhizomelia: prox part is shortened
Mesomelia: middle part is shortened
Acromelia: distal part is shortened
Micromelia: entire extremity is shortened

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22
Q

What other abnormalities should be noted when assessing for skeletal dysplasia?

A

-Abnormal # of digits + fluid volumes
-Facial or cardiac defects
-Skull shape (cloverleaf deformity)

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23
Q

Lethal skeletal dysplasias are often accompanied by what?

A

Pulmonary hypoplasia

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24
Q

What is the m/c form of lethal skeletal dysplasia?

A

Thanatophoric dysplasia (TD)

(thanatophoric = death bearing in greek)

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25
Q

Is TD m/c in males or females?

A

Males

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26
Q

2 types of TD?

A

Type 1 (m/c):
-extreme rhizomelia (prox) + normal trunk length
-bowed long bones (telephone receiver)
-platyspondyly (widened vertebral bodies)
-frontal bossing (forehead)

Type 2:
-straighter long bones
-taller vertebral bodies
-kleeblattschadel (cloverleaf skull)

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27
Q

What is the ā€œchampagne cork appearanceā€ associated with?

A

TD - is a narrow thorax with a protruding abdomen

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28
Q

How is the prognosis for TD?

A

Poor - m/c stillborn or die after birth due to pulmonary hypoplasia

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29
Q

What is the m/c nonlethal type of dwarfism?

A

Achondroplasia

(occurs equally in M/F)

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30
Q

Features of achondroplasia?

A

-Rhizomelic limb bowing (prox part)
-Frontal bossing
-Low nasal bridge
-Trident hand (increased space b/w 3rd/4th digit)
-Macro + hydrocephaly

31
Q

How is the prognosis with achondroplasia?

A

Good - orthopaedic problems are only concern

32
Q

What is achondrogenesis?

A

Rare + lethal skeletal dysplasia

(lethal b/c of pulmonary hypoplasia)

33
Q

2 types of achondrogenesis?

A

Type 1: parenti-fraccaro
-extreme micromelia
-lg head
-short/thin ribs
-poor ossification of skull, spine + pelvic bones

Type 2: langer-saldino
-prominent forehead
-flat face with micrognathia
-absent rib fractures
-less severe mineralization of fetal bones
-less severe micromelia

34
Q

What is osteogenesis imperfecta (OI)?

A

Rare inheritable connective tissue disorder, due to defects in type 1 collagen quality/quantity

(type 1 collagen is found in skin, ligaments, tendons + bones)

35
Q

A defect in type 1 collagen leads to what?

A

Decreased mineralization of bone + bone fragility found in ptā€™s with OI

Causes:
-long bone + rib fractures
-blue sclera
-hearing impairment

36
Q

How many types of OI are there?

A

4

37
Q

What is type 1 OI?

A

-Due to abnormal decrease in quantity of collagen produced (milder disease)
-Most fractures donā€™t appear until after birth
-Normal stature + good prognosis

38
Q

What is type 3 OI?

A

-Autosomal dominant or recessive
-Less severe than type 2 in utero
-Limb bowing in utero
-Multiple fractures at birth

39
Q

List the types of OI from least to most severe?

A

Type 4 (dominant), type 1 (doesnā€™t say), type 3 (either) + type 2 (recessive)

40
Q

What is type 4 OI?

A

-Mildest form of disease
-Does not present until later in life
-Inherited in autosomal dominant pattern
-Not common to be detected prenatally
-May only see short stature or premature osteoporosis later in life

41
Q

What is type 2 OI?

A

-Most severe form + inherited in recessive fashion
-Transparent bone sign (far side of long bone is visualized in addition to near side)
-Poor prognosis, deadly
-Reduced echogenicity + thicker bones
-Concave ribs from fractures
-Bell shaped throax
-Skull lacks ossificaiton (can compress with probe)

42
Q

What is camptomelic dysplasia?

A

Rare form of short limbed dwarfism, transmitted in autosomal dominant fashion

(poor prognosis, most die)

43
Q

Camptomelic dysplasia is characterized by what?

A

-Short + bowed limbs
-Short trunk
-Large head
-Bell shaped chest

(slide images are pointing to scapula)

44
Q

What is congenital hypophosophotasia?

A

-Rare inherited disease of defective bone mineralization
-Low/absent tissue nonspecific alkaline phosphatase activity

45
Q

2 types of congenital hypophosophotasia?

A

Type 1: inherited recessive condition, detected prenatally

Type 2: inherited dominant condition, not detected until later in life

46
Q

Is type 1 or type 2 congenital hypophosophotasia lethal?

A

Type 1 (recessive)

47
Q

What is dysostosis?

A

Any condition characterized by abnormal ossification

48
Q

List 2 of the m/s sonographically visible types of dysostosis?

A

Cleidocranial:
-widening of cranial fontanelles with increase in lateral aspect of cranium

Craniofacial:
-associated with craniosynostosis + apert syndrome

49
Q

Examining the hands is best done in which trimester?

A

Late 1st or mid 2nd trimester (b/c fetus moves hands more often)

50
Q

A persistently clenched hand with an overlapping index finger is associated with?

A

Trisomy 18

51
Q

A trident hand (3 pronged look) is found in what pathology?

A

Achondroplasia

52
Q

What is polydactyly?

A

Presence of extra digits on hands or feet

53
Q

What is the m/c hand anomaly?

A

Polydactyly

54
Q

Differentiatae preaxial + postaxial polydactyly?

A

Pre: affects radial (thumb) side
Post (m/c): affects ulnar (pinky) side

(central polydactyly affects the 3 central digits)

55
Q

What is limb reduction abnormality?

A

Congenital absence or incomplete development of 1 or more limbs (or segments of limbs)

56
Q

List the terms associated with limb reduction?

A

Aplasia: absence of a bone
Hypoplasia: incomplete development of a bone
Amelia: absence of 1 or more limbs
Hemimelia: absence of 1 or more extremities below elbow or knee
Acheiria: absence of 1 or more hands
Apodia: absence of 1 or more feet
Adactyly: absence of 1 or more digits from hands or feet
Phocomelia: absence of prox part of an extremity
Meromelia: absence of part of a limb

57
Q

What does VACTERL stand for?

A

Vertebral, anorectal, cardiac, tracheoesophageal, renal, limb abnormalities

(at least 3 anomalies MUST be present to confirm this condition)

58
Q

What is club foot?

A

-Common birth defect where foot is excessively medially deviated, the bone of the foot lies in the same plane as the bone of the lower leg
-Check feet again at end of exam to ensure club foot is present

(foot should NOT be in same plane as bones)

59
Q

Club foot is commonly due to?

A

Oligohydramnios - or other things that restrict fetal movement

60
Q

What is amniotic band sequence (ABS)?

A

Group of fetal abnormalities ranging from constriction rings + edema of digits to multiple complex anomalies

61
Q

Cause of ABS?

A

Unknown

62
Q

SF of ABS?

A

Linear echogenic band attaching from 1 uterine wall to another (or from uterine wall to fetal part)

(may not be seen at all)

63
Q

What is known as the mermaid syndrome?

A

Sirenomelia

64
Q

What is sirenomelia?

A

-Rare lethal abnormality associated with maternal diabetes, MZ twinning + maternal cocaine use
-Is the fusion of both or one lower leg with renal agenesis, resulting in severe oligohydramnios

65
Q

Prognosis of sirenomelia?

A

Poor - due to renal agenesis

66
Q

Do we measure all the long bones routinely?

A

No, just femur + foot length for biometry

67
Q

When would we measure all the long bones?

A

If shortening of a long bone we must measure all of them

68
Q

List 3 steps on how to get paired long bones to image together?

A

1: Find long bone in SAG, make it parallel to floor + turn into TRV
2: Slide laterally off bone until we can no longer see it
3: Angle back to bone until it is in view again (repeat steps 2 + 3 until we have 2 bones visualized adequately)

69
Q

What does ā€œVā€ represent in VACTERL?

A

Vertebral

70
Q

How many phalanges does the thumb have?

A

2

71
Q

Kleeblattschadel (cloverleaf skull) is seen with which disease?

A

Thanatophoric dysplasia (TD)

72
Q

What form of OI is mildest?

A

Type 4

73
Q

What does micromelia result in?

A

Shortening of entire extremity