Ch 13 Skeleton Flashcards
Fetal limb buds are seen as early as how many weeks by EV?
8 weeks (lower buds seen before upper buds)
Long bones fully develop during what weeks?
During 7-12 weeks
Bones in hands + feet are developed b/w what weeks?
11-13 weeks
The long bones of the femur, humerus, rad/uln + tib/fib can be accurately measured from what week onward?
12 weeks on
Which femur should we measure?
The most anterior one
(posterior femur looks artifactually bowed + shortens our length inaccurately)
The femur grows how many mm per week?
14-27 weeks: 3mm per week
3rd trimester: 1mm per week
Femur length varies depending on what maternal factors?
Maternal height, weight + ethnicity
Is the tibia or fibula thicker?
Tibia
Location of tib/fib?
Tib: medial
Fib: lateral
Is the radius or ulna longer?
Ulna
Location of rad/uln?
Rad: thumb side (lateral)
Uln: pinky side (medial)
How many independent digits do the hands have?
5 - they vary lengths
How many phalanges does each hand digit have?
3
(thumb only has 2)
Is a constantly fixed hand position abnormal?
Yes - should always be seen in flexion + extension
How many tarsal bones + digits are there in the foot?
5
How many phalanges does each foot digit have?
2
Why can the foot measurement be used to determine gest age?
B/c it has a characteristic pattern of normal growth
What is skeletal dysplasia?
-Abnormal development of cartilaginous + osseous tissues
-Results in bones that appear short, thin, deformed or that fail to forma at all
Is diagnosing skeletal dysplasia hard?
Yes - should document + image each limb at the start of the exam when scanning an at-risk fetus
How do the long bones appear with skeletal dysplasia?
-May be shorter
-Must evaluate for bowing + fractures
What are the 4 categories of short-limbed dysplasias?
Rhizomelia: prox part is shortened
Mesomelia: middle part is shortened
Acromelia: distal part is shortened
Micromelia: entire extremity is shortened
What other abnormalities should be noted when assessing for skeletal dysplasia?
-Abnormal # of digits + fluid volumes
-Facial or cardiac defects
-Skull shape (cloverleaf deformity)
Lethal skeletal dysplasias are often accompanied by what?
Pulmonary hypoplasia
What is the m/c form of lethal skeletal dysplasia?
Thanatophoric dysplasia (TD)
(thanatophoric = death bearing in greek)
Is TD m/c in males or females?
Males
2 types of TD?
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)
What is the āchampagne cork appearanceā associated with?
TD - is a narrow thorax with a protruding abdomen
How is the prognosis for TD?
Poor - m/c stillborn or die after birth due to pulmonary hypoplasia
What is the m/c nonlethal type of dwarfism?
Achondroplasia
(occurs equally in M/F)