Abnormal Musculoskeletal System and Limb Defects

MSK system: when the optimal time to evaluate? what is most detected?

18 weeks, short limb dysplasias

whats the first indication of skeletal dysplasia?

short femur length

fetuses with femoral lengths greater than? should be investigated further to rule out limb abnormalities

2SD belowe mean for GA

what do you check when evaluating MSK?

family hx, shortening of limbs, decreased echo of fetal bones, femur morphology like bowing and fractures

what are other sono findings that suggest skeletal dysplasia?

small thorax, abnormal skull, spine, hands, and feet, polydactyly, poly, hypomineralization

what do you look for when eval the skull?

head shape, degree of skull ossification, reflectivity should be greater than the falx

how shoould you eval abnormal hands and feet?

number of digits, foot size, and shape

what the main skeletal dysplasias?

bone length anomalies, achondroplasia, achondrogenesis, thanatropic dysplasia, and osteogenesis imperfecta

name all bone length anomalies

acromelia, mesomelia, rhizomelia micromelia

acromelia

distal segment/terminal part of limb (hand/foot)

mesomelia

middle segement

rhizomelia

proximal segment (femur/humerus)

micromelia

entire limb

define Achondroplasia “Aka Dwarfism”

most common nonlethal skeletal dysplasia

achondroplasia cant be diagnosed until? many findings do not present until when?

before 24 weeks, 3rd trimester

is it compatible with life, if so, are there any complications?

yes, respiratory issues bc of small chest, neuro issues bc of compression of spine (small foramen magnum and spinal curvature, and obesity

etiology of dwarfism?

inherited- autosomal dominant, most cases- spontaneous mutation

what are the presentations of achondroplasia

rhizomelia, macrocephaly, prominent forehead, depressed nasal bridge, trident hand, small width of spine, and small thorax

achondroplasia: macrocephaly…

w/ hydrocephalus due to small foramen magnum

trident hand

hands are short and stubby w/ separation between middle and ring fingers

spine exhibits small width

lordic: arched and kyphoscoliosis: curvature

achondroplasia: small thorax causes..

abd to appear protuberant giving fetus classic bell shaped appearance

define achondrogenesis

2nd most common lethal short limbed dwarfism

etiology of achondrogenesis and can be detected as early as?

autosomal recessive and as early as 13-14 weeks

what are the sono findings of achondrogensis?

Severe short limbed dwarfism – micromelia (entire limb)

Lack of vertebral ossification, calvarium and spine
Rib fractures
Bell-shaped abdomen

define Thanatophoric Dysplasia

Most common lethal short-limbed skeletal dysplasia

what is thanatophoric dysplasia considered?

sporadic anomaly

what are the sono findings of Thanatophoric Dysplasia

same as achondrogenesis and cloverleaf skull

define Osteogenesis Imperfecta (OI) (brittle bone diease)

hypomineralization of bone and blue sclera

what are the types of brittle bone disease?

four types (i and iv not diagnosed until after birth)
type 1: patients easily fracture
type 2: lethal
type 3: may be compatible w/ life but severe deformities
type 4: bones rarely fracture (mildest)

what are the sono findings of Osteogenesis Imperfecta (OI) type ii and iii?

Multiple fractures of long bones and ribs from simple movement

Skull compressibility

Poorly ossified calvaria

limb defects (hands and feet): when evaluating hands and feet, one should asses?

presence or absence, number of digits, and posture of hand/foot

limb defect: nomenclature
define clinodactyly, mesomelia, micromelia, syndactyly, polydactyly, rhizomelia, talipes, thanatropic

look at image

define equinovarus

clubfoot, Most common anomaly affecting the feet diagnosed on ultrasound

what is this image showing?

clinodactyly, curvature of 5th finger towards 4th

what is this showing?

polydactyly

whats this showing?

syndactyly

what is this image showing?

mermaid syndrome

define sirenomelia

Congenital malformation characterized by fusion of lower limb structure

what are the sono findings and associations of sirenomelia?

Single lower limb, Bilateral renal agenesis, Single umbilical artery and maternal diabetes