Abnormal MSK PT 1 Flashcards
What is the skeleton composed of?
- 2 tissues
- 3 cell types
What 2 tissues is the skeleton composed of?
- bone
- cartilage
what 3 cell types is the fetal skeleton composed of?
- osteoblasts
- osteoclasts
- chondrocytes
Skeletal tissue is derived from what three embryonic cell lineages?
- cranial neural crest cells
- paraxial mesoderm cells or somites
- lateral plate mesoderm
What is Cranial neural crest cells?
craniofacial skeleton
what is Paraxial mesoderm cells or somites?
axial skeleton
what is lateral plate mesoderm?
responsible for limb formation
When do limb buds begin to develop?
4th week
Development of the Fetal Limbs?
Upper limbs antecede the lower lower limbs in bud appearance, development, differentiation and establishment of final relative limb size
Order or development of fetal limbs
- Humerus and femur
- Radius, ulna, tibia and fibula
- Metacarpal and metatarsal bones
- Phalanges
skeletogenesis 4 steps?
- patterning
- organogenesis
- growth
- homeostasis
what is patterning?
final size, shape, number and arrangement of bones are determined
what is organogenesis?
bone and cartilage are formed
what is hemostasis?
The tendency of the body to seek and maintain a condition of balance or equilibrium within its internal environment, even when faced with external changes
when can we see limb buds on u/s?
7 weeks
what can we see clavicle and mandible on u/s?
9-11 weeks
when can we see hands and feet on u/s?
12-14 weeks
when can we see distal femoral epiphysis on u/s?
29-34 weeks
when can we see proximal tibial epiphysis on u/s?
35 weeks
during woutine 20 week scan what is assessed? MSK
- one femur is measures
- all 4 limbs are assessed
Femur Bilaterally Humerus Bilaterally Radius and Ulna Bilaterally Tibia and Fibula Bilaterally Hands and Feet Bilaterally Chest Diameter is assessed Ossification of skull, spine and other bones is assessed Curvature of the spine is assessed
How to measure long bone?
- Long bone length is the measurement between the distal and proximal ossification centers of the femoral diaphysis
- Exclude the proximal and distal epiphysis
Indication for careful survey of the fetal skeleton include?
- Family history with a known genetic risk
- Detection of a fetal anomaly during a routine obstetrical study
Abnormal Musculoskeleton includes?
- Pattern of limb shortening
- Degree of limb shortening
- Presence of bowing, fractures and angulations
- Hands and Feet
- Head Circumference
- Calvarium
- Facial features
- Spine
- Thoracic measurements
- Assessment of Ribs
- Serial measurements
definition of skeletal dysplasia?
- dwarfism
- umbrella term for a group of hundreds of conditions affecting bone and cartilage growth
A child born with skeletal dysplasia will present with?
- abnormal differences in the size and shape of their legs, arms, trunk, or skull.
- very short structure
- arms and legs may not be proportional with the rest of the body
classification of skeletal dysplasia?
- initially based on clinical or radiologic/pathologic descriptions
- Now classifications have evolved to include underlying molecular abnormalitie
Prenatal sonographic diagnosis of skeletal dysplasia is centered on?
combinations of abnormal finding of the limbs, rib cage, skull and spine
The most common severe skeletal dysplasias manifest with?
- severe micromelia (generalized shortening of all limbs)
- variable degrees of thoracic dysplasia
The most common types of skeletal dysplasia can be detected by what measurement?
Measurement of FL
further serial measurements are required to determine if a skeletal dysplasia is present when femur length is below?
1 to 4 mm below 2 SD point
there is high likelihood of skeletal dysplasia if femur length is?
FL is greater than 5 mm below the 2 SD point
what might be helpful in the diagnosis of skeletal dysplasia?
- fetal biometric ratios
Example:
in severe skeletal dysplasia, abdominal and head circumferences are frequently normal, while thoracic or chest circumference is decreased.
Why is Femur Length to Foot Length Ratio helpful?
Has been helpful in the diagnosis of skeletal dysplasia and in distinguishing skeletal dysplasia from severe IUGR
Why is foot length measurement helpful?
Foot length is not usually affected by the most common skeletal dysplasia and can be used to assess GA when skeletal dysplasia is suspected
Normal foot length?
nearly equal to femur length in the 2nd and 3rd trimester so that a normal femur length to foot length ratio approaches unity (1:1 ratio)
Femur Length to Foot Length Ratio with severe IUGR?
Femur length may be abnormally small, however, the femur length to foot length ratio remains essentially normal
Femur Length to Foot Length Ratio with skeletal dysplasia?
The femur length to foot length ratio decreases, since foot length is unaffected, and the femur is shortened to different degrees
what are four patterns of shortening of the long bones?
- rhizomelia
- mesomelia
- acromelia
- micromelia
Rhizomelia?
shortening of proximal segment (femur, humerus)
what is mesomelia?
shortening of middle segment (radius, ulna, tibia, and fibula)
what is acromelia?
shortening of distal segment (hands and feet)
what is micromelia?
shortening of entire limb (mild, mild/ bowed, severe)
effect of severe micromelia with skeletal dysplasia?
- lethal
- The earlier the onset, the worse the prognosis
