Joint Development (HIP) Flashcards

1
Q

Joint Development

A
  • žBasic structure of joints formed during wks 6-7 of gestation
  • žFinal shape develops throughout early childhood under influences of the forces of movement and compression
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2
Q

Hip Joint- 12 weeks of GA

A
  • žvery deep acetabulum
  • very round femoral head
  • …femoral head very well covered
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3
Q

Hip joint- Birth

A
  • žvery shallow acetabulum
  • hemispheric femoral head
  • so…<1/2 of femoral head covered
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4
Q

Hip Joint- Birth considerations

A
  • žThis is an unstable hip but necessary for the infant to pass through birth canal
  • Risk of dislocation is greatest if in single breech position (hips flexed/knees extended)
    • b/c hamstrings could pull head of femur downward
  • After birth-risk of dislocation is with extending the hips
    • b/c iliopsoas could pull femur upward
  • Birth-10 years: forces of compression and movement contribute to an increase in depth of acetabulum
    • adult level of femoral head coverage reached by 10
    • femoral head also rounds again but never to the level of early fetal period
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5
Q

Prenatal Deformities

A
  • žFetal position is related to various deformities
    • Like hip dysplasia
  • especially true toward end of pregnancy when skeletal growth continues but space can be limited.
  • žOther space limiting factors:
    • Decreased amniotic fluid
    • Multiple births
    • Excessive force from tightly stretched uterine and abdominal walls
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6
Q

Bone Growth

A
  • žCompression or tension: loading a bone longitudinally
    • wt bearing or ms pullÜgrowth
  • Shear forces Ütorsional or twisting change

***normal pull of muscles around joint contributes to shear forces resulting in normal torsional changes in long bones

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7
Q

What about Tibia?

A
  • žAt birth-0-5°medial tibial torsionÜ 25° lateral torsion as adult
  • žAt birth—infant knee in genu varum → netrual alignment by 2yo →peak of genu valgum between 2-4yo →adulthood
    • (differs between genders and races)

***Note: if find genu varus in child aged 2-6yo ►Send for orthopedic consult!!!!

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8
Q

TORSION/Hip

A
  • žAt birth: hip is at maximal antetorsion (30-40°)
  • Rapid decrease in first year then slow until 8yo then rapid again into adoloscence to an average of 16° by 16
    • the femur “untwists” through growth, muscle action, reduction of coxa valga angle, and reduction of hip flexion contracture
    • active external hip rotation and external forces created during walking impact the changes in femoral anteversion
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9
Q

VERSION

A
  • žFemoral version = position of head of femur in acetabulum
  • Anteversion positions head anteriorly leading to hip external rotation
  • Retroversion positions head posteriorly leading to hip internal rotation
  • At birth: neonate with 40-60° of anteversion which resolves (“de-rotates) to 15-20° by 8-10 years old à 12° in adulthood
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10
Q

Who wins?

A
  • žAt birth; 30-40° of antetorsion, 40-60° of anteversion
  • Anteversion wins out and you have thighs in external rotation at typical term birth

***If you have persistent antetorsion or too much, you will see in-toeing as the hip “de-rotates”

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