Biomechanics Development Flashcards
how is the newborn skeleton different from the adult skeleton
made of cartilage
-more compliant
-weaker and capable of creep
bone greadually copies configuration of cartilage over the first 25 years of life
shear forces
- orientation to epiphyseal plate
- caused by…
- results in…
parallel to epiphyseal plate
normal pull of muscle around a joint
results in normal torsional changes in long bones
ex. lateral tibial torsion
compression forces
-orientation to epiphyseal pate
perpendicular to plate
what determines the size, shape and mass of your bones
genetics
environment
mechanical forces applied to bone through movement
pathology
skeletal development timeframe
5th week of gestation to end of skeletal ossification (25 years)
neonatal biomechanical problem list
rigid kyphotic spine hip soft tissue contractures shallow acetabulum femoral structure genicular differences tib-fib torsion ankle and foot structure
resolution of rigid kyphotic spine
- when and how does it begin?
- when can a child perform a cobra
- what is required to successfully perform a cobra?
begins in 1st month of life as baby learns how to lift head against gravity in prone
capable of cobra by 4th or 5th month
requirements
-controlled extension throughout cervical, thoracic, and lumbar spine
-stabilize pelvis via simultaneous contraction of gluteal muscles
development of full mature spinal curves take ____
years of movement against gravity in a quadruped, sitting and standing position
hip soft tissue contractures
-which structures contribute to tightness
hip flexion
-iliofemoral and ischiofemoral (anterior) ligaments
-hip flexors (iliopsoas, sartorius, rectus femoris)
lateral rotation contracture
hip flexion contracture impeded what arthrokinematic movement?
distal and anterior glide of femoral head
shallow acetabulum
-how does acetabular shelf form?
muscle tension and body weight
-act to pull the femoral head into the acetabuluim
activities that apply hip extension, medial rotation, and abduction force (newborn kicking, 4 point, crawling, standing)
differences in the femur between a newborn and adult
coxa valga
antetorsion
femoral varus bowing
angle of inclination in newborn
150 degrees (adult 125)
how is the issue of coxa valga resolved
enlarge of greater trochanter
-due to action of piriformis, gluteus medius, and gluteus minimus
-i.e., external rotators, abductors, and extensors
this compression leads to a laying down of bone tissue along the uppermost border of the femoral neck
femoral varus bowing
-how does it resolve?
resolves by cantilever flexure drift
-compression forces cause resorption of bone on convex side and new bone growth on concave side
femoral antetorsion
- what is it?
- angle in newborns
- angle in adults
medial twist of the femoral shaft, distal on proximal
newborn - 40 degrees
adult - 10 degrees
how does antetorsion resolve in children
resolution of hip flexion contracture
-allows glut. max. and add. magnus to fire
consistent tensile loading by the muscles that extend and laterally rotate the hip
what muscle stabilizes the pelvis/femur during actions that extend and laterally rotate the hip
-this muscle with contribute to resolution of…
gluteus medius
-will contribute to resolution of antetorsion and coxa valga
why does the newborn appear laterally rotated if they have femoral antetorsion
soft tissue contracture (lateral rotators)
retroverted acetabulum
appropriate femoral torsion values at
- birth
- 1 year
- 9 years
- adult
birth: 40
1 year: 35
9 years: 21
adult: 15-20
differences in knee between newborn and adult
flexion contracture
medial genicular position
genu varum
how great is the knee flexion contracture in newborns?
-when does it resolve?
30 degrees
resolves in first few months of life
medial genicular position
- newborn appears to have…
- when does it resolve
- resolves with what type of activities
apparent tibial varum resolves with knee flexion contracture activities -belly crawling -walking -these activites apply lateral rotation force to proximal tib-fib
changes in genu valgum/varum from birth to adulthood
-what causes the changes
genu varum early in development
-stimulates bone growth on medial condyles
genu valgus at 2-3 years
-stimulates bone growth on lateral condyles
genu valgum resolves through weight bearing
how much genu valgum/varus is present at…
- birth
- 3 years
birth
-17 degrees varum
3 years
-12 degrees valgum
genu valgum to ideal alignment
- how much valgum is present at 8 years
- how does it resolve
8 years: 5 degrees resolution: compression forces on condyles due to -decrease in coxa valga -genicular position -femoral varus bowing
lower leg torsion at the transmalleolar axis (TMA)
- torsion in newborn
- torsion in adult
newborn: 0 degrees
adult: 20 to 30 degrees posterior to frontal plane (fibula behind tibia)
how does TMA torsion occur to resolve to adult values?
-what type of movements cause this?
requires lateral rotatory torque across growth plates of tibia and fibula
movements
-toe standing
-ambulation
“W” position may lead to increased…
femoral anteversion
sitting on the feet is commonly associated with…
internal tibial torsion
differences in ankle between newborns and adults
excessive talocrural dorsiflexion
shortened fibula
differences in ankle between newbors and adults
hindfoot varus - open chain
hindfoot valgus during infancy and the onset of weight bearing
relaxed calcaneal stance angle
-equation
RCS = 7 minus (age of child)
-Valmassey
this is the amount of calcaneal valgus they should have
foot progression angle
- how is it measured?
- negative versus positive value
- what should values be at birth, 3 years, and adult
angle between -longitudinal axis of foot -line of progression of gait in-toeing = negative value out-toeing = positive value birth: 10 degrees 3 years: 2-6 degrees adult = 0- degrees
thigh-foot angle
-how is it measured
prone
knee at 90 degrees
foot in congruity
measure posterior thigh bisection and plantar heel bisection
-so you draw a line through the middle of the thigh and a line through middle of the heel to the 2nd toe, and you compare the angle they make
typical thigh-foot angle at
- 1 year
- 3 years
- 5 years
- 15-19 years
- adult
1 year: -3 degrees (toes point medially) 3 years: +5 degrees 5 years: +11 degrees 15-19 years: +12 degrees adult: +18 degrees
antetorsion vs anteversion
antetorsion
-relation of femoral head to femoral condyles
anteversion
-relation of femoral head to frontal plane
