Biomechanical Properties and Behaviors of Bone Flashcards
which bone can absorb a lot of energy (shock absorbing), more flexible
cancellous bone (trabecular, spongy)
What kind of force is cortical bone strongest in?
compression
which bone fails at low deformation
cortical bone
When is cortical bone weakest
shear
Which bone can sustain large deformation
cancellous
debonding of cement lines, microfracture
tension
cracking of osteons
compression
how do muscles attenuate tensile stress?
they produce counteractive compressive stress
muscle fatigue can lead to a _____ fracture
transverse
resorption of older bone and formation of new bone
remodeling
_____ of the body’s trabecular bone is remodeled each year
25%
younger bone is more ductile or brittle
ductile
higher loading speed results in more _____ behavior
brittle
regarding bending, stresses are higher ______ from the neutral axis
further
Where will the structure break in a 3 point bend
point of application
Where does the fracture begin in a 3 point bend
on the tensile side (weaker in tension than compression)
Where will the structure break in a 4 point bend?
weakest point
an oblique fracture will occur when there is _____ compression and _____ failure
high, slow
stiffness and load to failure increase with
loading rate (30% stronger during brisk walk than slow walk
comminuted or multiple fragment fracture usually occurs in what kind of an environment
high energy
with low repetitive forces, osteoclast activity ______ osteoblast activity, leaving no time for body to repair microdamage
outpaces
Bone responds to mechanical stresses by increasing/decreasing mass according to magnitudes and directions of forces that are applied
Wolff’s law
formation of new bone without resorption
modeling
resorption of older bone and formation of new bone (osteoclasts and osteoblasts)
remodeling
what contributes to bone hypertrophy or increase of mass
osteoblast
What are the three parts of the female athlete triad?
eating disorders, amenorrhea, osteoporosis
affects 1-10% of all adolescent and college age women
mineralization peaks at what ages for women and men respectively
25-28
30-35
What does higher mineralization (larger crystals) mean for older adults?
decreased plastic deformation and energy absorption
increased brittleness
side effects of osteoporosis drugs
decreased toughness, increased microdamage accumulation
Three most common fracture sites in the aging individual
femoral neck
radius/ulna
spine
Which bone can transmit a lot of force, very strong in compression, and very stiff(does not deform much before fracturing)
cortical
cancellous bone is able to deform a lot before it fractures. this is primarily due to its
high collagen content
During isometric contractions the internal moment is ____ to the external moment
equal
During concentric contractions the internal moment is ____ than the external moment
greater
During eccentric contractions, internal moment is ____ than external moment
less
in the biomechanical muscle model, the sarcomere and passive components (endo-, peri-, and epimysium)
are parallel
The maximum torque generated by the hip abductors occurs when the muscles are in a ____ position which corresponds to the functional task of _____
lengthened, single leg stance phase of gait
An important function of the acetabular labrum is
it deepens the acetabular cup for increased stability
The right lower extremity posture that would be observed in a person who has a dramatic retroversion of the right hip? Anteversion?
duck foot, pigeon toe
The right lower extremity position that would be observed in a person who has a dramatic coxa vara of the right hip would be
right genu valgum (knock kneed)
a newborn has increased
coxa valga (150 degrees)
T or F During 2-legged stance, the hip muscles are primarily responsible for stability of the coxafemoral joint
F - NO muscle activity is required to maintain upright, neutral posture at the hip, ligaments and joint capsule provide stability
3 primary functions of the hip
1 support HAT
2 static erect postures
3 dynamic postures
What is the loose (open) pack position of the hip
35 degrees flexion/abduction, slight external rotation
What is the closed packed position of the hip
maximum extension/int rot/abduction
What are the two articulating surfaces of the hip
acetabulum of Os Coxae and head of Femur
Which ligament of the hip is known as the Y
iliofemoral (anterior)
the others are pubofemoral (ant/inf)
ischiofemoral (post)
a ring of fibrocartilage that encircles the acetabulum and its functions include shock absorption and pressure distribution; joint lubrication; enhances joint stability
acetabular labrum
which portions of the acetabular labrum is most innervated
anterior and superior
what finishes the acetabular labrum
transverse acetabular ligament
What structure deepens the acetabulum by 20 or more percent
acetabular labrum
Where is the articular cartilage thickest for femoral head and acetabulum
superiorly
What is the only part of the femoral head that is not covered in articular cartilage?
fovea (attachment of the ligamentum teres)
What happens if there is a disruptions of the ligamentum teres?
avascular necrosis
Angle of inclination in
Infants
adults
elderly
150
125
120
females can have a greater pelvic width, which will do what to their angle of inclination?
lessen it
when angle is greater than 125, it is called
when it is less than 125, it is called
coxa valga
coxa vara
coxa valga corresponds with genu….
coxa vara corresponds with genu….
vara - bowleg
valga - knock-kneed
The typical angle of torsion for adults is _____ degrees
12
Anteversion causes _____ rotation of the femur when the angle of torsion is ______
internal
greater than 12 degrees
Retroversion causes _____ rotation of the femur when the angle of torsion is
external, less than 12 degrees
forces in the hip are transmitted to the femoral shaft through the femoral neck. this is what kind of system
cantilever
accordion-like folds are found on the inferior and superior aspects of the joint capsule. these are called
frenula (synovial folds)
What do the frenula permit
full abduction and adduction range of motion
Why do humans have extremely limited hip hyperextension
the three dense and strong ligaments wrap around the hip joint capsule in a clockwise direction
T or F The ligamentum teres supports the hip joint
F, its primary purpose is to serve as a guid for oburator artery branch traveling to fovea on head of femur
What are the primary muscles involved in unilateral stance
hip abductors, opposite lumbar erector spinae
What happens to the right femur if you can see Trendelenburg Sign in right unilateral stance?
pelvis?
lumbar spine?
adducts
left lateral tilt
right lateral flexion
