Exam 2 Biomechanics

purpose of spinal column

1) protect the spinal cord, nerve roots, and body organs

2) allow for upright posture and maintain balance

3) provide motion

anatomy of the cervical spine

seven vertebrae - lordosis

- C1 = atlas

- C2 = axis

anatomy of the thoracic spine

twelve vertebrae - kyphosis

- ribs (10 attached, 2 floating)

- vertebral bodies are wedge shaped

anatomy of the lumbar spine

five vertebrae - lordosis

- best at flexion/extension

anatomy of the sacrum

five vertebrae

- coccyx right below

which mammal doesn't have seven cervical vertebra?

manatees

vertebral body

anterior of spinal cord, shock absorbing (compressive force)

vertebral arch

posterior of spinal cord, articulating

transverse process

lateral projections on both sides of the vertebral arch

spinous process

posterior projection of a vertebra

pedicle

body --> transverse process

laminae

transverse process --> spinous process

vertebral foramen

spinal cord runs here

atlas and axis articulation

half of the rotation of the cervical spine occurs here

function of the cervical spine

1) support the axial load of the head

2) keep the head upright

3) allow mobility of the head

which cervical vertebrae is most prominent?

C7

osteoarthritis of the spine

loss of disc height affects the alignment of the facet joints

- causes bone spurs/the development of arthritis

stenosis

narrowing of vertebral canal

- symptoms are worse because impingement is of spinal cord, not a "pinched" nerve root

unilateral

outside spine

bilateral

inside spine

what movement is limited by the ribs?

lateral bending

scoliosis (adolescent idiopathic scoliosis)

frontal plane S or C curve in the thoracic/lumbar spine

- paired with transverse plane rotation of the vertebrae causing the ribs to rotate as well

- >18°

- measured using Cobb angle (magnitude)

what two things affect the severity of scoliosis?

1) age of patient

2) double curves

compression factures of the spine

compressive load fractures the anterior aspect of the vertebral body

- bone is good in compression, but not as good when it is unevenly distributed

- common in people with osteoporosis

intervertebral discs

"jelly filled doughnut"

made up of annulus fibrosus and nucleus pulposis

- treatment = spine extension

annulus fibrosus

layers of fibrocartilage that are angled (cross hatched)

- only the outer edge has blood supply

nucleus pulposis

squishes throughout the day due to compression

- toothpaste consistency

- mostly water

- decreases with age

"slipped disc"

nucleus pulposis bulges posteriorly

- occurs due to forward flexion (bending forward, coughing)

why is the spine curved?

- shock absorption

- balance

- flexibility

- evenly distributed body weight

kyphosis

concave towards anterior

- hunching

lordosis

concave towards posterior

- arching

normal cervical lordosis

30-40°

normal thoracic kyphosis

20-40°

normal lumbar lordosis

20-45°

cause of excessive lumbar lordosis

usually due to weak abdominal muscles or tight hip flexors

Thomas test

assesses tight hip flexors

- hip should be parallel to the floor

- if hip is flexed and knee is straight, the hip/quadriceps are tight

- if hip is abducted, IT band tight

steps to using a goniometer

1) align the center of the goniometer with the center of the joint

2) hold the stationary arm along the non moving joint segment (usually proximal)

3) move the joint through it's range of motion, and align the moving arm with the moving segment (usually distal)

four functions of the foot/ankle

1) weight bearing

2) adapt to ground reaction force

3) accommodate terrain

4) provide balance

three points of contact of the foot

1) first metatarsal head

2) fifth metatarsal head

3) heel

- creates stability

- most people naturally bear weight more through medial or lateral border

rearfoot

talus and calcaneus

midfoot

navicular, cuboid, and cuneiforms

forefoot

metatarsals and phalanges

three arches of the foot

1) medial longitudinal arch

2) lateral longitudinal arch

3) anterior transverse arch

medial longitudinal arch

an arch of the foot running from the heel to the base of the big toe on the inside of the foot

- high arch = rigid

- flat arch = flexible

best to be in between

lateral longitudinal arch

an arch of the foot running from the heel to the base of the pinky toe on the outside of the foot

- more prominent in people with high arches

anterior transverse arch (metatarsal arch)

the short lateral arch of the foot formed by the heads of the metatarsal bones

- collapse = pressure on metatarsal heads

ankle mortice (talocrural joint or tibio-talar joint)

primary responsibility is dorsiflexion and plantarflexion

- sagittal plane

subtalar joint

motion of the calcaneus underneath the talus producing inversion and eversion (frontal plane motions)

- joint axis at 45 degrees in the frontal and transverse planes

- in closed chain, calcaneus is locked to the ground and motion primarily occurs as the talus rolls over the calcaneus

- talus is also "rolling" through dorsiflexion and plantarflexion

pronation of the ankle

combined motion of eversion, abduction, and dorsiflexion

supination of the ankle

combined motion of inversion, adduction, and plantarflexion

pronation in weight bearing

relatively unstable, but making contact with the entire foot allows the foot to contour to what you're walking on

supination in weight bearing

more stable, but rigidity means it cannot adapt to the terrain as well

transverse tarsal joint

made up of calcaneal-cuboid joint and talonavicular joint

- allows the forefoot to rotate on the rear foot

- keeps the tarsals on the ground in weight bearing as twisting occurs at the subtalar joint

- inversion locks the transverse tarsal joints for push off

- eversion unlocks the tarsal joint so the foot can accommodate to the ground

great toe (hallucis)

most important toe for maintaining balance

- provides a lever for push off at the end of a step or during jumping/ running motions

hallux valgus

transverse plane deformity where the proximal phalanx migrates laterally with respect to metatarsal

- often happens in pronators

- flexor hallucis becomes an adductor

hallux rigidis

limited hyperextension of MTP joint

- can't "roll over" the big toe

- impacts normal walking and running

- increased pressure, risk for callusing/skin break down

- can lead to pain and disability

plantar aponeurosis

thick, deep layer of the plantar fascia that attaches on the plantar surface of the calcaneus

- has some extensions proximal to connective tissue surrounding Achilles' tendon

- is stretched during dorsiflexion of the ankle and hyperextension of the toes

- has incredible tensile strength

plantar fasciitis

typically pain at the arch closest to the heel (insertion)

- more common with tight Achilles and high arches

pes cavus

increased medial longitudinal arch

calcaneal varus

calcaneus moves into varus position during weight bearing (usually rigid)

cavovarus deformity

pes cavus and calcaneal varus ("supination")

- more likely to report ankle pain

pes planus

a flattened or elongated medial longitudinal arch

calcaneal valgus

calcaneus moves into valgus position during weight bearing (usually flexible)

planovalgus deformity

pes planus and calcaneal valgus ("pronator")

- more likely to report knee pain

Feiss' line

a line running from the medial malleolus to the first metatarsal head

- marking where navicular falls compared to sitting or standing (navicular drop)

center of mass

single point of a body about which every particle of its mass is equally distributed

- the point at which the force of gravity may be considered to act

- approximately 1/2" anterior to S2

line of gravity

action line of the force of gravity, vertically acting on the center of mass

base of support

the area formed under the body by connecting with one continuous line all points in contact with the ground

balance

maintaining the line of gravity within the base of support

ground reaction force (GRF)

the forces that act on the body as the result of its interaction within the ground

- equal and opposite in direction and magnitude to the force the body applies to the ground

ground reaction force vector

the vector representing ground reaction force

- where it passes in relation to the body indications what "moment" will occur at that joint

what must happen for a weight bearing joint to be stable or in equilibrium?

the ground reaction force must fall exactly through the AXIS OF ROTATION, or else there must be a muscular force to counteract the moment caused by gravity

posture

the relative arrangement of body segments

- the alignment of body parts whether upright, sitting, or recumbent

- assessment of body position and the long-term repetitive and static forces acting on the body

- middle 50% of available range is the safest

vertebral load

distance from center of rotation of segment to the load

- weight of segment + weight lifted

- body positioning

correct posture

position that minimizes stress to each joint

- mechanical stress

- minimal muscle activity needed to maintain

- within mid-range of motion

best performance

- efficiency of respiration

- decreased pain

faulty posture

position that increases stress to joints

- extremes of motion

causes cumulative stresses that may result in pathology

- articulate cartilage wear, osteophytes

- soft tissue weakened, stretched, or tightened

what causes faulty posture?

1) anatomy, disease, or pathology

- osteoarthritis

2) positional

- habit

- social

- muscle imbalance or tightness

3) structural

- spinal fusion

posture observation

must observe all joints, in all three planes of motion (sagittal, frontal, transverse) and from all four sides (anterior, posterior, lateral)

anterior to ankle muscular response to line of gravity

stability provided by plantar flexors to counteract anterior rotation of tibia

anterior to knee muscular response to line of gravity

stability provided by the ACL, posterior capsule, with tension in the hamstrings and gastroc to prevent hyperextension

posterior to hip muscular response to line of gravity

posterior rotation controlled by hip flexors to prevent hyperextension

trunk muscular response to line of gravity

minimal muscle activity is required when line goes through center of lumbar and cervical vertebrae

ideal posture of the head

neutral, not tilted forward or backward

ideal posture of the C-spine

normal lordosis

ideal posture of the scapulae

flat against the upper back

ideal posture of the shoulders

not elevated or depressed (spine of scapula in line with T3)

ideal posture of the T-spine

normal kyphosis

ideal posture of the L-spine

normal lordosis

ideal posture of the pelvis

neutral (slight anterior pelvic tilt, not rotated to one side, not higher on one side)

ideal posture of the hip joints

neutral, no flexion or hyperextension, not abducted or adducted

ideal posture of the knee joints

neutral, no flexion or hyperextension, no genu valgum or varum

ideal posture of the ankle joints

neutral, tibia is vertical, no calcaneal valgum or varum

ideal posture of the toes

toe out - approximately 5-7° of external rotation

three common types of poor posture

1) kyphosis lordosis posture

2) flat back posture

3) sway back posture

- common in basketball players (tall people)

short/stiff muscles of kyphosis lordosis posture

- lumbar erector spinae (trunk extensors)

- hip flexors

- pectoralis major

- levator scapula

long/weak muscles of kyphosis lordosis posture

- abdominals

- lower cervical and upper thoracic erector spinae

- rhomboids

short/stiff muscles of flat back posture

- rectus abdominus

- hamstrings

- thoracic erector spinae

long/weak muscles of flat back posture

- lumbar extensors

- possibly hip flexors

short/stiff muscles of sway back posture

- upper abdominals

- hip extensors

- hamstrings

long/weak muscles of sway back posture

- lower abdominals

- lower thoracic extensors

- hip flexors