equine anatomy exam 2

Kinematics

Movement through space; ex: joint angles, etc.

Kinetics

Measurement of force; measure of how much weight animal carries on each limb

Cinematography

most widely used, uses video to analyze gait; not continuous and skin displacement of markers can skew data

Electogoniometry

measures changes in joint angles continuously using sensors; horse is large and difficult to find center of rotation

Dynamography

Measure forces and pressure (kinect analysis); particularly useful in lameness studies

force plates

used for dynamography; difficult to get spread of accurate data

instrumental shoes

force plate inside a shoe; gets data over multiple strides but adds weight and alters movement

Gait

Way of going, predictable; characterized by distinct rhythm or movement of the feet, legs, and beat

Stride

Any single movement forward, completed when legs return to their original positions

Step

distance between two sequential hoof prints or legs in a movement

Stance time

amount of time limb is bearing weight; indirectly shows force

Swing time

amount of time limb travels through air

Differences in humans and horses: gait analysis

Horses have very predictable gaits and neural movements use the extra-pyramidal circuit (spinal cord); mass all-in-one control

Humans use the pyramidal circuit and have delicate movement control. Only horse’s head and neck movements are pyramidal

Walk

4 beat gait, no suspension; L and R side move together independently (RH, RF, LH, LF)

Trot

2 neat diagonal gait w/ suspension; all four feet are off the ground between beats

Canter/lope

asymmetrical 3 beat gait w/ suspension; lead determined by last foot to fall and horse is off ground between series of 3 beats

gallop/run

4 beat gait w/ a moment of suspension; extension of canter

Back/reinback

2 beat diagonal gait; legs are moved backward fairly slowly

How is speed related to stride frequency and stride length?

Speed = SF + SL, speed causes SL to increase linearly but SF to increase non-linearly; EX: harder tracks increase SF but decrease SL

Treadmills

Horses adapt rapidly at trot, but at the walk adaptation occurs much slower; shows increase in SL at the same speed as track

what variables do you need to control for w/ biomechanical gait analysis

trot at same speed (velocity); do not touch head, its a part of the gait; point of stride

Hunters

very little knee (carpal) movement w/ larger angles, long stride, scapula rotation

Bascule

roundness of the horse’s jump; horse should lower head and reach with its head/neck

horse leg position over jump

horse’s forearm ideally forms parallel line to the ground, knee down should be tucked in close to body

jumpers

long, ground covering stride; uphill w/ ability to transfer weight onto hindquarters

dressage

ability to transfer weight onto hindquarters; fetlock, hock, stifle joint flexion

western pleasure

long ground covering stride; string hindquarter w/ ability to transfer weight to hind end; minimal carpal movement; scapula rotation

reining

ability to transfer weight to hind end, good extension of front legs

gait quality

ability for horse to move balanced, in a manner suited for purpose/discipline; aesthetically appealing

stide length (extension/reach)

distance between the ground strike points of the same hoof

stride action

arc shape and height; more weight on hind end = higher arc

stride rhythm and cadence

pattern of movement and beats of the legs/hooves

stride speed (pace)

forward time/distance

purity of gait

presence or lack of rhythm/cadence and/or regular footfall pattern of gait

trueness/way of going

straight breakover and forward swing of each leg/hoof

impulsion

forward force or power, especially from hind

how to measure swing time

temporal; 1st frame entire foot OFF ground to 1st frame foot ON ground

how to measure stance time

temporal; 1st frame entire foot ON ground to 1st frame foot OFF

suspension time

temporal; how long horse is fully suspended

breakover time

temporal, end of stance phase; from heel off to toe off

stride velocity

speed of horse

angular velocity

how quickly horse closes joint angle

protraction

angle/distance of leg in front

retraction

angle/distance of leg behind

angle extraction

measure through frame

why is swing phase usually most focused on?

expressiveness/extravagance of movement most apparent especially late in swing phase (leg most extended away from body, max of protraction and start of retraction)

why is stance phase important?

large forces are applied to musculoskeletal system and injury is most likely to occur

what is a good quality mover?

longer stride duration, lower stride frequency; more retraction of F and protraction of H (allows for increased propulsion); short stance and long swing duration

what gait qualities lead to a long stride?

slow stride frequency, long swing phase, large degree of scapula rotation, maximal hindlimb protraction

what gait qualities lead to more suspension?

maximal fetlock extension along with maximal stifle + tarsal flexion in the stance phase

advanced diagonal placement

time between hindlimb contact and forelimb contact w/ ground in trot; diagonal hindlimb will touch ground 1st and ideally be as far as possible under the body

treadmill training

stride duration and stride length increased; stance phase reduced

horses in dressage/jump training

protraction + retraction range of the forelimbs decreased (increased collection), stance duration decreased (swing duration increased), max protraction of hindlimb occurred earlier in stride (hindlegs underneath body faster)

training effects

forehand = more elevated than hind (flexion of hindlimb joints and elevation of withers + shoulders), hindlimbs increase ground reaction force

maturing horse study findings

metacarpal and metatarsal segments did not increase significantly; radius and tibia grew proportionally to height increase; larger height increase in forelimb than hind limb

elbow, carpal, fetlock joint angle flexions were the most significant differences; joint angle patterns were similar

where does differences in swing phase generate from?

differences in stance phase

lameness

an alteration of normal gait due to functional or structural disorder in the locomotor system

causes of lameness

pain, mechanical, neurogenic/muscular/vascular

supporting limb lameness

putting weight on limb hurts, usually in hoof/distal limb

swinging limb lameness

swinging in air hurts, usually more upper leg

what kind of lameness is most common?

mixed or supporting

bilateral lameness

both sides (ex: RF + LF) are lame

grade 1 lameness

difficult to observe and is NOT consistently apparent

grade 2 lameness

difficult to observe at a walk or trot in a straight line, but is consistent in certain circumstances (ex: turning)

grade 3 lameness

lameness is observable at a trot under ALL conditions

grade 4 lameness

lameness obvious at a walk

grade 5 lamness

lameness produces minimal weight bearing or complete inability to move

comparisons in a lameness exam

1) individual to “normal” population

2) individual to its own motion pattern (ex: nerve blocks)

3) left side compared to right

why watch trot for lameness exam?

trot is even 2 beat gait, so changes are more apparent. More impact on limb than walk

which injuries show on soft surfaces?

soft tissue, stretches soft tissue more

categories of locomotor changes

temporal stride pattern, hoof trajectory (flight arc), limb movements and joint angle patterns,

temporal stride pattern in lame horses

relationship between lameness and the timing of limb placements

how do lame horses slow velocity?

increasing stride duration, reducing stride length, increasing stance duration; occurs with both legs equally

suspension phase in lame horses

decreased, usually asymmetrical; suspension phase after stance phase of the lame leg is shorter due to decreased propulsion

advanced diagonal limb placement in lame horses

front leg touches ground slightly first, even in front leg lameness; this is due to increased load in front end

hoof trajectory (flight arc) in lame horses

lower max height of the hoof during protraction; supporting limb lameness: less impact/propulsion swinging limb lameness: potential difficulty in flexing joints

protraction + retraction of limbs at the walk in lame horses

forelimb lameness: reduced retraction of front limb; hindlimb lameness: reduced protraction of hindlimb

how does the hoof land?

heel first

distal joint angle patterns in lame horses

decreased flexion/extension of joints in lame leg during stance phase results in less vertical ground forces on lame leg, increases vertical ground forces on the sound leg

lame leg = bigger angle, less weight

sound leg = smaller angle, more weight

proximal joint angle patterns in lame horses

proximal joints flex slightly more on the lame leg when loading due to muscular control in an effort to load limb more gradually

lame leg = smaller angle

sound leg = larger angle

head movement in sound horse

head works as a pendulum; head reaches its lowest point at midstance then rises to highest point after the end of stance phase/during swing phase; symmetrical so occurs twice during a full stride

head movement in lame horse

head lowering during stance phase of lame leg is decreased, changes proportional to degree of lameness

head down = sound leg

head up = lame leg

hind limb lameness (os sacrum)

os sacrum shows same pattern as head, shows left less lifting and lowering during stance phase of lame leg

hind limb lameness (tuber coxae)

tuber coxae moves more on the lame limb as horse avoids impact from landing

joint angles in mixed/swinging lameness

reduction in joint angles during the swing phase; not seen in supporting leg lameness

bilateral lameness

tricky to diagnose due to lack of typical asymmetrical patterns; locomotion is usually “stiff”, “short”

hoof wall

exterior of the hoof, attaches to coffin bone through the laminae

what the hoof wall is made up of

hoof horn, a skin derivative

insensitive laminae

where laminae attaches to hoof wall, hard and insensitive

sensitive laminae

where laminae attaches to coffin bone, much softer

where is the horn produced

corresponding area of dermis (corium)

horn regeneration time

8-10 mm/month

time is takes hoof to fully grow out/replace itself at the toe?

12 months

time is takes hoof to fully grow out/replace itself at the quarters?

6-8 months

time is takes hoof to fully grow out/replace itself at the heel?

4-5 months

white line

indicates junction between sensitive and insensitive laminae; typically tight and nonporous

digital cushion

beneath the frog, fibrous mass of tissue that provides shock absorption for foot and pumps blood back up

what is the main function of horse shoes throughout history?

protection

fullering of shoe

allows nails to be recessed (flush w/ shoe, less torque on nail), fills with dirt to improve traction

front vs hind feet

front hooves are wider (heel takes more weight) and have a smaller (more acute) angle of ideally 45. hind foot is narrower (toe takes more weight), toes out slightly and has a wider angle of ideally 55 degrees