wk 4 - biomechanics case study

why were horseshoes originally used for?

to protect horse’s feet against excessive wear

over the years, how has shoeing evolved?

evolved into a study of how shoeing horses may influence performance

what is corrective shoeing meant to do?

attempt to unload a specific site and/or shorten the duration that that area is bearing weight

what are the two forms of gait?

• stance phase

  • most important bc in this phase the leg bears the most weight

• propulsion phase

what is the ground reaction?

when the limb is on the ground, it’s subject to a certain amount of external impact force from the ground

what is the Ground Reaction Forces (GRF)?

• depends on how fast the horse is moving and how much they weigh

• acts in a single point in the hoor called the point of zero movement or Point of Force

what does the ground reaction mainly affect?

main effect on the leg is in the Distal Interphalangeal joint (DIP)

what does the point of zero movement not include?

• not directly below the DIP’s rotation

  • called the “moment arm“ which creates torque

what is the 2nd moment arms?

deep digital flexor tendon (DDFT) over the navicular bone

why is the DDFT the second moment arms? (1/2)

hoof lands on the ground → DDFT compresses navicular bone w a force which is proportional to the force placed on DDFT

why is the DDFT the second moment arms? (2/2)

• at breakover point, joints flex & cause there to be a reduction of GRF

  • reduces the force exerted on the joints & tendons

what is the breakover point?

point where the toe is coming off the ground & the heel is no longer weightbearing

what kind of shoes are steel shoes considered to be?

generally considered acceptable for aluminum since the steel offers more support to the hoof

what happens when shoes are applied on a horse’s hoof?

• the point of force moves closer to the center of the hoof distributing the ground forces more evenly

• decreases the magnitude of the forces near the level

what is something to note about shoes?

• have significant positive impact on the horse

  • but may occasionally have a slight negative impact

what is one issue that shoes may cause?

weight imbalance

how can shoes cause a weight imbalance?

• weight of shoes increases inertia

  • indicates the limb doesn’t resist changes to velocity of the limb as well as a barefoot horse

where is the primary change of added shoe weights present in?

in the swing phase at high speeds

how deeply can a shoe affect the navicular bone?

depending on the shoe, it may cause an increased force on the navicular bone by the DDFT by as much as 14%

besides the navicular bone, what else can the shoes affect?

• can also affect the amount of concussion sustained by the hoof

  • esp in the metacarpophalangeal joint

what does conformation refer to?

general shape, size, and static relations of the distal limbs

what does balance refer to?

both shape and function of the foot in relation to the ground & to skeletal structures of the limb both at rest & exercise

why is it a goal to achieve conformational correctness & balance?

believed that maximum efficiency is also achieved

what is the ideal hoof balance?

• a concept of what a hoof should ideally look like

  • there is much debate on this topic

  • geometric balance vs dynamic balance

what does geometric balance refer to?

the attempt to make the hoof as symmetrical as possible around its sagittal solar plane which is positioned in a prescribed position in relation to the rest of the foot

what does dynamic balance refer to?

the confirmation that allows the foot to contact the ground in a prescribed pattern

what is something important to note about the hoof?

• hoof conformation can affect biomechanics

• common belief that there is more than one structure that’s affected by even small changes

what is something to note about barefoot horses?

• have a 3 or 4 point pattern of major contact

• hoof wall & heel should always contact at a lower point than the sole does

what does the 4 point pattern include?

• heel

• lateral

• medial

• toe

what does the 3 point pattern include?

• heel

• toe

• dorsal surface

what problems can an imbalance in hoofs cause? (1/3)

• Strain of the suspensory tendon

• Strain of the DDFT

• Strain exerted on the Navicular bone

what problems can an imbalance in hoofs cause? (2/3)

• Increased uneven strain on joints

• Rubbing of joints leading to spurs

• Quarter cracks

• Inflammation of bursa of the tendons and navicular

what problems can an imbalance in hoofs cause? (3/3)

• in extreme cases fractures

• in extreme cases - founder

• Laminitis

• Stress cracks

how can hoof imbalance & lowering the heels affect the navicular bone?

can cause navicular syndrome in approx 70% of cases

if lowering heels can cause navicular syndrome then is raising heels better?

• varying results between ponies & horses

• may not always be the answer except with front feet (mostly the answer for front feet)

what is something to note about upright heels?

• promote a heel first landing

  • however, w long toes & low heels, the toes will land first