Form & function of the equine foot as it pertains to farriery Stephen E. O Grady, DVM, MRCVS Virginia Therapeutic Farriery In Assoc. with: Palm Beach Equine Clinic Keswick, Virginia 22947, USA Email: sogrady@look.net Website: http://www.equipodiatry.com If one knows foot anatomy, function and biomechanics All the farriery answers are there! 1
Farriery is the only aspect of equine veterinary practice that requires input from two professions. The veterinarian and the farrier Share the Flame! 2
The horse s foot is unique as it is a biological entity that follows the laws of physics. (S. O Grady, 2009) A Mechanical Marvel Drawing by Dr. Chris Pollitt A Mechanical Marvel Static Dynamic PROPORTIONALITY 3
FORM The structure of the parts & the way they are arranged Dr. Andy Parks (Glass Horse) The Foundation The Distal Phalanx Unique 3 Surfaces 3 Borders 4
Stratum periostale Ginglymus or hinge joint L M Saddle joint 5
6
Ungual Cartilages Play a role in: Lateral expansion of hoof capsule Equalizing pressure within the hoof Decreasing concussion 7
Digital Cushion Composed of fibrous trabeculae, elastic fibers and fat cells Not all feet are Created Equal! 8
Hoof Capsule Wall Sole Frog Bulbs Hoof is the integument of the foot Perioplic Coronary Corium's Solar Lamellar Cuneate 9
Hoof Wall 1 2 3 1. Stratum externum 2. Stratum medium 3. Stratum internum Properties of the hoof wall Hoof Capsule is More Fracture Resistant Than Bone 10
Bars At the heels the wall is inflected at an acute angle; runs forward and inwards Weight bearing (represents wall under foot) Additional strength to heel Allows lateral movement The bars should bear weight, not the digital cushion Responsible for the dynamic properties of the palmar foot 11
Frog Elastic horn More moisture that any other part of the foot (aided by sweat glands in the digital cushion above) Assists the digital cushion with expansion of the foot Plays a role in concussion Aids in traction Adaptations Hoof Wall adapted to weight bearing Sole adapted for protection and weight distribution Frog and digital cushion adapted to allow expansion at the heels and dampen vibrations 12
BLOOD SUPPLY 3 1 2 THE VEINS OF THE HOOF COLLECT INTO A COMPLEX OF INTERCONNECTING VESSELS (plexuses) 13
FUNCTION The way the structures fulfill their purpose FOOT 1. PROTECTION 2. ACCEPT WEIGHT 3. ABSORB CONCUSSION Protection Biomechanics of Weight Bearing and Movement Why does it matter? Because abnormal stresses within the foot predispose the foot to injury Because the veterinarian and farrier can work to mitigate those stresses to prevent disease or to treat disease after it has occurred 14
Suspension of the Distal Phalanx within the Hoof Load Bearing Load Sharing 15
Think Mechanics! Forces Weight bearing: interaction between the ground and the foot Forces The ground reaction force (GRF) Represented as a vector Center of pressure (COP) 16
Moments about the Distal Interphalangeal Joint at Rest Extending Force Flexing Force 17
How can we influence these biomechanics to benefit the horse Cannot significantly change force of weight bearing. Can change Center of Pressure Can change Distribution of Pressure Can change Length of Moment Arm Can reduce impact vibrations 18
Move the center of pressure Dorsal to palmar Move the center of pressure Lateral to medial or vs. Alter the distribution of forces 19
Change ease of movement 20
Functions of the heel Dissipate energy during the impact phase of the stride Facilitate the expansion of the hoof Absorb energy of concussion during the stance phase Share the load How does the foot expand? Traditional Ideas Frog Pressure Middle Phalanx Descent The frog loads with weight bearing and this causes the pressure in the digital cushion to increase and push the walls out The middle phalanx descends into the space between the collateral cartilages which increases the pressure in the digital cushion Traditional ideas appear to be wrong: Digital cushion pressure decreases during weight bearing! Other? Thus it appears that the structure of the hoof and its attachments to the distal phalanx cause the walls to move apart this causes digital cushion pressure to drop 21
Discussion Thank You! Jendaya Regina O Grady 22