Lecture 1: Equine musculoskeletal anatomy and conformation

- the shape or structure of something, like various body regions relative to each other or in general appearance

- structure is not easily changed

What is conformation?

- size

- shape

- height

- angles

- contours

- transitions

- relative proportions

- left-right symmetry

- muscle development

- breed standards

What are conformational features?

- affects function

- affects performance

- can lead to injury

Why is confirmation clinically important?

- a broad base of support

- equal weight bearing across all limbs

What does ideal conformation provide?

- false --> function affects form by changes in structures, which can lead to lameness

True or false

- conformation affects form

- left-right hood asymmetry

- heel height asymmetries

- hoof landing

- medial-lateral hoof wall imbalance

What are examples of changes in function that lead to changes in form that can lead to leamness?

- the position in which someone holds their body when standing or sitting

- a function that can be modified or trained

What is posture?

- often due to pain, weakness, or neurologic deficits

Why might posture be altered?

- laminitic stance

- unweighted limb (normal resting or lameness)

- ataxia base wide stance

- severe weakness

What are 4 examples of altered posture?

- laminitic stance

- shifting weight off front feet

What is this altered posture and why?

- leaning due to severe weakness

What is this altered posture and why?

- base-wide, toe in

- fetlock osteoarthritis or splint bone disease

What is this conformational fault and what can it lead to?

- base-wide, toe out

- fetlock osteoarthritis or splint bone disease

What is this conformational fault and what can it lead to?

- base-narrow, toe out and base narrow, toe in

- fetlock osteoarthritis or splint bone disease

What are these conformational faults and what can it lead to?

- base wide stance

- pain or ataxia

What is this postural fault and what can it be cause from?

- base-wide, toed out

- splint bone dz due to extra strain on interosseous ligament and strain on fetlock joint

What is this stance and a common DDx for it?

- entire limb is painful

Why might a horse have an externally rotated limb?

- paddling

How does a horse with a toed in limb walk?

- swing in toward midline

- interference with contralateral limb

How does a horse with a toed out limb walk?

a. cow hocked (external rotation)

b. cow hocked, base narrow

c. base narrow (postural)

d. base wide (postural)

e bow legged (internal rotation = more prone to arthritis)

What are these flaws of the hindlimb? Which are postural rather than conformational?

- yes

- supports limb loading and proper movement

Is this an ideal pastern angle? Tell us about it.

- no it's a upright pastern angle

Is this an ideal pastern angle?

- short stride length

- prone to navicular disease and pastern osteoarthritis

- causes stress at the coffin bone

This horse have a upright pastern angle, what is seen with it?

- no, its a sloping pastern angle

Is this an ideal pastern angle?

- longer stride length

- prone to soft tissue injuries such as suspensory ligament injury

This horse have a sloping pastern angle, what is seen with it?

- conformational faults are not synonymous with lameness.

- however often contribute to altered limb loading and movement thus increased risk for musculoskeletal injuries

Why is confirmation important?

- often a sign of MSK pain or neurologic disease

What is the importance of altered posture?

16: carpus

D. radiocarpal joint

E. midcarpal joint

F. carpometacarpal joint

G: metacarpophalangeal joint (fetlock joint)

H: proximal interphalangeal joint (pastern joint)

I: distal interphalangeal joint (coffin joint)

What are the joints of the thoracic limb?

D. radiocarpal joint = most mobile with 90* of flexion

E. midcarpal joint = 40* of flexion

F. carpometacarpal joint = 0* of flexion

What is the mobility of the joints of the carpus like?

- an anatomical mechanism of the equine limb that allows the animal to stand with little muscular effort; includes many muscles, ligaments, and tendons

What is the stay apparatus of the forelimb?

light blue = common digital extensor in forelimb and long digital extensor tendon in rear limb

yellow = suspensory ligament (body, branches, exensor branches)

red = deep digital flexor tendon

green - distal accessory (check) ligament

dark blue = superficial digital flexor tendon

What are these tendon of the distal limb?

- affected by lacerations or wounds leading to infections, which can be serious

Why is it important to know the synovial structures of the limb?

- each joint has a dorsal (X') and palmar pouch (X)

What are these joint spaces?

1. palmar annular ligament

2. proximal annular ligament

3. distal digital annular ligament

What are these digital annular ligaments in the horse?

- surrounds the SDFT and DDFT

- extends from mid-cannon to mid P2

This is a digital tendon sheath that is abnormal. What is the digital tendon sheath?

- SDFT (9)

- DDFT (11)

- interosseous ligament (13)

- extensor branches and common DET

- distal sesamoidean ligaments (16-18)

What are the components of the stay apparatus of the digit?

a. tibiotarsal joint

b. proximal intertarsal joint

c: distal intertarsal joint

d. tarsometatarsal joint

What are these tarsal articulations?

- tarsocrural joint

What joint has effusion?

- arthritis and other injuries

Why is the motion of a joint important?

- tibiotarsal joint

Which joints of the tarsus are high motion?

- proximal intertarsal joint

- distal intertarsal joint

- tarsometatarsal joint

Which joints of the tarsus are low motion?

- a patellar locking mechanism that works the same as the forelimb stay apparatus

What is the stay apparatus of the pelvic limb?

- suprascapular nerve

This horse has sweany shoulder, what nerve is impacted?

a. subscapular n

b. axillary n

c. radial n

d. median n

e. ulnar n

f. suprascapular n

g. musculocutaneous n

h. radial

What are the innervations of these parts of the equine thoracic limb?

a. caudal gluteal n

b. sciatic n

c. tibial n

d. cranial gluteal n

e. femoral n

f. common fibular/peroneal n

What are the innervations of these parts of the equine pelvic limb?

1. lateral palmar n

2. medial palmar n

3. medial digital n

4. lateral digital n

5. dorsal branch

What are these nerves of the distal limb, that are important for nerve blocks?

True

True or false

this is a radial nerve issue

- tibial nerve

This horse can't extend its distal limb, which nerve could be impacted?