Lecture 1 - Equine MSK Anatomy and Conformation

Topographic anatomy

Directional Terms and Body planes

Conformation

the shape or structure of something

Conformational Features

Size, shape, height, angles, contours, transitions, relative proportions, left-right symmetry, muscle development, breed standards

Ideal conformation

provides broad base of support, equal weight bearing across all limbs

Why is conformation important?

Improper form leads to improper function over time -increased stress on joints, decreased performance

Function of horse affects form

changes in structure

Conformation

symmetry, size, and shape of various body regions relative to each other or in general appearance

- not easily changed/modified

Position

refers to the way someone/something holds their body when standing or sitting

- can modify or train posture

Altered posture

often due to pain, weakness, neurologic deficits

Base wide stance

Conformational fault of the forelimb, induces altered limb loading

- fetlock osteoarthritis

- splint bone disease

Fetlock osteoarthritis

Splint bone disease

interosseous ligament

Base-narrow stance

conformational fault of forelimb

- associated with splint bone disease

- fetlock osteoarthritis

- structural changes/damage if not corrected early

toed out

toed in

base wide

base narrow

external rotation

Toe in conformation leads to what kind of limb movement?

Paddling

Limb conformation of toed out leads to what kind of limb movement?

interference with contralateral limb - legs swinging in

Cow hocked

external rotation of hind limbs

- very common and not associated with lameness

Cow hocked, base narrow

common

Βase narrow

common, postural fault

Base wide

uncommon, postural fault

Bow legged

internal rotation, undesirable, uncommon

Conformational faults of digit

Look at hoof-pastern angle

Ideal conformation and posture

- supports optimal limb loading and movement patterns

- reduces risk for msk injuries

Conformational faults and lameness

not synonymous with lameness but if uncorrected can lead to lameness potentially - often contribute to altered limb loading and movement leading to increased risk for musculoskeletal injuries

What is often a sign of musculoskeletal pain?

altered posture

- could also be sign of neurologic disease like ataxia or weakness

Forelimb

Hind limb

D?

Radiocarpal joint

E?

Midcarpal joint

F?

Carpometacarpal joint

G?

Fetlock joint or Metacarpophalangeal joint

H?

Pastern joint or Proximal interphalangeal joint

I?

Coffin joint or Distal Interphalangeal joint

Carpal articulations

Distal forelimb composed of

3rd metacarpal bone bordered by 2nd and 4th metacarpal (splint) bones, Fetlock joint and proximal sesamoid bones, pastern joint, and coffin joint with distal sesamoid bone (navicular bone)

Stay apparatus of the forelimb

opposing angle of joints and tendons/ligaments work together

Light blue?

common digital extensor tendon

Yellow?

Suspensory ligament - body, medial and lateral branches, extensor branches

Red?

Deep digital flexor tendon

Green?

Distal accessory (check) ligament

Dark blue?

Superficial digital flexor tendon

A?

common digital extensor tendon

B?

Lateral digital extensor tendon

4, D?

Interosseus (suspensory ligament)

- medial and lateral branches 4'

1,G?

Superficial Digital Flexor Tendon

2,F

Deep digital flexor tendon

3, F'

Distal accessory (check) ligament (of DDFT)

4?

Digital tendon sheath

Dorsal pouch of fetlock joint?

1'

Palmar pouch of fetlock joint?

1

Dorsal pouch of pastern joint?

2'

Palmar pouch of pastern joint

2

Dorsal pouch of coffin joint?

3'

Palmar pouch of coffin joint?

3

Navicular bursa?

5

Palmar annular ligament?

A

Proximal digital annular ligament?

B

Distal digital annular ligament?

C

What is the digital tendon sheath?

surrounds SDFT and DDFT, extends from mid-cannon to mid P2

Superficial digital flexor tendon?

9

Deep digital flexor tendon?

11

interosseus ligament?

13

Extensor branches of interosseus ligament?

15

Common digital extensor tendon of interosseus ligament?

12

Distal sesamoidean ligament - straight?

18

Oblique distal sesamoidean ligament?

17

Cruciate distal sesamoidean ligament?

16

Pelvic limb articulations

Stifle joint

Patellar ligaments

• Medial: Patellar fibrocartilage, Medial trochlear ridge

• Intermediate (middle)

• Lateral

Femoropatellar joint (top R)

Femorotibial joints

• Medial, lateral

Patellofemoral ligaments

Collateral ligaments -

• Medial, lateral

Cruciate ligaments

• Cranial, caudal

Menisci

• Medial, lateral

• Meniscal ligaments

Pelvic limb stay apparatus

Tarsal articulations

- Distal tibia: Tarsocrural (tibiotarsal) joint (cochlea of distal tibia, trochlea of talus)

- Proximal row of tarsal bones: proximal intertarsal joint

- Intermediate row of tarsal bones: distal intertarsal joint

- Distal row of tarsal bones: tarsometatarsal joint

- metatarsus

Forelimb arteries

Axillary a.

- Subscapular a.

Brachial a.

- Transverse cubital a. (cranial)

- Collateral ulnar a. (caudal)

- Common interosseous a.

Median a.

Medial palmar a.

Palmar digital arteries

- Terminal arch

Thoracic limb innervation

Pelvic limb innervation

Nerves of distal limb

Palmar metacarpal nn.

- medial, lateral

- communicating branch

Palmar digital nn.

- medial, lateral

Dorsal branches

- medial, lateral