The Fetlock and Digit

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The Fetlock and Foot
First Year Anatomy
Nicholas Urbanek, BVMS, MRCVS
What is the Fetlock?
• Fetlock is the common name for the
metacarpophalangeal and metatarsophalangeal
joints (MCPJ and MTPJ) of the horses.
• It is formed by the junction of the third
metacarpal (forelimb) or metatarsal (hindlimb)
bones (cannon bones) proximally and the
proximal phalanx (pastern bone) distally.
• Paired proximal sesamoid bones articulate with
the palmar or plantar distal surface of the third
metacarpal or metatarsal bones and are rigidly
fixed to the proximo-palmar /-plantar edge of
the proximal phalanx.
Common Views
Lateral
Lateral
DP
DMPLO
DLPMO
Lateral View
• A: Third MC/MT bone
• B: Proximal phalanx (P1)
• 1: Sagittal ridge
• 3: Palmar process of
proximal phalanx
• 4: Condyles of third
metacarpal bone
• 5: Proximal sesamoid
bones
Dorso-palmer/-plantar (DP)
• A: Third MC/MT bone
• B: Proximal phalanx
• C: Medial proximal
sesamoid bone
• D: Lateral proximal
sesamoid bone
• E: Metacarpo(tarso)phalangeal joint
• J: Depression for medial
collateral ligament
attachment
• 1: Sagittal ridge
Obliques – A Review
• The view is named for the projection of the beam.
• Typically taken at 45 degree angles off the sagittal axis
of the limb.
• Markers must be in place, otherwise unable to
distinguish medial from lateral side.
• Dorsomedial-palmarolateral (plantar)oblique (DMPLO)
• Dorsolateral-palmaromedial (plantar)oblique (DLPMO)
DLPMO
A: Third MC/MT bone
B: Proximal phalanx
C: Medial proximal sesamoid bone
D: Lateral proximal sesamoid bone
E: Metacarpo(tarso)-phalangeal joint
1: Sagittal ridge
3: Palmar process of proximal phalanx/Lateral
palmar tubercle (eminence)
6: Medial condyle of third MC/MT bone
DLPMO
Dorsal
Lateral
Medial
Palmar/Pl
DMPLO
A: Third MC/MT bone
B: Proximal phalanx
C: Medial proximal sesamoid bone
D: Lateral proximal sesamoid bone
E: Metacarpo(tarso)-phalangeal joint
1: Sagittal ridge
2: Lateral condyle of third metacarpal/tarsal bone
3: Palmar process of proximal phalanx
DMPLO
Dorsal
Lateral
Medial
Palmar/Pl
Fetlock
Forelimb
vs
Hindlimb
Bulging 
• The MT is convex at its distal aspect
DP view - Forelimb
The proximal sesamoid bones
are higher
DP view - Hindlimb
The proximal sesamoid bones
are more triangular
Foot or Distal Limb
•
Composed of four bones
– Proximal, middle, distal (first, second, and third) phalanx
– Navicular bone
•
Multiple views obtained
– Lateral
– Dorsopalmar(plantar) view
– Dorsoproximal-palmar(plantar)odistal oblique
•
“Upright Pedal” or “High coronary”
– Palmar(plantar)oproximal-palmar(plantar)odistal
•
“Skyline Novicular”
– Other oblique views
•
•
The foot should have no shoe, be trimmed, and sulci should be packed with PlayDoh
Marker always to the lateral side…can not tell laterality otherwise
Lateral view
A: Middle phalanx
B: Third phalanx
C: Navicular bone
1: Proximal interphalangeal joint
2: Distal interphalangeal joint
3: Extensor process
4: Dorsal surface
5: Palmar process
Dorsopalmar(plantar) view
R
6
A
C
B
7
A: Middle phalanx
B: Distal phalanx
C: Navicular bone
6: Proximal interphalangeal joint
7: Distal interphalangeal joint
Dorsoproximal-palmar(pl)odistal
oblique view
A
R
2
5
5
B
6
7
Dorsoproximal-palmar(plantar)odistal oblique view
A: Middle phalanx
B: Third phalanx
C: Navicular bone
1: Proximal interphalangeal joint
2: Distal interphalangeal joint
3: Extensor process
4: Dorsal surface
5: Palmar process
6: Vascular channel
7: Solar margin
“Upright pedal”
“High coronary”
Palmaro(plantar)oproximalpalmar(plantar)odistal oblique view
“Skyline Novicular”
C: Navicular bone
3: Articular surface
8: Palmar aspect of middle phalanx
9: Nutrient foramen
10: Sagittal ridge
11: Articulation between navicular bone
and middle phalanx
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