📝 STANDARD DESCRIPTION:
Ox Metatarsus:
- Cannon Bone = fused Mt III + Mt IV (just like forelimb cannon).
- Slightly LONGER and more 4-sided than metacarpal cannon (way to tell front from back!).
- Vestigial Mt II + Mt V usually small or absent.
Digits (Ox):
- 2 functional digits (III & IV) — cloven hoof.
- 2 dewclaws (digits II & V) — non-weight-bearing.
- Each functional digit has 3 phalanges (P1-P2-P3) + proximal sesamoids (2) + distal sesamoid (navicular) (1).
- P3 is the cloven hoof bone (os ungulare).
Hindfoot vs Forefoot of Ox:
- Hind cannon LONGER & more square in cross-section.
- Front cannon shorter & rounder.
📚 DETAILED DESCRIPTION:
METATARSUS — CANNON BONE OF HINDLIMB
Like the forelimb, the bovine metatarsus is the fused Mt III + Mt IV = 'cannon bone'. The fused bone has a dorsal longitudinal groove showing where the two original bones met. Distally it splits into two trochleae for the two digits.
How to tell hindlimb cannon from forelimb cannon:
• Hindlimb (metatarsal) cannon: LONGER, more SQUARE in cross-section.
• Forelimb (metacarpal) cannon: SHORTER, more ROUNDED.
Vestigial Mt II and Mt V (the splint-like bones) are usually small buttons or absent.
DIGITS — same plan as forelimb:
• 2 functional digits (III, IV) — together they form the cloven hoof.
• 2 dewclaws (II, V) — small, non-weight-bearing nubs above and behind the fetlock.
• Each functional digit has:
– P1 = proximal phalanx (long pastern bone)
– P2 = middle phalanx (short pastern bone)
– P3 = distal phalanx (coffin bone / os ungulare) — encased in the hoof horn
– 2 proximal sesamoids at the fetlock
– 1 distal sesamoid (navicular) behind P3
HOOF: The horn capsule covering P3. Each functional digit has its own claw → bovine 'cloven hoof'.
// COMPARATIVE ANALYSIS
| HORSE |
1 functional digit (Mt III). Mt II + Mt IV are SPLINT BONES. P3 is the coffin bone with retrossal processes; navicular bone present behind it. |
| DOG |
4 functional digits (II-V). Hind dewclaws (digit I) often present in some breeds and may be removed surgically. P3 = ungual crest (claw). |
| PIG |
4 digits on hindlimb — III & IV main, II & V smaller but reach the ground on soft surfaces. |
| FOWL |
TARSOMETATARSUS = single fused bone (distal tarsals + Mt II, III, IV). Usually 4 toes (3 forward + 1 back = anisodactyl). Spur present in cocks on medial side of tarsometatarsus. |
CLINICAL RELEVANCE
Foot Rot (Pododermatitis) in Cattle: Bacterial infection in the cleft between the two claws.
Sole Ulcer / Laminitis (Cattle): Inflammation between hoof horn and P3 → painful lameness.
Navicular Disease (Horse): Chronic inflammation of the distal sesamoid (navicular bone) — major cause of forelimb lameness in horses (less common in hindlimb).
Site for IVRA / 'Bier Block' in cattle hindlimb: Dorsal common digital vein on the hindlimb.
