A18 - Pastern and coffin joints and their muscles in the hindlimb

Question 1

Pastern joint

1. General features
2. Structures/ligaments
3. Draw the joint

Answer 1

• Diarthrosis
• Saddle joint (diaxial)
  
  • ​Movement: ligaments restrict the movements to mainly flexion/extension (hinge joint)
• Art. interphalangeae proximale maus
• Between: Ph1 (covex surface) → Ph2 (concave surface)
• Joint capsule has a dorsal and a plantar pouch

Structures

• Capsulae articulares
  
  • ​Recessus dorsales (injection site)
  • Recessus palmares
• Ligg. collateralia
• Ligg. palmaria axialia (P1 → P2)
• Ligg. palmaria abaxialia
• Scutum medium (formed by straight sesamoideum ligament, axil ligaments, and palmar surface of tuberosita flexoria → passage form DDF)

Question 2

Coffin joint (art. interphalangea distalis)

1. General features
2. Structures/ligaments
3. Draw the joint

Answer 2

• Saddle joint (diaxial)
  
  • ​Movement: flexion - extension (sideways movement are possible)
• Art. composita
• Articulation between:
  
  • Ph2
  • Ph3
  • Distal sesamoid bone/navicular bone
• Retinaculum flexorium

Structures:

• Capsulae articularis
  
  • ​Recessus dorsalis (injection site, under the common digital extensor)
  • Recessus palmaris (under DDF, up to Ph2)
• ​Scutum distale (formed by the flexor surface of the navicular bone, passage for DDF)
• Bursa podotrochleare (between os naviculare → DDF tendon)
• Lig. collaterale laterale (depression on Ph2 → Ph3)
• Lig. collaterale mediale (depression on Ph2 → Ph3​)
• Ligaments of the navicular bone:
  
  • Lig. sesamoideum impar (from distal rim of os naviculare → coffin bone, palamer border of articular surface)
  • Ligg. collateralia sesamoidea (from P1 → coffin bone, hoof cartilage and os naviculare)
• Ligaments of the hoof cartilage:
  
  • Lig. chondrocompedalia (pass between distal end of P1 and proximo-palmar aspect of coffin bone and hoof cartilage)
  • Ligg. chondrocoronaria (connects dorsal extrimity of the cartilage, P2 and ligg. collateralia of the coffin joint)
  • Ligg. chondroungularia (from P3 → hoof cartilage, distal border)
  • Ligg. chondrosesamoidea (between hoof cartilage → corresponding site of os naviculare)
  • Ligg. chondroungularis cruciata (between axial aspect of cartilages → palmar end of opsite angle of P2)
  • Lig. chondropulvinale (fibers that radiate from axial aspect of the hoof cartilages to digital cushion)

Question 3

Draw the pastern and coffin joint

Answer 3

Question 4

Retinaculum flexorium

Answer 4

• Binds the deep digital flexor tendon
• Enforces the carpus on the palmar aspect, forming a continous structure named the digital sheat:
  
  • ​Fuses with:
    
    • Proximal sesamoid bone
    • Plantar ligaments
    • Collateral sesamoid ligmanents
    • Flexor tendons
    • Extensor tendons (dorsally)
    • Ligaments (dorsally)
    • Joint capsules (dorsally)
• On the plantar side, the sheath comprise:
  
  • Lig. anulare plantare (surrounding flexor tendons)
  • Fetlock plate (cartilage plate attached to Ph1, unites flexor tendons to Ph1
  • Ligg. anularia digiti
• Retinaculum extensorium: corresponding structure on the dorsal side
• Bursa podotrochlearis (on the plantar side of Ph3)

Question 5

Give the muscles of the digits on the hindlimb

Answer 5

Extensors:

1. M. extensor digitorum longus​
2. M. extensor digitorum lateralis
3. M. extensor digiti I. [hallucis] longus
4. M. extensor digitalis brevis

Flexors:

1. M. flexor digitalis superficialis
2. M. flexor digitalis profundus
   
   • ​M. flexor digitorum lateralis
   • M. flexor tibialis caudalis
   • M. flexor digitorum medialis
3. M. flexor digitalis brevis
4. Mm. interflexorii (car)
5. Mm. lumbricales (car, eq)
6. Mm. interossei

Question 6

M. extensor digitorum longus

Answer 6

• Origin: Fossa extensoria on condylus lateralis of femur
• Insertion: Processus extensorius of Ph3 of digits II-V.
• Action:
  
  • Extends stifle and joints of digits
  • Flexes tarsus

Question 7

M. extensor digitorum lateralis

Answer 7

• Origin: Proximal third of fibula
• Insertion: Unites with long digital extensor’s tendon to reach digit V. Ph3
• Action:
  
  • Extension and abduction of digit V.
  • Flexes tarsus

Question 8

M. extensor digiti I. [hallucis] longus

Answer 8

Ca?

• Origin: Middle third of fibula
• Insertion: Radiates into fascia over metatarsophalangeal joint of digit II.
• Action:
  
  • Extends digit II. (and digit I. if it’s present)
  • Flexes tarsus

Question 9

M. extensor digitalis brevis

Answer 9

Action: To act as an auxillary extensor of the digits 2, 3 and 4

Question 10

M. flexor digitalis superficialis

Answer 10

• Origin: Fossa supracondylaris of femur, partly fused with m. gastrocnemius caput lateralis
• Insertion: Its tendo plantaris turns from medial to lateral direction around common calcaneal tendon, on the surface of tuber calcanei it makes a cap (galea calcanea), then finally attaches to P2 on plantar surface of digits:
  
  • Ca: Digits 2-5
  • Eq: Digit 3
  • Ru, Sus: Digits 3-4
• Action:
  
  • Flex stifle
  • Extends hock
  • Flexes joints of digits (see insertion)
  • Eq: Part of the passive stay and fixation apparatus

Question 11

M. flexor digitalis profundus

Answer 11

• Consists of three induvidual muscles
  
  1. M. flexor digitorum lateralis
  2. M. flexor tibialis caudalis
  3. M. flexor digitalis medialis

M. digitorum lateralis

• Origin:
  
  • ​Proximal caudal half of fibula
  • Proximal caudolateral border of tibia
  • Membrana interossea
• Insertion:
  
  • ​Plantar surface of Ph3 of digits 2-5, on tuberculum flexoria (eq: on facies flexoria)
• Action:
  
  • ​Flexes digital joints
  • Auxiliary extensor of the hock joint
• Innervation: N. tibialis
• Blood supply: A. caudalis femoris distalis

M. flexor tibialis caudalis

• Origin: Caput fibulae, caudally
• Insertion:
  
  • ​Ca: Tarsus, medially (radiates into tarsal fascia)
  • Other domestic mammals: Joins the deep digital tendon
• Action: Extends tarsus

M. flexor digitalis medialis

• Origin: Tibia, caudoproximally
• Insertion:
  
  • ​Tuberculum flexoria on the plantar surface of the distal phalanx of digit 2-5
  • Eq: fascies flexoria
• Action:
  
  • ​Flexes digital joints
  • Auxiliary extensor of the hock joint
• Innervation: N. tibialis
• Blood supply: A. caudalis femoris distalis

Question 12

M. flexor digitalis brevis

Answer 12

Car

• Origin: The dorsal surface of the superficial digital flexor tendons
• Insertion: With the tendons of the deep digital flexor
• Action: Assist in flexing the digits

Question 13

Mm. Interflexorii

Answer 13

Car

• Origin: The tendon of the deep digital flexor with the suspensory ligament of the pad
• Insertion: The tendons of the superficial digital flexor, more distally
• Action: Act as an auxilary flexors of the digital joints

Question 14

Mm. lumbricales

Answer 14

Car, eq

• Origin: The abaxial borders of the tendons of the deep digital flexor
• Insertion: The proximal ends of the 1^st phalanges of digits 3-5
• Action: To flex the first digital joint

Question 15

Mm. interossei

Answer 15

• Origin: Proximal part of the metatarsals
• Insertion: On the sesamoid bones of the first digital joint
• Action: To flex the metacarpalphalangeal joint of the supporting digits in ca and sus