Skeletal structure of the Equine Forelimb


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  • this is an excellent resource for equine anatomy
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  • excellent atlas. is there an online version available to the public?
    Also, is there a specific name for the groove in proximal P1 that articulates with the intermediate ridge of distal MC3?
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Skeletal structure of the Equine Forelimb

  1. 1. University of Liverpool,School of Veterinary Science Enter Created by Mr P P Tomlinson Liverpool Veterinary Student
  2. 2. Welcome to “Skeletal Structure of the EquineForelimb” this resource has been created aspart of the “Online Veterinary AnatomyMuseum” (OVAM) in conjunction withLiverpool Vet School.It aims to provide a detailed guide to therelevant bony landmarks present on the equineforelimb (Chapter One) and also highlightcertain ligaments and tendons, particularly inreference to the joints (Chapter Two). Previous Next
  3. 3. Every slide is accessible through the “Resource Map”. The “Resource Map” can be accessed from any slide using the “Resource Map” button Resource Map PreviousNavigate through the slides using the “Next”/”Previous” buttons NextWhere extra detail is available on the slide a “Labels” button will be present, click this to access it, when all available detail is shown the “Labels” button will disappear. Then use the “Next” button. (Occasionally there Labels will be a “Page 2” button, it functions the same way as “Labels”However, the “Next” button can also be used to skip onto the next slide without viewing any extra detail NextFor many of the slides there are extra slides containing some textual information, these can be accessed using the “Information” button To return to the previously viewed slide, a button like the one shown on the right will be present, this is particularly needed for returning to the main detail after viewing an information slide Please note: all available buttons will appear in this bottom toolbar Previous Next
  4. 4.  Forelimb Overview  Distal Phalanx: Dorsal View  Scapula: Lateral View  Distal Phalanx: Cranial View  Scapula: Medial View  Distal Phalanx: Ventral View  Humerus: Lateral View  Distal Phalanx: Caudal View  Humerus: Medial View  Hoof: Dorsal View  Humerus: Cranial View  Hoof: Ventral View  Humerus: Caudal View  Information Slides  Radius and Ulna: Lateral View  Scapula Information  Radius and Ulna: Medial View  Humerus Information  Radius and Ulna: Cranial View  Condyle: Cranial View  Radius and Ulna: Caudal View  Condyle: Caudal View  Carpus  Radius and Ulna Information  Carpal Bones  Carpus Information Manus Overview  Metacarpal Region Information  Below the Carpus  Proximal Phalanx Information  Metacarpal Region  Middle Phalanx Information  Proximal Paired Sesamoids  Navicular Bone Information  Proximal Phalanx  Distal Phalanx Information  Middle Phalanx  Navicular Bone Chapter Two Start
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  12. 12. Note: The proximal and distal parts of the ulna are fused to the radius. The lateral styloid process is the fused distal portion of the ulna. The body of the ulna is absent.Resource Map Labels Previous Next
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  31. 31. • The equine scapula has no acromion process • Due to the position of the scapular spine there is a large infraspinous fossa • There is a central tuberosity on the scapular spine • Well developed supraglenoid tubercle and coracoid process • The supraglenoid tubercle is separate from the glenoid cavity • Extensive scapular cartilage when compared to other speciesResource Map
  32. 32. • The equine humerus is quite horizontal in comparison to that of the dog and cat • The greater tuberosity is split into a larger cranial portion and a smaller caudal portion • The musculospiral groove is relatively deep • The deltoid tuberosity is large • Well-developed epicondyles • Unlike the dog/cat, the horse has no supratrochlear/ supracondylar foramen • The Presence of an intermediate tubercle results in the formation of a double inter-tubercular grooveResource Map
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  34. 34. Note: The olecranon fossa receives the anconeal process of the ulna when the elbow joint is extendedResource Map Labels
  35. 35. • Prominent tuberosities on the radius allow for the • The proximal quarter ligaments and the biceps muscle insertion of collateral of the radius is held to the ulna by ligaments, beyond this the two bones are fused • Grooves for the extensor tendons are present on the • The distal third/half of the ulna fails to form apart from cranial portion of the distal extremity of the radius the lateral styloid process • Fusion of the radius and ulna result in a lack of pronation • The lateral styloid process(Unlike distal extremity of the or supination at this level (fused the dog and cat where ulna) will appear in foals as a secondary ossification the interosseus space allows for a large amount of centre pronation and supination) • There is a small interosseus space at the proximal radio-ulnar notch through which blood vessels pass. Beyond this the ulna is either fused with the radius or fails to developResource Map Page 2
  36. 36. • There is a two row arrangement • The proximal row comprises of the ulnar carpal bone, intermediate carpal bone, radial carpal bone and the accessory carpal bone. • The distal row comprises of the 4th carpal bone, 3rd carpal bone and 2nd carpal bone. The 1st carpal bone is generally absent, however, if present it will be very small and easy to mistake for a fracture • The accessory carpal bone articulates with both the radius and the ulnar carpal boneResource Map
  37. 37. • The third metacarpal is the functional weight bearing bone of this region. The second and fourth metacarpal bones are also present in the form of splint bones • MC3 articulates proximally with the carpal bones and distally with the proximal sesamoids and proximal phalanx • Splint bones also articulate with the carpal bones but taper to a point (known as the button) approximately two thirds down MC3 • The buttons are a useful landmark for nerve blocks • The junction between MC2 and MC3 is a common location forsplints. Splints are a typical ailment of the equine forelimbResource Map
  38. 38. • The proximal phalanx is often referred to as P1 or the long pastern • Collateral ligaments insert onto palpable tubercles on P1’s surface • The caudal surface is V-shaped to accommodate the oblique sesamoidean ligamentsResource Map
  39. 39. • The middle phalanx is often referred to as P2 or the short pastern • Approximately half of P2 is buried in the hoof • Lateral hoof cartilages lie on both the medial and lateral sides of P2 • The superficial digital flexor tendon (SDF) inserts on the proximal edge of P2 • P2 articulates with both the distal phalanx and the Navicular boneResource Map
  40. 40. • An unpaired boat-shaped bone that articulates with both P2 and P3 • The deep digital flexor tendon runs over its palmar surface NAVICULAR DISEASE • Navicular disease is a complex condition with a wide variety of suspected causes • Ultimately it is a long term degenerative condition of both the navicular bone and bursa • It is the most common causes of long term forelimb lamenessResource Map
  41. 41. • The distal phalanx is also known as P3 or the coffin bone, it articulates with P2 and the navicular bone to form the coffin joint LAMINITIS •Laminitis involves inflammation of the sensitive lamina that secure the bones of the distal limb extremity to the hoof wall • This inflammation leads to separation of the sensitive lamina from the interdigitating insensitive lamina • The distal phalanx will then rotate due to the pull of the deep digital flexor. The tip of the distal phalanx will eventually penetrate the soft horn of the soleResource Map
  42. 42. • The hoof covers and protects the distal extremity of the digit• The hoof is formed from keratinized epithelium secreted by the modified dermis covering the distal extremity of the digit• Expansion of the hoof dissipates pressure helping to prevent concussive damage on impact• The join between skin and hoof is called the coronet• The sole of the hoof lies between the wall and the frog• The white line is the junction between the sole and the wall of the hoof, shoe nails are driven into the outer edge of this line• The concave surface means that only the frog and wall make contact with the ground• The frog is a wedge-shaped projection into the sole, with its base set between the two heels. The caudal end of the frog extends over the heel and is known as the heel bulb, and the groove between the frog, bar and the sole is called the paracuneal grooveResource Map
  43. 43.  Joints of the Forelimb Overview  Information Slides  Shoulder Joint  Shoulder Joint Information  Elbow Joint  Elbow Joint Information  Carpal Joints  Carpal Joint Information  Fetlock Joint  Fetlock Joint Information  Ligaments of the Fetlock/Pastern Joints  Pastern Joint Information  Coffin Joint  Coffin Joint Information  Annular Ligaments  Annular Ligaments Information Chapter One Start
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  52. 52. • Although a ball and socket joint,the shoulderactually functions more like a hinge joint • The tendons of supraspinatus and infraspinatus act as collateral ligaments supporting the joint • Supraspinatus tendon splits forming attachments with the lesser tuberosity and the cranial portion of the greater tuberosity. • Bicepsbrachii originates from the supraglenoid tubercle by way of a grooved cartilaginous tendon. This tendon is supported by the intertubercular bursa (biceps bursa) • Bursa and tendon are held in place by the transverse humeral ligament and then overlaid with the aponeurosis of the deep pectoral muscleResource Map
  53. 53. • Typically described as a “snap” joint, where while standing the joint is very stable but on flexion becomes more movable. • This is due to two specific anatomical features: • The humeral condyles have unequal curvature, this means the radius of the central portion is greater than the radius of the cranial and caudal parts (highlighted in previous slide) • The medial and lateral collateral ligaments have eccentric insertions on the humerusResource Map
  54. 54. • • A common outer fibrous capsulejoint comprises of: As a compound joint, the carpal surrounds the overall joint and each individual joint is surrounded by an innerradiocarpal (antebrachiocarpal) joint, • The synovial pouch which is between the radius and the proximal • Collateral ligaments The present on the medial and carpal bones. are majority of the movement lateral occurs here surfaces extending from the radius to the metacarpals • The intercarpal (middle carpal) joint, which is • The carpal canal is occupied by the superficial and between the two rows of carpal bones deep digital flexor tendons surrounded by a common • The carpometacarpal joint between the distal synovial sheath carpal bones and the metacarpals. Here • The accessory carpalminimal palmar carpal movement is ligament, ligament and flexor retinaculum all oppose over extension of the carpusResource Map Page 2
  55. 55. • The joint between metacarpal three, the proximal phalanx and the proximal palmar sesamoids • The main ligaments of this joint are shown on the previous slide • Of particular importance is the proximal extension of the thick palmar ligament. This approximately 2cm enlargement serves a number of functions • Increases the bearing surface for the flexor tendons • Supports the flexor tendons during over extension of the fetlock • Prevents bone to bone contact during flexion of the fetlock when the sesamoids move up along the condyles of MC3Resource Map
  56. 56. • The joint between the long pastern (P1) and the short pastern (P2) • This particular joint has fairly restricted movement • Paired axial and paired abaxial palmar ligaments extend from P1 to the fibrocartilage of P2 • These ligaments oppose over extension of the joint, the straight sesamoidean ligament also aids thisResource Map
  57. 57. • The coffin joint involves P2, P3 and the navicular bone • There is very little movement at this joint • The collateral ligaments between P2 and P3 are short and thick • The navicular bone is held in place by collateral navicular ligaments, a proximal navicular ligament and a distal navicular ligamentResource Map
  58. 58. • The annular ligaments hold the flexor tendons in place • They are formed from localized thickened fascia • The palmar annular ligament attaches the abaxial borders of the sesamoids to the superficial digital flexor tendons • The proximal digital annular ligament is X-shaped when seen in a palmar view • The distal digital annular ligament is U-shaped when seen in a palmar view. It arises from the proximal phalanx and covers the collateral navicular ligament. It also separates the deep digital flexor tendon from the digital cushionResource Map