JOINT - II Thoracic Limb a. Scapula Review a b. Glenoid cavity (I) c. Supraglenoid tubercle c d. Acromion (I) a b e. Humerus f. Humeral head (I) 3 d g. Greater tubercle (II) h. Lesser tubercles (I) c E*

B. Infraspinous tendon f E. Synovial sheath g 1* I. Infraspinatus bursa h G. F. Transverse capsule humeral lig. e I. , C. Subscapular tendon lateral view 2 II. Shoulder joint, 1. ^Glenohumeral (medial and lateral) (I): thickenings of the joint capsule, they strengthen the joint medial view capsule, but are not true collateral ligaments. * E. Biceps brachii tendon e D 2. ^Coracobrachialis m. (II) 3. ^Coracoid process (II) * Defined in text or legend Review, on individual bones and an articulated skeleton, E. Synovial sheath of the biceps brachii tendon/intertuber- the bones and processes making up the shoulder joint cular sheath (II): an extension of the roomy shoulder joint (see box). capsule around the tendon of the biceps brachii m. in the A. Shoulder joint (glenohumeral, scapulohumeral, or hu- intertubercular (bicipital) groove of the humerus. meral#) (I): a ball-and-socket (spheroid/universal) type F. Transverse humeral (II): attaches to the greater between the glenoid cavity and the humeral and lesser tubercles to hold the biceps brachii tendon in head. Functionally, a freely movable joint, it is chiefly used the intertubercular (bicipital) groove. as a hinge joint, allowing flexion and extension. Having Transect the tendon of the subscapularis m. at the level of no true collateral ligaments, the muscles (especially the the shoulder joint. Observe: infraspinatus m. laterally and subscapularis m. medially) G. Shoulder joint capsule (II): the dense connective tissue crossing this joint take the place of collateral ligaments enveloping the shoulder joint. and provide enough support so shoulder luxation is rare Inject fluid into the capsule to see that it is very disten- in the dog. sible. Return to the proximal end of the right limb and dissect out Incise the shoulder joint capsule and manipulate the limb to the : find the shoulder joint. Twist the humerus to visualize: Reflect the slips of the brachiocephalicus, superficial pectoral, H. Hyaline cartilage (I): the shiny, bluish articular cartilage and deep pectoral mm. laterally. over the head of the humerus and the glenoid cavity. Scrape the deep pectoral and supraspinatus mm. off the Optional: Relocate the bursa under the cut tendon of inser- lesser tubercle of the humerus to expose the bicipital tion of the infraspinatus m.: groove, the large tendon in it, and the ligament holding I. Infraspinatus bursa (I): represented by the shiny surface this tendon down. on the greater tubercle under the tendon of insertion of Locate the main replacements for the collateral ligaments the infraspinatus m. the shoulder lacks: CLINICAL: B. Infraspinous tendon (cut) (I) • Osteochondrosis: a failure of C. Subscapular tendon (cut) (II) cartilage maturation (it grows D. Intertubercular (bicipital) groove (II): the sulcus be- thicker than synovial fluid nutri- tween the greater and lesser tubercles holding the biceps tion supply and deep cartilage brachii tendon. cells die). Trauma may cause E. Biceps brachii tendon: arises from the supraglenoid cracking and dissecting a piece of tubercle, it passes through the bicipital groove where it is cartilage ("joint mouse") into the held down by the transverse humeral ligament. synovial space (osteochondrosis dissecans). This is most # Humeral is the preferred name for the shoulder joint by the Nomina Anatomical Veterinaria (NAV), which makes you wonder why the couldn't have the same NAV name. common on the caudal head of the humerus in dogs.

72 2* II Thoracic Limb JOINT - ELBOW f 7 c Acquired SQ a bursa 8 5* 6* A. Lat. collateral lig.*

b F. Anconeus m. C. Sesamoid bone * 4 e d A* 3* D. Med. collateral lig.* B. Supinator m. 1* 4* I. Left elbow joint, II. Left elbow joint, cranial view g lateral view

a. Humeral condyle (II) 1. Interosseous ligament (II): connects (pivot) articulation, allowing supination the trochlear notch of the ulna and pronation. The distal one is a plane b. Medial epicondyle (I) the radius and ulna in the proximal half of 6. ^Capitulum (I): articulates with the interosseous space type joint. the head of the radius c. Lateral epicondyles (II) 2. Tricipital (olecranon) bursa (II): 4. Annular ligament of the elbow: 7. Biceps brachii m. (I) attaches to the ulna and forms a sleeve d. Head of the radius (II) between the insertions of the tendons of (I) around the head of the radius, allowing 8. Brachialis m. e. Trochlear notch (II) the heads of the triceps and the olecranon tuberosity rotation, thus, supination and pronation f. Olecranon (II) 3. Radioulnar articulation (II): proxi- 5. ^Trochlea (I): articular surface of the humeral condyle crossed by a groove for g. Interosseous space (II) mal and distal, the proximal is a trochoid G. Joint capsule* Elbow joint (cubital or humeroradioulnar articulation): a the elbow). hinge type of synovial joint allowing flexion and extension. Cut into the joint capsule (if your incision through the an- It is also a compound joint formed between the humerus, coneus m. didn't) to explore the inside of the joint. radius, and ulna. G. Joint capsule: the sac enclosing all three articular Review the parts of the bones making up the elbow joint on parts. All these compartments communicate. individual bones and an articulated skeleton (see box): Probe the joint cavity while flexing the elbow to attempt to A, D. Collateral ligaments (lateral and medial [I]): thick- locate: enings of the joint capsule extending from the medial and H. Anconeal process (p35/G): the beak-like proximal end lateral epicondyles of the humerus distally to attach to the of the trochlear notch which fits in the olecranon fossa of radius and ulna. They restrict movement to flexion and the humerus when the elbow is extended. extension. Finding this will be almost impossible on an embalmed speci- A. Lateral collateral ligament: may contain a sesamoid. men therefore, locate it on a skeleton. Also locate: Transect and reflect the insertions of the biceps brachii and I. Medial epicondyle (p34/H): note it is larger than the brachialis mm. Transect the pronator teres m. at the level lateral one holding the anconeal process. of the joint and reflect. Remove the vessels, nerves, and connective tissue in the area to see: CLINICAL: B. Supinator m. (I): arises from the lateral epicondyle. • Ununited anconeal process: p35. Transect and reflect the supinator m. and feel for a bone • Capped elbow/acquired subcutaneous (SQ) in its tendon. bursa (II): acquired due to trauma between the skin C. Sesamoid bone (I): in the tendon of origin of the supinator and the olecranon, common in large animals (horse and m. on the lateral side of the elbow joint. cattle). D. Medial collateral ligament (I) • Fragmented medial coronoid process: Transect the medial collateral ligament to see: improper development (osteochondrosis) E. Medial coronoid process (p35/H): the clinically signifi- leading to arthritis. cant craniomedial, distal end of the trochlear notch. • Anconeus m.: incised to surgically Locate: to open the elbow joint. F. Anconeus m. (II): the muscle covering the elbow joint • Elbow luxation: occurs on the lateral laterally. side due to the smaller lateral epicondyle. To Incise the anconeus m. in a gentle arch and reflect the replace, flex the elbow and force the anconeal muscle to expose the joint (this is a surgical approach to process over the lateral epicondyle.

73 CARPUS R U II Thoracic Limb E. Short med. F. Short lat. A. Antebrachiocarpal joint collateral lig. collateral lig. a k i R Ca Cr Cu U 2* 4*

Ca Mc I h E F 1* Cr Cu * Ca B. Middle 4 carpal e I. Palmar c joint carpal lig. G. Interosseous space Mc V b 3* H. Carpal canal g f d Mc 5 II. Right carpus, III. Carpus cross section, schematic palmar view C. Carpometacarpal joint* IV. Carpus, palmar view I. Left carpus, D 1. (I): plane joints between the individual a. Extensor retinaculum (III) lateral view carpal bones b. Flexor retinaculum (III) 2. Distal radioulnar joint (I): between the distal radius c. DDF tendon (III) and ulna, it shares a cavity with the antebrachiocarpal joint Review p36 d. Median n. (III) 3. Intermetacarpal joints (I): between the bases (proximal (III) R. Radius ends) of the metacarpal bones e. Ulnar n. U. Ulna 4. Intercarpal, antebrachiocarpal, and carpometa- f. Median a. (III) g. SDF tendon (III) Cr. Radial carpal bone carpal ligaments (II): many small ligaments connecting Cu. Ulnar carpal bone the antebrachial, carpal, and metacarpal bones h. Superficial fascia (III) Ca. Accessory carpal bone Two superimposed sheathes cover the carpus and maintain its i. Common digital extensor tendon (III) integrity. The joint capsule (G) forms the deep sheath. The j. Extensor carpi radialis tendons (III) Mc 1-5. Metacarpals I-V extensor and flexor retinaculae (modified deep carpal fascia) forms the superficial sheath. * Defined in text or legend CARPUS, "": the composite joint between the ante- E, F. Short medial (radial) and lateral (ulnar) collateral brachial, carpal, and metacarpal bones. A modified hinge ligaments (II, III): only cross the antebrachiocarpal joint to (ginglymus) type joint, it allows flexion and extension with stabilize it. Long collateral ligaments are lacking; therefore, some lateral movement. there are no continuous ligaments over all the joints. Review the bones of the carpus on an articulated skeleton G. Interosseous space (II): the void between the metacarpal of the limb (see box and p36). bones. Cut into the joint capsule under the extensor tendons at the Relocate and cut through the flexor retinaculum, if not distal end of the radius to open the most proximal joint: already done. A. Antebrachiocarpal joint (I): the highly movable hinge H. Carpal canal (III): formed by the palmar side of the carpal articulation between the distal radius and ulna and the bones, the medial side of the accessory carpal bone, and proximal row of carpal bones. the flexor retinaculum. Cut into the joint capsule under the extensor tendons, be- Pull the structures passing through the carpal canal aside tween the proximal and distal rows of the carpus: to view the dorsal wall of the carpal canal: B. Midcarpal/middle carpal joint (I): a hinge articulation I. Palmar carpal fibrocartilage/ligament (III): thick, firmly between the two rows of carpal bones. It communicates attached connective tissue forming the distally with the carpometacarpal joint between the third smooth dorsal wall of the carpal canal. and fourth carpal bones. Although less than the antebra- chiocarpal joint, it also allows a great deal of movement. CLINICAL: C. Carpometacarpal joint (I): the plane articulation between • Communication between the 2 distal carpal the distal row of carpal bones and the metacarpal bones joints becomes important when blocking the car- that has a little sliding or gliding movement. Its cavity pus in horses (blocking top two = blocks all). communicates with the middle carpal joint. • Carpal luxation, subluxation of the carpal D. Joint capsule (IV): consists of fibrous and membranous joint: rupture of the palmar carpal ligament and the joint parts. Its fibrous part is common to all the joints, attaching capsule results in a plantigrade stance and to the margins of the radius and metacarpal bones. The nonweight bearing lameness. synovial membranes form three synovial sacs correspond- • Old age laxity of carpus: gradual weak- ing to the joints. The middle and carpometacarpal joints ness of the carpus in old and obese dogs, communicate (distal 2). resulting in a plantigrade stance. No treat- Locate in pictures, don't dissect the following ligaments: ment is needed as the dog does fine.

74 DIGITAL JOINTS II Thoracic Limb R

II. Joints & soft structures 9 I. Joints of manus, of the digit, lateral view dorsal view 7 Mc I Mc V c 10 15 11 A. Metacarpophalangeal b * F. Joint capsule (MP) joint 1 b IV. Carpus, palmar view 4 P1 E. Collateral ligg. F 12 1' B. Prox. interphalangeal 5 (PIP) joint* 1 13 G. Dorsal elastic lig.* 6 P2 12 8 C. Dist. interphalangeal (DIP) joint* P3 8 d R. Radius G d 3 2 Mc I-V. Metacarpal bones 1-5 P1. Proximal phalanx or P1 e P2. Middle phalanx or P2 1. SDF (I) 9. Interosseous m. (I) P3. Distal phalanx or P3 1'. Manica flexoria (I) 10. Extensor branch of interosseous m. (I) 2. DDF (I) 11. Branch of interosseous m. to palmar sesa- 3. Flexor tubercle (I) moid bone (II) a. Proximal sesamoid bones (II) 4. Palmar annular ligament (cut) (I) 12. Distal sesamoidean ligaments (II) (I) b. Dorsal sesamoid bone 5. Proximal digital annular ligament (cut) (I) 13. Palmar pouch (I) c. Dew claw or paradigit (I) 6. Distal digital annular ligament (cut) (I) 14. Dorsal pouch (I) d. Ungual process 7. Common digital extensor tendon (I) 15. Interdigital space (I) e. Horny claw (I) 8. Extensor process of P3 (I) Suspensory apparatus in horses see p71 First, review the bones the digital bones and their relationship hinge joint) with a little rotation and side movement. The to each other with disarticulated bones and an articulated head (distal trochlea) of P1 has two condyles separated by specimen (p38-9). an axial ridge. The axial ridge articulates with the axial Take your disarticulated phalangeal bones and articulate groove on the proximal end of P2. them manually. Note the saddle joint configuration of the C. Distal interphalangeal (DIP) joint (I): the saddle type of articular surface of the distal end of the middle phalanx and synovial joint between the middle and the distal phalanges. the proximal end of the distal phalanx. They fit together like It mainly allows flexion and extension (modified hinge two saddles, one upside down. This allows movement in joint) with a little rotation and side movement to adjust two planes. Manipulate the bones to imitate the possible the paw to irregularities of the ground. movement. D, E. Medial and lateral collateral ligaments (II): stabilize Dissect your cadaver to find the following structures. the sides of all the digital joints (metacarpophalangeal and A. Metacarpophalangeal (MP) joints (I): the synovial ar- phalangeal). ticulations between the metacarpal bones and the proximal F. Joint capsules (I): each digital joint has dorsal (14) and phalanges and palmar sesamoid bones. A modifiedhinge palmar (13) pouches that allow movement of the bones (ginglymus) joint, it allows extension and flexion with slight without tearing the capsules. side to side motion only on extreme flexion. G. Dorsal elastic ligaments: the two elastic structures B. Proximal interphalangeal (PIP) joint (I): the synovial of each distal interphalangeal joint extending from the saddle joint between the proximal (PI) and middle (P II) middle phalanx to the dorsal end of the distal phalanx. phalanges allowing mainly flexion and extension (modified They retract the claw.

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