S&F Of The Shoulder And Brachial Regions

Question 1

What are the regions of the forelimb?

What bones/joints do they consist of?

Answer 1

1. Omo (shoulder)
   - Bones: scapula (plus clavicle in cats)
   - Joints: ends at shoulder joint
2. Brachium (arm)
   - Bones: humerus
   - Joints: begins at shoulder joint, ends at elbow joint
3. Antebrachium (forearm)
   - Bones: radius and ulna
   - Joints: begins at elbow joint, ends at carpal joint
4. Carpus (wrist)
   - Bones: carpal bones
   - Joints: carpal/intercarpal joint
5. Manus (hand)
   -Bones: metacarpal bones
   - Joints: begins at carpal joint, ends at metacarpophalangeal joints
6. Digit (toe)
   - Bones: Phalanges
   - Joints: interphalangeal joints

Question 2

What are the major anatomical features of the scapula?

Answer 2

Scapula is a type of flat bone

Lateral surface:
-> spine (in centre)
-> supraspinous fossa (cranial to spine)
-> infraspinous fossa (caudal to spine)
-> acromion process

Glenoid cavity:
-> articular surface (shoulder joint)
-> concave
-> smooth surface

Supraglenoid cavity:
-> attachment of biceps brachii muscle

Medial/costal surface: serrated, rough bone
-> attachment of serratus ventralis muscle (dorsal) & subscapularis muscle (ventral)

2 centres of ossification: body and supraglenoid tubercle

Question 3

What bony structures of the scapula can we palpate in live animals?

Answer 3

-> dorsal border
-> cranial border
-> cranial angle
-> spine
-> acromion (guide for locating shoulder joint)

-> caudal border beneath muscle so difficult to palpate

Question 4

What are the main extrinsic muscle groups involved in shoulder movement?

• origins, insertion, innervation

Answer 4

1. Brachiocephalic muscle:
   - Origin: cervio-thoracic fascia
   - Insertion: humerus (aponeurosis)
   - Function: protractor
2. Omotransversarius
   - Origin: transversing wing of the atlas (C1)
   - Insertion: acromion process
   - Function: protracts the limb
3. Latissimus dorsal muscle
   (“Broadest muscle of the back”)
   - Origin: thoracolumbar fascia
   - Insertion: humerus (aponeurosis)
   - Function: protractor/propulsion
4. Serratus ventralis muscle:
   Located between muscle and trunk
   - Origins: thoracic wall (ribs) & cervical vertebrae (neck)
   - Insertion: proximal scapula (medial aspect)
   - Function:
   -> cranial portion = retractor
   -> caudal portion = protractor
5. Trapezius muscle:
   - Origin: cervicothoracic fascia
   - Insertion: proximal scapular spine
   - 2 parts: cranial & caudal
6. Rhomboideus muscle:
   (Lies deep to trapezius)
   - Origin: cervicothoracic fascia
   - Insertion: dorsal border of scapula
   - Function: abductors of limb
7. Pectoral muscles:
   - Origin: sternum
   - Insertion: humerus
   - 2 heads: deep & superficial
   - Function: adductor of limb

Question 5

What are the main intrinsic muscles involved in movement of the forelimb?

Answer 5

All other forelim muscles = intrinsic

Origin AND insertion within appendicular skeleton

No effect on limb relative to trunk

Function: move joints within limb
-> flexion
-> extension

Question 6

What are the major anatomical features of the humerus?

Answer 6

*Proximal end

Head:
-articular surface, convex & smooth surface
- articulates with glenoid cavity of scapula at shoulder joint

Greater tubercle:
-lateral aspect
Lesser tubercle:
- medial aspect

Intertubercular groove:
- smooth bone surface
- tendon of origin of biceps brachii muscle passes through this structure

*Distal end

Condyle:
- 2 halves - Medial epicondyle (larger) & latera epicondyle (smaller)
- articular surface (elbow joint) divided into 2 areas
-> Trochlea - pulley like structure; larger; central depression; articulates with radius & ulna
-> Capitulum - smaller; located laterally; articulates with radius

*Olecranon/Ulnar fossa (caudal) & Radia fossa (cranial)
- proximal to articular surfaces

*Supratrochlear foramen:
- nothings passes through
- may not be present in short legged dogs

Question 7

How can you distinguish between a canine and feline humerus?

Answer 7

Proximal end:
- feline features and articular surfaces same as canine

Distal end:
- both have olecranon fossa and radial fossa
- felines do not have a supratrochlear foramen

Felines have a supracondyloid foramen (vulnerable in fractures) through which passes;
-brachial artery
-median nerve

Question 8

Where are the centres of ossification in the humerus?

Answer 8

5 in total;

Proximal epiphyses =1

Body = 1

Condyle = 3
- medial epicondyle
- medial half of the condyle
- lateral half of the condyle

Question 9

What are the palpation landmarks of the humerus?

Answer 9

-> Greater tubercle (guide for locating shoulder joint)

-> Lateral epicondyle

-> Medial epicondyle