Pectoral Girdle & Shoulder

BONES


1.1. Identify the components of the pectoral girdle
Clavicle and scapula

1.2. Demonstrate how you would hold the clavicle in anatomical position.
In posterior position, sternal end on the left and acromial end on the right. Corocoid tubercle and costal tuberosity at inferior surface

1.2.1. How is the clavicle different from other long bones in its ossification
Intramembranous ossification, even though it is a long bone. Other long bone ossify endochondrally.

1.2.2. Explain why the conoid tubercle & trapezoid line are important (http://www.getbodysmart.com/ap2/skeletalsystem/skeleton/appendicular/upperlimbs/clavicle/tutorial.html)
Conoid Tubercle: provide attachment for conoid ligament, provides landmark of inferior of clavicle
Trapezoid line: provide attachment for trapezoid ligament
Ans: the 2 parts of the coracoclavicular ligament are attached (the accessory ligament that gives the acromioclavicular joint its strength)








1.2.3. Identify where the major muscles are attached to the clavicle


Posterior side of the clavicle - supraspinous fossa, infraspinous fossa


Anterior side - clavicular fossa


Ans: pectoralis major, deltoid (anterior surace lateral third and periosteum), sternomastoid, trapezius (posterior surgface lateral third), subclavius (inferior surface)





1.3. Identify the scapula and describe how to hold it in anatomical position


http://www.getbodysmart.com/ap/skeletalsystem/skeleton/appendicular/upperlimbs/scapula1/tutorial.html


On an anterior point of view, the medial end is facing the medial region of our body , coracoid process, glenoid cavity is lateral to our vertebrae.





1.3.1. Identify the coracoid process of the scapula.


Inferior to acromion process , lateral to humerus





1.3.1.1. List the structures attached to the coracoid process of the scapula.


Ans: Coracobrachialis, short head of biceps, pectoralis minor, coracohumeral ligament, coracoacromial ligament, coracoclavicular ligament





1.3.2. Identify the scapula angles & medial border


Superior, lateral and inferior angle.


Medial border: Vertebral border





1.3.2.1. On which ribs are the superior & inferior angles related?


T2 - T7





1.3.2.2. Which muscles are attached to the medial border?


Serratus anterior, rhomboid minor and major, levator scapulae, small part of latissimus dorsi





1.3.3. Identify the scapular spine and the fossae related to it


Spine is sandwiched in between supraspinous and infraspinous fossa





1.3.3.1. Trace and identify the landmark at its lateral end.


Glenoid cavity , coracoid process, acromion process





1.4. Identify head, greater and lesser tubercles in the upper end of the humerus.


The lesser tubercle is at the anatomical anterior side of humerus, greater is at posterior, head of humerus is in glenoid cavity








1.4.1. Identify the bicipital groove. What muscles are attached to it?


Slender tendon of long head of bicep muscle, pectoralis major to the lateral lip, teres major to the medial lip and latissimus dorsi to the floor


Ans: pectoralis major to lateral lip; teres major to medial lip; latissimus dorsi to the floor








1.4.2. Outline the anatomical and surgical necks of the humerus on the bone.


Anatomical neck is near the head of humerus


Surgical neck is a constriction below the tubercles of the greater tubercle and lesser tubercle, and above the deltoid tuberosity








1.4.3. What are the key relations of the surgical neck?


Easily fractured compared to anatomical neck, more surgery needed.





MUSCLES





2.1. Do a virtual dissection in 4 D Anatomy (http://4danatomy.com/modules ) to explore the shoulder region : Left Shoulder (upper Lateral View)





2.2. Identify the following muscles around the pectoral girdle: (ANM Upperlimb System 19)


Pectoralis major and minor, Trapezius,Serratus anterior, Rhomboids major and minor, Teres major and minor, Biceps, Coracobrachialis, Triceps





2.3. Explain their actions by their attachments


http://www.getbodysmart.com/ap/muscularsystem/armmuscles/menu/menu.html





2.4. Identify deltoid and its proximal and distal attachments.








Attachments


Origin: (proximal attachments)


Anterior (clavicular) head: upper anterior surface of the lateral ⅓ of clavicle.


Middle (acromial) head: lateral acromion process and spine of the scapula


Insertion: (distal attachments)


Deltoid tuberosity of the humerus





2.5. Explain its actions


http://www.getbodysmart.com/ap2/muscularsystem/armmuscles/anteriormuscles/deltoid/tutorial.html


Flex the arm at the shoulder joint


Medially rotates the arm at the shoulder joint


Abducts the arm at the shoulder joint


Extend arm and rotate laterally


Centre of the triangle: base formed by the lower edge of acromial process and apex by the insertion of the deltoid


Deltoid muscles are well developed in adults and easily accessible, no major vessels


2.6. Identify the rotator cuff muscles.


Teres minor, supraspinatus, infraspinatus, subscapularis


Attached to the greater tuberosity and lesser tuberosity





2.6.1. What are their attachments and actions?


http://www.getbodysmart.com/ap/muscularsystem/armmuscles/menu/menu.html


Subscapularis-


helps to stabilize the head of the humerus in the glenoid fossa during shoulder movements.


Origin: (proximal attachments)


Subscapular fossa of the scapula.


Insertion: (distal attachments)


Lesser tubercle of humerus.





Action: Medially rotates the arm at the shoulder (glenohumeral) joint


Supraspinatus


Origin: (proximal attachments)


Supraspinous fossa of the scapula.


Insertion: (distal attachments)


Superior aspect of the greater tubercle of the humerus.





passes under acromion to attach to the superior of greater tubercle


Actions- Helps the deltoid muscle initiate the abduction of the arm at the shoulder (glenohumeral) joint., Helps stabilize the shoulder by drawing the humerus toward the glenoid fossa of the scapula.


Infraspinatus


provides the mechanical link between the posterosuperior and anterior parts of the rotator cuff.


Origin: (proximal attachments)


Infraspinous fossa of the scapula.


Insertion: (distal attachments)


Middle part of the greater tubercle of the humerus.





Actions- laterally rotates the arm at the shoulder (glenohumeral) joint, Helps stabilize the shoulder by drawing the humerus toward the glenoid fossa of the scapula.


Teres minor


It’s narrow and elongated in shape and sometimes may be fused with infraspinatus. Its main function is to stabilize the humerus in the glenoid fossa when the shoulder moves.


Origin: (proximal attachment)


a. Middle part of the lateral (axillary) border of the scapula.


Insertion: (distal attachment)


a. Inferior aspect of greater tubercle of humerus.





Actions- laterally rotates the arm at the shoulder joint, weakly adducts the arm at the shoulder joint, Helps stabilize the shoulder by drawing the humerus toward the glenoid fossa of the scapula.


2.7. What is a bursa? List the bursae around the shoulder joint.


Subacromial bursae, subdeltoid bursae, subcoracoid bursae, subscapular bursae


Bursa- small fluid-filled sac lined by synovial membrane with an inner capillary layer of viscous synovial fluid (similar in consistency to that of a raw egg white) which provides a cushion between bones and tendons/ muscles around a joint





2.7.1. Identify the subacromial bursa





2.7.1.1. What is its function?


Facilitate the gliding of muscles or tendons over bony or ligamentous surfaces


Facilitates the movements of the deltoid over the fibrous capsule of the shoulder joint and the supraspinatus tendon





2.8. Identify the muscles which move the scapula (ANM Upperlimb System 21)





2.8.1. Demonstrate on each other (your peers) the range of movements possible involving the scapula.


Protraction: scapula moves forwards on the chest wall (punching and reaching forward), Retraction: scapula are drawn backwards in the direction of the median plane in bracing back of the shoulders, Elevation: the scapula is elevated (shrugging)





2.8.2. List briefly the actions of the principal muscles that move the scapula


Ans: Elevation: simultaneous contraction fo the levator scapulae and the upper fibres of the trapezius





Depression: simultaneous contraction of the pectoralis minor, lower fibres of trapezius and latissimus dorsi





Medial: simultaneous contraction of levator scapulae, rhomboids, and latissimus dorsi. The gravity (weight of the upper limb) plays a key role in this movement





Lateral: trapezius and serratus anterior. The glenoid cavity is tilted upwards which is necessary for the abduction of the upper limb above 90 degrees.





Protraction: serratus anterior assisted by the pectoralis minor muscle


Retraction: middle fibres of the trapezius and rhomboids





2.9. Identify and define the boundaries of the quadrangular space. (ANM Upperlimb Regions 12,22)


Ans: superior (above): teres minor posteriorly, inferior (below): teres major, medially: the long head of the triceps branchii, laterally: the surgical neck of the humerus, anteriorly: the subscapularis





2.9.1. What are its contents?


Ans: it transmits the axillary nerve and posterior circumflex humeral vessels (artert and vein)


Axillary nerve, posterior circumflex humeral artery





2.10. Identify and define the boundaries of the triangular space. (ANM Upperlimb Regions 23)


Ans: inferior: the superior border of the teres major, lateral: the long head of the triceps, superios: teres minor or subscapularis








2.10.1. What are its contents?


Circumflex scapular artery


2.10.2. Where does the circumflex scapular artery arise and along with which


other artery?


From the subscapular artery; thoracodorsal artery


2.10.3. Which muscle does that latter artery mainly supply?


Latissimus dorsi





3. JOINTS





3.1. Identify the articulating surfaces of the shoulder joint. (ANM Upperlimb System 11)


3.1.1. Identify the Fibrous capsule of shoulder joint and its thickenings.


Fibrous joint capsule surrounds the glenohumeral joint and is


attached medially to the margin of the glenoid cavity and laterally to the


anatomical neck of the humerus. The intrinsic ligaments are the


thickenings of the fibrous capsule, which strengthen the shoulder


joint.


3.1.1.1. Where is it lax?


The capsule is lax and lies in folds when the arm is adducted





3.2. Identify the Ligaments around the shoulder joint (ANM Upperlimb System 11)





3.2.1. Identify the ligament which reinforces the fibrous capsule.


Coracohumeral ligament


3.2.2. Identify the ligament, located above the joint, that forms a special


structure?


The coracoacromial ligament attaches by its base to the lateral border of the


coracoid process and by its apex to the medial border of the acromion. It


forms coracoacromial arch (coracoid process+coracoacromial ligament +


acromion = coracoacromial arch) above the capsule of the


shoulder joints. It prevents superior displacement of the head of the humerus.


3.2.3. Identify ligament is located below the joint. What is its significance?


Transverse humeral ligament, it converts the groove into canal, which holds


the synovial sheath and tendon of the biceps brachii in place during


movements of the glenohumeral joint.





The transverse humeral ligament attaches to the margins of the bicipital


groove preventing displacement of the tendon of long head of biceps. It forms


the roof of a fibro-osseous tunnel, where the tendon of long head of biceps


can become irritated by friction, resulting in bicipital tendonitis.











http://www.orthosurgery.gr/parousiasis/shoulder/119.pdf





3.3. Draw a table listing the principal movements of the shoulder joint and the important muscles involved in these movements.








Movement


Prime Mover


Synergist



Flexion


Pectoralis major (clavicular head), deltoid (clavicular and anterior acromial parts)


Coracobrachialis (assisted by biceps brachii



Extension


Deltoid (spinal part)


Teres major, latissimus dorsi, long head of triceps brachii



Abduction


Deltoid (as a whole, but especially acromial part)


Supraspinatus



Adduction


Pectoralis major, latissimus dorsi


Teres major, long head of triceps brachii



Medial Rotation


Subscapularis


Pectoralis major, deltoid (clavicular part), latissimus dorsi, teres major



Lateral rotation


Infraspinatus


Teres minor, deltoid (spinal part)



Tensors of articular capsule (to hold head of humerus against the glenoid cavity)


Subscapularis, infraspinatus


Supraspinatus, teres minor



Resisting down-ward dislocation (shunt muscles)


Deltoid


Long head of triceps brachii, coracobrachialis, short head of biceps brachii






3.4. Demonstrate using a volunteer how you will test the movements of the shoulder joint both actively and passively.





3.5. Why is the shoulder joint the commonest joint to dislocate? (anterior dislocation - most common)


The shoulder joint has a shallow socket. The smaller glenoid cavity in comparison with the larger head of humerus causes a lot of instability in the joint.





3.5.1. Explain the factors involved in maintaining joint stability and their relative importance:





Bony articulating surfaces


The glenohumeral joint is the main articulation of the shoulder joint. It


is the multiaxial ball-and-socket synovial joint formed by the articular


surfaces of the glenoid cavity and the head of the humerus. The


glenoid cavity depth is increased by a rim of fibrocartilage that


surrounds it which increases the stability of the joint





Joint capsule & ligaments


The joint capsule at the shoulder is formed by a group of ligaments


that connect the humerus to the glenoid. These ligaments are the


main source of stability for the shoulder. They are the superior, middle


and inferior glenohumeral ligaments, coracohumeral ligaments and


transverse humeral ligaments





http://www.radiologyassistant.nl/en/p4f49ef79818c2/shoulder-mr-anatomy.html


key muscles (rotator cuff)


Your rotator cuff is made up of muscles and tendons that keep the ball


(head) of your upper-arm bone (humerus) in your shoulder socket. It


also helps you raise and rotate your arm. They consist of the


supraspinatus, infraspinatus, teres minor and subscapularis





3.6. Which is the only articulation between the upper limb and axial skeleton? (ANM Upperlimb System 10)


The sternoclavicular joint


3.6.1. How is this joint divided?


Medial and lateral compartments by and intra-articular fibrocartilaginous disc


Articular disc





3.6.2. How is this joint made extremely strong?


Due to the multiple ligaments that hold the joint together such as the costoclavicular ligaments, the intra-articular disc ligament, the interclavicular ligament and the capsular ligament that surrounds the joint


Anterior and posterior sternoclavicular ligament, interclavicular ligament


3.7. What special structure is found in the AC(Acromioclavicular) joint and what is its function? (ANM Upperlimb System 10)


Atypical synovial joint made up of fibrocartilage (articular disc), absorb shock and reduce friction during movement (for articulation too) -> allows anterior and posterior movement of the acromion, rotation & tilting of the acromion


A fibrocartilaginous disc (partial) which divides the join in two, allowing two different movements





3.7.1. Define an intrinsic ligament and identify the intrinsic ligament of the AC joint


Intrinsic ligaments - surround the joint; may be extracapsular(outside capsule)


or intracapsular (inside capsule) - acromioclavicular ligament


A ligament that is a capsular thickening: the acromioclavicular ligament





3.7.2. Define an accessory ligament and identify the the accessory ligament of


the AC joint


Separate ligaments or parts of the joint capsule serve as support strengthens


or supports the primary ligament - Coracoclavicular Ligaments (Conoid and


Trapezoid ligament)


A ligament distant to the joint that gives it stability: coracoclavicular ligament





3.8. Identify the following ligaments and give their functions





3.8.1. coracohumeral ligament.


It attaches to the lateral part of the base of the coracoid process and crosses


the shoulder joint to attach to the anterior surface of the greater tubercle of the


humerus, where it blends with the fibrous capsule of the shoulder and the


tendon of the supraspinatus.


Carries the dead weight of the arm


3.8.2. coracoacromial ligament.


CAL also acts to transmit loads across the scapula. Serving as a tension


band, forces exerted on the coracoid process by the coracobrachialis,


pectoralis minor, and biceps (short head) muscles are transmitted to the


acromion; attaches the coracoid process with the acromion process


Arches over the shoulder joint, helping to prevent superior dislocation and


stabilize the supraspinatus


3.8.3. transverse humeral ligament.


Holds the tendon of the long head of biceps brachii muscle in the groove


between the greater and lesser tubercle on the humerus (intertubercular


sulcus)


Holds long head biceps in bicipital groove (between the tuberosities)


3.8.3.1. What happens if this is ruptured?


Indicate a moderate to severe shoulder separation, affects the stability


of AC joint, pain, range of movements will be impaired


Subluxed, dislocated or prolapsing long head of biceps





4. CLINICAL/SURFACE ANATOMY





4.1. Palpate and demonstrate on your willing and consenting peers the following:


4.1.1. Subcutaneous borders of the clavicle (concavity and convexity)

















4.1.1.1. Sternal end (with sternum & 1st costal cartilage forming sternoclavicular jt)








4.1.1.2. Acromial end(Flattened at the top; with Acromion forming acromioclavicular jt)

















4.1.2. Scapula:


4.1.2.1. Vertebral levels ( of medial end of Spine, Inf angle)


T2/3- T7





4.1.2.2. Acromion process





4.1.2.3. Apex of acromion ( lat. to and in front of acromial end of clavicle)


4.1.2.4. Acromial angle (change of direction of post inf. border of the acromion),


4.1.2.4.1. How is the length of the arm measured clinically?


Acromial angle to lateral condyle


4.1.3. Spine 4.1.4. Coracoid Process( just medial to humeral head and below the clavicle)





4.1.5. Humerus:


4.1.5.1. Greater tubercle


4.1.5.2. Lesser tubercle





4.1.6. Deltoid muscle


4.1.6.1. Posterior ( spinous ) fibres : Subject’s arm 90o abducted; apply resistance to the post and inferior aspect of arm. Feel the post bundle at the post aspect of shoulder


4.1.6.2. Anterior ( clavicular) fibres: Subject’s arm 90o abducted, elbow flexed. Ask the subject perform horizontal flexion of the shoulder which you resist to palpate the ant bundle





4.2. Study the following procedures and explain its anatomical basis:


4.2.1. Subacromial injection (ANM Upperlimb Dissection 54)





4.2.2. Locate the exact site of deltoid IM injection and explain why such a site


is chosen. (ANM Upperlimb Dissection 53)








4.3. Regarding the clavicle:


4.3.1. What is a fracture of a bone?


A fracture is a broken bone. It can range from a thin crack to a complete break.





4.3.2. Why and where is the most common site of clavicular fracture?


Between the middle (⅔) and the lateral third (⅓) of the clavicle because it’s the weakest part of clavicle (changing from convex to concave & changing in shape[circular and flattened])


Junction of medial ⅔ of shaft and lateral ⅓. A long bone fractures at its site of greatest change in curvature, change of cross section; supraclavicular nerves pierce





4.3.2.1. What structures are at risk with a fractured clavicle?


Brachial plexus trunks & divisions, subclavian vessels, supraclavicular nerves; skin


and associated chest injuries such as 'pneumothorax or hemothorax





4.3.2.2. Explain how the muscles attached to the clavicle are


displaced in the fracture








4.3.2.3. How will the patient present with a fractured clavicle and


explain why he assumes this characteristic posture?


Shoulder drops:The trapezius muscle is unable to hold the lateral fragment up owing to the weight of the upper limb; supporting sagging upper limb with opposite hand.


Prominent superiorly directed clavicle fragment(medial)[easily be palpated, and frequently seen]: Sternocleidomastoid muscle elevates the medial fragment of bone and clavicle is at subcutaneous position





A man supporting his sagging upper limb with his opposite hand- trapezius (by which the arm hangs) unable to support arm drawn medially by the adductors- teres major and pectoralis major





4.4 Regarding the scapula:


4.4.1. Explain the cause of Dropped shoulder and Winged scapula.





Position of scapula on posterior wall of thorax is maintained by tone and balance of the muscles attached to it. If one of these muscles is paralyzed, the balance is upset, as in dropping of the shoulder, which occurs with paralysis of the trapezius or winged scapula, caused by paralysis of the serratus anterior





Causes:


Loss of Serratus Anterior muscle function


The traumatic injury to the nerve supplying the serratus anterior muscle (the long thoracic nerve), or due to the pressure lesions or neuritis(inflammation of the nerve) which damage the nerve. The long thoracic nerve is vulnerable to injury than other nerves of the brachial plexus.


To test if it is the long thoracic nerve injury is by the serratus wall test; patient stand from the wall and then pushed against the wall with flat palms at waist level.











2. Loss of trapezius muscle function


It is may be the result of radical neck surgery (tumours) where the spinal accessory nerve which supplies the trapezius muscle is damaged.











3. Weakness of all scapula stabilisers


Muscular dystrophies (commonly known as FSHD FacioScapuloHumeral Dystrophy) are the culprit for weakness of all scapula stabilizing muscles











4. Loss of scapular suspensory mechanism


Since the acromioclavicular(AC) joint is the only joint that connects the scapula to the rest of the body. Thus, dislocation of the AC joint or the fracture of the outer third clavicle, with the rupture of coracoclavicular ligaments lead to an abnormal scapular rhythm





5. Winging of the scapula secondary to instability


Recurrent dislocations of the shoulder leads to dysfunction of the muscles that move and support the shoulder complex and scapula. The more dislocations, the worse the scapula dysrhythmia (winging).





6. Winging secondary to pain


Shoulder pain can cause abnormal movements of the entire shoulder complex. Therefore, reduced movements of the glenohumeral joint will lead to more compensatory movements by the scapula





7. Brachial Plexus injury or disease


Major accidents to the brachial plexus or Parsonage-Turner syndrome (Brachial neuritis) are causes to weakness of scapular muscles.


https://www.shoulderdoc.co.uk/section/492





4.5. Regarding bursa:
4.5.1. How is “painful arc syndrome” caused ?


Tear/ inflammatory degeneration or calcified deposit in supraspinatus tendon


Subacromial bursitis





Painful arc syndrome is also called supraspinatous tendonitis (inflamed tendon) mainly due to friction between supracromial tendon and acromion





Causation


bony structures such as subacromial spurs (bony projections from the acromion)


osteoarthritic spurs on the acromioclavicular joint


variations in the shape of the acromion


Thickening or calcification of the coracoacromial ligament can also cause impingement


Loss of function of the rotator cuff muscles, due to injury or loss of strength, may cause the humerus to move superiorly, resulting in impingement


Inflammation and subsequent thickening of the subacromial bursa (bursitis) may also cause impingement.


Weight training exercises where the arms are elevated above shoulder height but in an internally rotated position such as the upright row have been suggested as a cause of subacromial impingement.


-may also be due to subacromial bursitis


-may also be due to tendon tear or tendonitis because as abduction is conducted, the tendon impinge under the acromion


-usually in shoulder examination - angle of 60 - 120 degrees will induce the pain






4.5.2. Explain why pain occurs in mid-range of abduction.


Pain in mid range between 60 to 120 degrees of abduction


There is no pain in adduction because the inflamed bursa is away from the


acromion, but in abduction the supraspinatus tendon comes in contact with


the inferior surface of the acromion. Further the inflamed bursa slips


underneath the coracoacromial arch and gets impinged between the


supraspinatus and acromion.





4.6. Regarding shoulder joint:


4.6.1. What is the effect of prolonged immobilization of the joint?


Musculoskeletal complications include loss of muscle strength and


endurance, contractures and soft tissue changes, disuse osteoporosis, and degenerative joint disease.


The fibrous capsule tightens with inactivity and old age. The shoulder joint is vulnerable to immobilisation, particularly in the elderly and in diabetics, resulting in a ‘frozen shoulder’ (periarticular adhesions) with painful restriction of movement leading to further immobilisation (leading to even more fibrosis)





4.6.2. Define dislocation of a joint.


A joint dislocation, also called luxation, occurs when there is an


abnormal separation in the joint, where two or more bones meet. A partial dislocation is referred to as a subluxation





4.6.3. Which nerve(s) are commonly injury in relation to injuries of the shoulder joint?


Axillary nerve





4.6.3.1. How will you proceed to test such a nerve damage (clinical features)?


Inspection- squaring of the shoulder as the normal countour of the shoulder is lost


Sensory- regimental badge area


Motor- deltoid





4.6.4. Explain the anatomical basis of characteristic appearance of the dislocated shoulder joint on inspection.


Head of humerus held adducted by shoulder girdle muscles and internally rotated by subscapularis; loss of roundess of shoulder by downward displacement of greater tubercle








4.6.5. What is reduction of a dislocation?


Skilled manipulation to return bones to their normal position





4.6.5.1. Describe which movements of the humeral head is encouraged


(the anatomical basis) for reduction of the anterior dislocation of the


Shoulder


Each reduction method works by abduction and external rotation to


disengage the humeral head from the glenoid, with axial traction to


reduce it








4.6.5.2. How such principles of reduction is applied through the


Traction-countertraction method?


Traction-countertraction


The patient is placed supine (lie on the back) with the bed elevated. A


sheet is looped around the axilla with one free end on the chest and the


other underneath the back. The 2 ends should be of even length. An


assistant uses these free ends to apply countertraction. Then the


practitioner abducts the arm to 90 degrees and flexed the elbow to 90


degrees. With the forearm, slow longitudinal traction is then applied to


the affected extremity.