Shoulder anatomy and pathology

Question 1

What are the five main bony landmarks of the proximal humerus?

Answer 1

The proximal end of the Humerus consists of the articular head, greater tubercle (1), lesser tubercle (2), bicipital groove (3), anatomical neck and surgical neck of the humerus.

Question 2

What is the function of the greater tubercle?

Answer 2

The greater tubercle is covered by the deltoid and is what gives the shoulder it’s rounded shape. It has a posterior and superior aspect for muscle attachment of supraspinatus, infraspinatus and teres minor.

Question 3

What is the function of the lesser tubercle?

Answer 3

The lesser tubercle is immediately beyond the anatomical neck on the anterior surface. Subscapularis attaches here.

Question 4

What is the function of the bicipital groove?

Answer 4

The bicipital groove sits between the tubercles and is where the long head of biceps brachii runs.

Question 5

What is the function of the deltoid tuberosity?

Answer 5

The deltoid tuberosity is a rough area on the lateral side of the humeral shaft where the deltoid attaches.

Question 6

Describe the glenohumeral joint

Answer 6

The shoulder joint, also known as the Glenohumeral joint, is a ball and socket type synovial joint that permits a wide range of movement however that comes at the cost of instability. The round humeral head articulates with the shallow glenoid fossa of the scapula. This is deepened slightly by the ring like fibrous cartilaginous glenoid labrum.

Question 7

What is the function of the glenoid labrum?

Answer 7

Deepend the glenoid cavity slightly. The Glenoid labrum also acts as an anchoring point for ligaments.

Question 8

List the rotator cuff muscles

Answer 8

SITS = Supraspinatus, infraspinatus, Teres Minor and subscapularis.

Question 9

Describe the fibrous layer of the joint capsule

Answer 9

The loose fibrous layer of the joint capsule surrounds the glenohumeral joint and attaches medially to the margin of the glenoid cavity and laterally to the anatomical neck of the humerus. Superiorly the capsule encroaches on the root of the coracoid process so that the fibrous layer of the capsule encloses the proximal attachment of biceps brachii to the supra glenoid tubercle of the scapula within the joint.
The joint capsule has two openings. One between the tubercles of the humerus for passage of the long head of the biceps brachii and an open anterior and inferior to the coracoid process that allows communication between the subscapular bursa and the synovial cavity of the joint.
The inferior part of the joint is the only part not reinforced by the rotator cuff muscles and is its weakest part. It is lax when the arm is neutral and pulls taut when the arm is abducted

Question 10

Describe the fibrous layer of the joint capsule

Answer 10

The loose fibrous layer of the joint capsule surrounds the glenohumeral joint and attaches medially to the margin of the glenoid cavity and laterally to the anatomical neck of the humerus. Superiorly the capsule encroaches on the root of the coracoid process so that the fibrous layer of the capsule encloses the proximal attachment of biceps brachii to the supra glenoid tubercle of the scapula within the joint.
The joint capsule has two openings. One between the tubercles of the humerus for passage of the long head of the biceps brachii and an open anterior and inferior to the coracoid process that allows communication between the subscapular bursa and the synovial cavity of the joint.
The inferior part of the joint is the only part not reinforced by the rotator cuff muscles and is its weakest part. It is lax when the arm is neutral and pulls taut when the arm is abducted

Question 11

What are the intrinsic ligaments of the shoulder?

Answer 11

The glenohumeral ligaments (which strengthen the anterior aspect of the joint capsule) and the coracohumeral ligaments, which strengthen the capsule superiorly are intrinsic ligaments. I.E. they are a part of the fibrous capsule.

Question 12

Describe the glenohumeral ligaments

Answer 12

The glenohumeral ligaments are three fibrous bands that radiate lateraly and inferiorly from the glenoid labrum at the supraglenoid tubercle and blend distally with the fibrous layer of the capsule at the anatomical neck of humerus.
Superior glenohumeral ligament attaches at a depression above lesser tubercle.
Middle glenohumeral ligament attaches at the lower part of lesser tubercle.
Lower glenohumeral ligament attaches at lower part of anatomical neck.

Question 13

Describe the coracohumeral ligament

Answer 13

The coracohumeral ligament is a strong broad band that passes from the base of the coracoid process to the anterior aspects of the greater tubercle of the humerus.

Question 14

Describe the transverse humeral ligament

Answer 14

The transverse humeral ligament is a broad fibrous band the bridges over the intertubercular sulcus converting the groove into a canal that hold the synovial sheath and the long head of biceps brachii in place during movements of the joint.

Question 15

Describe the coracoacromial arch

Answer 15

The coracoacromioarch is an extrinsic protective structure. It is formed by the smooth inferior aspect of the acromion and coracoid process with the coraco acromial ligament spanning between them. This overlies the humeral head preventing superior displacement. It is so strong that the clavicle or humerus will fracture before the arch breaks.

Question 16

Describe the subacromial bursa

Answer 16

The subacromial bursa is sometimes referred to as the sub deltoid bursa and is located between the acromion, coraco-acromio ligament and deltoid superiorly and the supraspinatus tendon and joint capsule of the glenohumeral joint inferiorly. As such it facilitates movement of the supraspinatus tendon under the coraco-acromial arch and of the deltoid over the joint capsule of the GH Joint and greater tubercle of the humerus. It does not normally communicate with the joint capsule.

Question 17

Describe the sub scapular bursa

Answer 17

The subscapular bursa is located between the tendon of subscapularis and the neck of the scapula. It protects the tendon where it passes over the inferior root of the coracoid process and over the neck of the scapula. It usually communicates with the cavity of the Glenohumeral joint through an opening in the fibrous layer of the capsule.

Question 18

What is the location and function of the supraspinatus muscle?

Answer 18

Origin - Supraspinatus fossa. Insertion - Greater tubercle Aids deltoid in abduction. Resists downward slippage of the humerus. Supports GH capsule superiorly.

Question 19

What is the location and function of the infraspinatus muscle?

Answer 19

Origin - Infraspinus fossa. Insertion - Greater Tubercle Action - Lateral rotations. Prevents humeral head from slipping upward. Modulates deltoid action. Supports GH capsule posteriorly.

Question 20

What is the location and function of the teres minor muscle?

Answer 20

Origin - Lateral border and adjacent posterior surface of scapula. Insertion - Greater tubercle. Posterior surface of joint capsule. Action - Lateral rotations. Prevents humeral head from slipping upward. Modulates deltoid action. Supports GH capsule posteriorly. Some books say it aids in adduction.

Question 21

What is the location and function of the subscapularis muscle?

Answer 21

Origin - Subscapular fossa. Insertion - Lesser tubercle. Action - Anterior surface of joint capsule. Medial rotation. Contracts during most active movements of the GH joint to stabilise it. Strengthens the GH capsule anteriorly.

Question 22

What is the location and function of the subscapularis muscle?

Answer 22

Origin - Subscapular fossa. Insertion - Lesser tubercle. Action - Anterior surface of joint capsule. Medial rotation. Contracts during most active movements of the GH joint to stabilise it. Strengthens the GH capsule anteriorly.

Question 23

What is the location and function of the biceps brachii long head muscle?

Answer 23

Origin - Superior glenoid tubercle. Insertion - tuberosity of radius and fascia of forearm via bicipital aponeurosis Action - Most important stabiliser in the shoulder. Holds the humeral head against the glenoid cavity.

Question 24

What is the location and function of the biceps brachii short head muscle?

Answer 24

Origin - Corcaoid process. Insertion - tuberosity of radius and fascia of forearm via bicipital aponeurosis Resists dislocation of the shoulder.

Question 25

What is the location and function of the triceps brachii long head muscle?

Answer 25

Origin - Infraglenoid tubercle. Inserti0n - Proximal end of olecranon. Action - Resists dislocation of the humerus, especially important during adduction. Supports GH inferiorly.

Question 26

What is the location and function of the coracobrachialis muscle?

Answer 26

Origin - Coracoid process. Insertion - Middle third of medial humerus. Action - Help flex and adduct the arm. Resists dislocation of the shoulder.

Question 27

What is the location and function of the coracobrachialis muscle?

Answer 27

Origin - Coracoid process. Insertion - Middle third of medial humerus. Action - Help flex and adduct the arm. Resists dislocation of the shoulder.

Question 28

How is it possible for the shoulder to have 180 degrees of movement?

Answer 28

Together the Glenohumeral (GH), Acromioclavicular (AC) and Scapulothoracic (ST) joints work together to produce a greater range of motion that is possible at any one joint achieving approximately 180 degrees in any direction.

Question 29

Describe scapulohumeral rhythm

Answer 29

For each two degrees of GH flexion or abduction there is one degree of upward rotation of the ST joint. Thus, the GH joint contributes 120 degrees of flexion or abduction and the ST contributes 60 degrees of upward scapula rotation which yields a total of 180 degrees arm trunk elevation.
The 15-20 degrees of movement at the AC joint is what permits positioning of the glenoid cavity that is necessary for arm movements.

Question 30

Comment on stability versus mobility

Answer 30

The mobility of the shoulder joint comes at the cost of stability and so requires extensive soft tissue support.
Whilst the joint ligaments limit the range of movement passively – they have a limited length and do not stretch – the rotator cuff muscles provide dynamic stability by contracting and pushing the ball and socket together.
The tendons of the rotator cuff muscles also fuse into the joint capsule on all sides except inferiorly thereby helping to strengthen and stabilize the joint.
As the inferior part of the joint is less supported it is more prone to dislocation.

Question 31

What are the three main bursa of the shoulder?

Answer 31

Subdeltoid/subacromial, subcoracoid, subscapaular.

Question 32

Comment on the function of the subacromial bursa

Answer 32

The subacromial bursa is sometimes referred to as the sub deltoid bursa and is located between the acromion, coraco-acromio ligament and deltoid superiorly and the supraspinatus tendon and joint capsule of the glenohumeral joint inferiorly. As such it facilitates movement of the supraspinatus tendon under the coraco-acromial arch and of the deltoid over the joint capsule of the GH Joint and greater tubercle of the humerus. It does not normally communicate with the joint capsule.

Question 33

Comment on the function of the subscapular bursa

Answer 33

The subscapular bursa is located between the tendon of subscapularis and the neck of the scapula. It protects the tendon where it passes over the inferior root of the coracoid process and over the neck of the scapula. It usually communicates with the cavity of the Glenohumeral joint through an opening in the fibrous layer of the capsule.

Question 34

Comment on the function of the subcoracoid bursa

Answer 34

The subcoracoid bursa is located anterior to subscapularis and beneath the coracoid process and extends caudal to the conjoined tendons of coracobrachialis and short head of biceps brachii. Fluid in the subcoracoid bursa does not normally communicate with the glenohumeral joint but may communicate with the subacromial bursa.

Question 35

List the common symptoms of shoulder pathology

Answer 35

• an arc of shoulder pain when the arm is at shoulder height or positioned overhead
• pain that extends from the top of shoulder to elbow
• pain when lying on the sore shoulder
• muscle weakness or pain when attempting to lift or reach.
• pain when putting your hand behind your back or head

Question 36

Describe tendonitis

Answer 36

Tendonitis is an accurate diagnosis of an acute injury when the tendon is overloaded, causing pain and swelling from tears in the injured tissue. It is usually painful and a generic term that has to do with overuse, irritation, strain, degeneration and poor mechanics.

Question 37

Describe tendonosis

Answer 37

Tendonosis occurs from failed healing or repetitive trauma to a tendon. This chronic microtrauma leads to loss of collagen continuity which means the fibers are no longer aligned and fail to link together, resulting in loss of strength and further injury when used. However, inflammation is not generally present with tendonosis. Collagen is degenerated and disorganized and has increased vascularity and cellularity without obvious inflammatory cells.

Question 38

Describe tendinopathy

Answer 38

Tendinopathy literally means a disease or disorder of a tendon. Tendinopathy is typically used to describe any problem involving a tendon. A tendinopathy is an overuse condition that manifests itself as pain in and around tendons and happens when the body fails to regenerate properly. This painful condition is associated with tendon disorganization and thickening that reduces its physical properties, which causes the tendon to fatigue, further exacerbating the painful condition with ultimate failure

Question 39

What symptoms to patients who have a partial or complete rotator cuff tear present with?

Answer 39

Patients commonly present with reduced shoulder function and may have pain at rest, night pain and painful arc. The clinician may find weak external rotators, a weak supraspinatus, and signs of impingement.
Signs of impingement may include painful overhead reaching, an inflamed subdeltoid bursa, or positive special tests meant to provoke symptom.

Question 40

What is the common demographic for patients who have a partial or complete rotator cuff tear present with?

Answer 40

Patients over the age of 60 with two out of three of the aforementioned symptoms (i.e. weak external rotators, weak supraspinatus, impingement signs previously listed), there is a 98% chance of a RC tear.

Question 41

What sort of abduction pain will patients with impingement syndrome present with?

Answer 41

If there is shoulder impingement a patient will have pain abducting their arm to the horizontal. It will not be as painful at the beginning of the movement nor will it be as painful when moved next to the head

Question 42

What are the most common causes of shoulder impingement?

Answer 42

The most common causes of shoulder impingement are arthritis of the acromion (“hooking” of the acromion ) or weakness of the rotator cuff muscles.

Question 43

How do weak rotator cuff muscles result in shoulder impingement?

Answer 43

The rotator cuff muscles help keep the head of the humerus applied tightly to the glenoid fossa through any range of shoulder movement. If these muscles weaken the movements of abduction and flexion result in the head of the humerus riding up to the glenoid cavity, causing the supraspinatus tendon to rub against the acromion.

Question 44

Describe shoulder impingement process

Answer 44

With shoulder impingement, the space between the acromion and the head of the humerus is narrowed so that the tendon of the supraspinatus muscle rubs against the underside of the acromion. This produces pain and can lead to a tearing of the tendon.

Question 45

What is the most common cause of shoulder pain?

Answer 45

It is currently thought that between 44‐64% of all shoulder pain is from subacromial impingement syndrome (SAIS),

Question 46

What are some causes of SAIS

Answer 46

This can be caused by acromial shape, subacromial joint spurs, and AC joint spurs as well as rotator cuff muscle weakness.

Question 47

What symptoms to patients with Supraspinatus tendinitis present with and why?

Answer 47

It can present with pain on palpation at the insertion point (greater tubercle). Pain against resistance for the first 35 degrees (as supraspinatus intiates abduction), Pain between 70-120 degrees on free movement (as the supraspinatus tendon is compressed between the greater tubercle and the acromion) and sometimes pain that shoots down the arm (due to referred pain from the suprascapular nerve)

Question 48

What are some common causes of supraspinatus tendinitis?

Answer 48

Supraspinatus tendinitis can be from an overuse injury. Common in athletes and workers with repetitive motion of arm abduction.

Question 49

Describe symptoms, cause of symptoms and demographic of calicific tendonitis

Answer 49

Deposition of calcium in the supraspinatus tendon is common. It causes increased local pressure around the deposit that usually leads to excruciating pain during abduction of the arm. It may radiate down to the hand. The calcium deposit may irritate the overlying subacromial bursa leading to subacromial bursitis.
As long as the GH joint is adducted there is no pain as the painful lesion is away from the inferior surface of the acromion. Usually it will cause pain between 50-130 degrees of abduction (painful arc syndrome) because during this arc the supraspinatus tendon is in close contact with the inferior surface of the acromion.
It is most common in males over 50 after unusual or excessive use of the GH joint.

Question 50

Describe the symptoms and cause of symptoms of subacromial bursitis

Answer 50

Subacromial bursitis can be an overuse injury. Pain will be worse at the initial stages of abduction or when carrying a heavy object and there will be point tenderness. The supraspinatus muscle tendon is separated from the coracoacromial ligament, the acromion, and the deltoid muscle by the subacromial bursa. When this bursa is inflamed, abduction of the arm will be painful.
Supraspinatus and deltoid muscles move the arm to about 90° from the side of the body. No further abduction is produced at the shoulder joint as the remaining abduction above the head is achieved through scapular rotation. Thus, the pain is felt only during the initial stages of abduction i.e. thru glenohumeral movements

Question 51

Explain why calcification may occur with injury

Answer 51

As part of the aging process, blood flow to the tendons of the rotator cuff decreases. This makes the tendon weaker. Due to the wear and tear as we use our shoulder, the fibres of the tendons begin to fray and tear, just like a worn-out rope. Calcium deposits form in the damaged tendons as a part of the healing process.
Usually, the tendon heals via the action of collagen forming cells known as fibroblasts. After weeks or months, the fibroblasts became less numerous in the region and replaced by osteoblasts (bone-forming cells). These osteoblasts stimulate the growth of bone (calcium) in the tendon.
Hence the main reason for the development of calcific tendonitis appears to be delayed healing