The Shoulder joint Flashcards
What joints are involved in movement of the shoulder?
- Glenohumeral
- Scapulothoracic
What is the articulating surface of the SJ?
-Between the head of humerus and the glenoid cavity of the scapula
What lines the articulating surface of the GHJ?
-Hyaline articular cartilage
What is the glenoid labrum?
-A fibrocartilaginous rim which deepens the glenoid cavity and increases the area of articulation
What is the cost of the shoulder joint being extremely mobile?
-It is the least stable joint
What makes the shoulder joint unstable?
- Sits shallowly in glenoid cavity
- Disproportionate articular surfaces
- Multiplanar movement
How is stability of the SJ achieved?
- Rotator Cuff muscles
- Ligaments
- Capsule
- Other muscles
What type of joint is the glenohumeral joint?
-Synovial ball and socket joint
What is the anatomical location of the capsule?
- Extends from glenoid labrum and glenoid cavity margins to anatomical neck of humerus
- Bridges the intertubecular groove
- Dips medially to the surgical neck
There is a small anterior gap in the capsule, what does this allow?
-Continuation of synovial membrane into subscapular bursa
What lines the fibrous capsule?
-Synovial membrane
Within the joint cavity, what does the synovial membrane line?
- Capsule
- Bone upto articulating cartilage
- Tubular sleeve around tendon of biceps
What is the function of the capsule of the SJ?
-Provide support as it is tough but lax to allow movement
Describe the intracapsular ligaments
-Fibrous bands which lay within the capsule and extend from the glenoid labrum to the humurus
Name the intracapsular ligaments
-Superior, middle and inferior gleno-humeral ligaments
Where, anatomically, do the intracapsular ligament provide support?
- Anteriorly
- Inferiorly
Name the extracapsular ligaments of the SJ
- Coracoacromial ligament (CAL)
- Coraco-humeral ligament (CHL)
- Coracoclavicular ligament (CCL)
- Transverse humeral ligament (THL)
Where is the coracoacromial ligament?
-Between the acromion and the coracoid process
What is the function of the transverse humeral ligament?
-Holds tendon of long head of biceps in place during movement
Where anatomically do the extracapsular ligaments provide support?
-Superiorly
What is the function of the coracoacromial arch?
-A strong structure which overlies the humeral head and prevents upper displacement of the humerus
Besides the rotator cuff, which other muscle support the SJ?
- Deltoid
- Long head of biceps and triceps
What structures lie inbetween the acromion and the humeral head? Why is this significant?
-Subacromial busa
-Rotator Cuff tendons
-Fibrous capsule
(Synovial membrane)
-Tendon of long head of biceps
-Synovial membrane
Any of these structures are at risk of impingement on aBduction
What are bursae?
-Small sacs filled with synovial fluid and lined with synovial membrane
What is the function of bursa?
-Facilitates movements of structures upon one another by reducing friction
What are the two main bursae in the SJ?
- Subscapular bursa
- Subacromial bursa
What is the function of the subscapular bursa?
-Facilitate movement of subscapularis tendon over scapula
What is the function of the subacromial bursa?
-Facilitate movement of supraspinatus tendon under CAA and deltoid over the SJ capsule/humerus
What muscles are responsible for flexion of the arm?
- Coracobrachialis
- Biceps brachii
- Pectoralis major
- Anterior deltoid fibres
What muscles are responsible for extension of the arm?
- Latissimus dorsi
- Teres major
- Posterior deltoid
What muscles are responsible for aBduction of the arm?
- Supraspinatus (0-15)
- Deltoid (15-90)
- Trapezius and serratus anterior (above 90)
What muscles are responsible for ADduction?
- Lat Dorsi
- Teres major
- Pec major
What muscles are responsible for medial rotation?
- Lat dorsi
- Teres major
- Subscapularis
- Pec major
What muscles are responsible for lateral rotation?
- Infraspinatus
- Teres minor
What nerves supply the shoulder joint?
- Suprascapular
- Axillary
- Subscapular
- Lateral pectoral
What arteries supply the shoulder joint?
- Anterior and posterior humeral cicumflex from axillary
- Suprascapular from right subclavian
How is the axillary nerve vulnerable to injury around the shoulder joint?
- Between deltoid and humerus in intramuscular injections
- In the space just below shoulder joint and just above teres major, from anterior dislocations
- During fractures of the surgical neck of humerus
What is the consequence of axillary nerve injury?
- Loss of sensation over regimetals badge
- Paralysis of deltoid
- Loss of ABduction
In which direction does the shoulder joint usually dislocate?
-Anterior, inferiorly (due to this being the least supported area)
How does an anterior dislocation of the shoulder joint usually occur?
-Trauma to the arm when it is fully abducted
What is the consequence of capsule or rotator cuff tear accompanying a shoulder dislocation?
-Poor healing with increased chance of recurrent dislocation
What is painful arc syndrome?
-Pain on abduction of the arm between 50 and 130degrees caused by supraspinatus rubbing under the coracoacromial arch or impingement
Which bursa is likely to become inflamed in painful arc syndrome?
-Subacromial bursa
Which tendon can become inflamed in painful arc syndrome and what is this called?
- Supraspinatus tendon
- Supraspinatus tendonitis
What are the predisposing factors to painful arc syndrome?
- Repetitive overuse eg racquet sports, occupation with arms overhead
- Age -> degeneration of tendons
- Avascularity of supraspinatus tendon
