The Shoulder Joint Flashcards
Describe the shoulder joint
Shoulder Joint (Gleno humeral joint) Synovial joint Ball & socket type Most mobile joint: Wide range of movements in multiple planes Least stable: most commonly dislocated
What are he articular surfaces of the shoulder joint
Glenoid fossa - in the living state the glenohumeral fossa would be covered with articular cartilage
and head of humerus - also covered with articular cartilage
There is a 4:1 disproportion in area of articular surfaces (had bigger) - glenoid cavity deepened by glenoid fossa
Why is the glenohumeral joint unstable?
SJ inherently unstable – Glenoid fossa shallow – Disproportion of articular surfaces – Multiplanar movements – Lax capsule
How is the glenohumeral joint made more stable?
Stability is achieved by – Muscles of the rotator cuff (most important) – Other muscles – Ligaments – Capsule
Describe the capsule
Capsule Attached to – Glenoid labrum & margins of glenoid fossa – anatomical neck of humerus – dips down medially to surgical neck (laxity for full abduction) – bridges intertubular groove Tough but lax to allow movement Small opening anteriorly – synovial membrane of SJ communicates with subscapular bursa
What is the role of synovial membrane?
Synovial Membrane
Lines:
1. Capsule
2. Intra capsular bone, up to edge of articular cartilage
3. Tendon of long head of the biceps within joint cavity
The tendon acquires a tubular sleeve of synovium as it enters joint, which surrounds it up to its insertion
What are the intra capsular ligaments
Intra capsular Ligaments
• 3 Gleno-humeral ligaments (superior, middle, inferior)
• 3 fibrous bands
• extend from glenoid labrum to humerus
• Part of the fibrous capsule
• Reinforces capsule anteriorly
• Can only be seen from inside the capsule
What are the extracapsular ligaments?
- Coracoacromial ligament (CAL)
Between Acromion & coracoid process (important – more later) - Coracohumeral ligament
From base of coracoid process to anterior part of greater tubercle - Transverse humeral ligament
holds the tendon of long head of biceps in place during shoulder movement)
What is the coraco acromial arch?
Formed by Coracoacromial ligament + Acromion + Coracoid process
– a strong structure of bone & ligament (osseoligamentous structure )
– overlies the humeral head;
– prevents upper displacement of humerus
– Clinically important in the `painful arc’ syndrome (more later)
What is the rotator cuff
A collective name given to 4 short muscles closely associated with the joint The most important factor giving stability to the joint 1. Supraspinatus, 2. Infraspinatus, 3. Teres minor 4. Subscapularis mnemonic = ‘sits’
Where to the rotator cuff muscles arise and insert?
3 arise on dorsal aspect of Scapula
Supraspinatus
Infraspinatus
Teres minor
All 3 muscles inserted into Greater tubercle of humerus
Supraspinatus tendon passes under Coraco-acromial arch
Teres minor arises from ?? Inserts at?
1 from ventral aspect of Scapula
Subscapularis
Subscapularis muscle inserted into lesser tubercle
What is the role of the rotator cuff muscles?
Rotator Cuff Muscles
• The tendons blend to form a cuff
• Cuff fuses with capsule and strengthens it
• Tone in the muscles holds the head close to glenoid cavity
• Supraspinatus tendon is separated from Coraco acromial arch (CAA) by the bursa.
What are the actions of the rotator cuff muscles?
ACT to stabilise the Shoulder joint, holding the head of the humerus in the glenoid cavity.
Also:
Supraspinatus – initiation & first 150 of abduction.
n – suprascapular C5,6
Infraspinatus – lateral (external) rotation of the arm
n – suprascapular C5,6
Teres Minor – lateral rotation of the arm weak adductor
n – axillary C5,6
Subscapularis - medial (internal) rotation of the arm
n – upper & lower subscapular nerves C5,6
What other muscles stabilise the shoulder joint?
Other muscles stabilising SJ 1. Deltoid 2. Long head of biceps (attached to Supra glenoid tubercle) 3. Long head of triceps (attached to Infra glenoid tubercle)
What is the static and dynamics stability of the shoulder joint provided by?
- Tendons of the rotator cuff (Dynamic) (anteriorly, posteriorly, superiorly)
- Coraco acromial arch (superiorly)
- Gleno -humeral (Intra capsular) ligaments (anteriorly, inferiorly) 4. Coraco-humeral ligament (superiorly)
- Deepening glenoid cavity by labrum (circumferentially) 6. Splinting effect of: the long head of the biceps (Dynamic) (superiorly) & the long head of the triceps (Dynamic) (inferiorly)
- Other muscles (Dynamic) – Deltoid (anteriorly, posteriorly, superiorly) Pectoralis major (anteriorly), Coracobrachialis (anteriorly)
What is the subacromial bursa?
Facilitates movement of supraspinatus tendon under the Coraco acromial arch & Deltoid
What is the subscapular bursa?
- Facilitates movement of subscapularis tendon over scapula
* communicates with the joint cavity
What is in the space between the acrimony and head of the humerus
Space between acromion & head of humerus about 1- 1.5cm
Interposed in this space are the:
1. Subacromial Bursa
2. Supraspinatus tendon
3. Capsule
4. Tendon of Long head of Biceps
During abduction, risk of soft tissue impingement between Head of humerus & Acromion
Describe the blood supply to the shoulder joint
- Anterior circumflex humeral artery
- posterior circumflex humeral artery
- Suprascapular artery
Describe the nerve supply to the shoulder joint
Nerve supply:
•Axillary nerve
•Suprascapular
•Lateral Pectoral nerves from the brachial plexus (C5,6);
Where do the movements of the shoulder joint occur?
Occur at Glenohumeral joint & Scapulothoracic joint. (Scapula moves over thorax as if there was a joint)
Describe the abduction of the shoulder joint
First 900 abduction - Glenohumeral joint
• 00 – 150 Supraspinatus - suprascapular nerve
• 15- 900 Deltoid (central fibres) – axillary nerve
Above 900 By rotation of scapula at Scapulothoracic joint
Trapezius (upper fibres) & Serratus anterior
What is the role of the trapezius
Trapezius – n Accessory nerve
• Superior fibres of trapezius rotate scapula upwards on chest wall
Attached to spinous processes and nuchal ligament
What is the role of the serrated anterior?
Serratus anterior n - long thoracic nerve
• protracts and stabilises scapula
on chest wall;
• assists in upward rotation
What extends the shoulder joint?
Extension of the shoulder joint
• Posterior fibres of Deltoid
n-Axillary nerve
• Latissimus dorsi
n-thoraco dorsal nerve
• Teres major
n- Lower subscapular
What flexes the shoulder joint?
Flexion of the shoulder joint
- Clavicular head of Pectoralis major – (medial & lateral pectoral nerves)
- Anterior fibres of Deltoid – (axillary nerve)
- Coracobrachialis - (musculocutaneous nerve)
- Biceps brachii - (musculocutaneous nerve)
What adducts the shoulder joint?
Adduction of the shoulder joint
• Pectoralis major (medial & lateral pectoral nerves)
• Latissimus dorsi (long thoracic nerve)
• Teres major (lower subscapular)
What internally rotates the shoulder joint?
Internal (Medial) rotation
- Sternal head of pectoralis major (n –Medial & Lateral Pectoral nerves)
- Subscapularis (n- upper and lower subscapular nerves)
- Teres major (n - lower subscapular)
- Latissimus dorsi (n – Thoraco dorsal)
What externally rotates the shoulder joint?
Lateral (external) rotation
• Infraspinatus (n – suprascapular) • Teres minor (n-axillary)
