Shoulder Region, Shoulder Joint, Arm and Cubital Fossa Flashcards
[6-minute video]: cadaveric demonstration of the Shoulder Joint
[11-minute video]: cadaveric demonstration of the Shoulder Joint
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Here are some MRI images of the upper limb. Click on Answer to view them.
Discuss Erb’s paralysis. Hint: (1) Nerve roots involved, (2) 9 muscles that are paralyzed, (3) describe the position of upper limb and hand, (4) sensory loss, (5) autonomic signs
(1) Nerve roots involved: C5 and C6
(2) Muscles paralyzed: Deltoid, supraspinatus, infraspinatus, biceps brachii, brachialis, brachioradialis, supinator and extensor carpi radialis longus
(3) Position of upper limb and hand:
Policeman’s tip [aka. Waiter’s tip], characterized by
☯︎ arm adduction
☯︎ medial rotation
☯︎ elbow extension
☯︎ pronation
(4) Sensory loss: along outer aspect of arm
(5) Autonomic signs: absent
List the 6 neural structures that meet at Erb’s point.
☛ C5 nerve root
☛ C6 nerve root
☛ nerve to subclavius
☛ suprascapular nerve
☛ anterior division of the upper trunk
☛ posterior division of the upper trunk
[Diagram]
Discuss Klumpke’s paralysis. Hint: (1) Nerve roots involved, (2) 9 muscles that are paralyzed, (3) describe the position of upper limb and hand, (4) sensory loss, (5) autonomic signs
(a) Nerve roots involved: C8 and T1
(b) Muscles paralyzed: all intrinsic hand muscles as well as some muscles of the forearm
(c) Position of hand: claw hand [Diagram]
☯︎ paralysis of flexors of wrist and fingers
☯︎ paralysis of intrinsic hand muscles
(d) Sensory loss: along medial border of forearm and hand
(d) Autonomic signs: present (Horner’s syndrome)
[Diagram 1] [Diagram 2]
Outline the surface landmarks of the shoulder region.
Clavicle
Suprasternal notch (jugular notch)
Sternal angle (of Louis)- useful landmark to identify 2nd rib
Infraclavicular fossa (palpate on yourself)
Coracoid process
Nipple
Describe the sensory innervation of the shoulder region.
Upper half of the deltoid region is supplied by the supraclavicular nerves (C3, C4)
Lower half of the deltoid region is supplied by the superior lateral brachial cutaneous nerve (C5-C6), which is a cutaneous branch of the axillary nerve.
[Diagram]
What joints constitute the shoulder joint complex?
- Glenohumeral joint
- Acromioclavicular joint
- Sternoclavicular joint
- Scapulothoracic articulation/scapulothoracic linkage (functional linkage between the scapula and thorax)
What type of joint is the glenohumeral joint?
(Brief note: This joint is the primary articulation of the shoulder girdle and generally termed shoulder joint by clinicians.)
Ball-and-socket type of synovial joint
Attachments of capsule of glenohumeral joint?
Medially: margins of the glenoid cavity beyond the glenoid labrum but it extends beyond the supraglenoid tubercle thus enclosing the long head of biceps brachii
Laterally: anatomical neck of humerus
Inferiorly: extends downwards 1.5 cm or more on the surgical neck of the humerus
[Diagram]
Differentiate between Erb’s paralysis and Klumpke’s paralysis in terms of mode of injury.
Erb’s paralysis is caused by excessive increase in the angle between the neck and the shoulder (e.g. falling and landing on the shoulder, or traction of the arm during birth) whereas Klumpke’s paralysis is caused by hyperabduction of the arm (which may occur when one falls on an outstretched hand or an arm is pulled into machinery or during delivery).
[Diagram]
List crucial ligaments of the glenohumeral joint and accessory ligaments of the joint as well.
Crucial ligaments:
1. Capsular ligament
2. Superior, middle and inferior glenohumeral ligaments
3. Coracohumeral ligament (from the base of the coracoid process to the anterior aspect of the greater tubercle of the humerus)
4. Transverse humeral ligament (this bridges the bicipital groove between the greater and lesser tubercle, converting the groove into a canal that provides passage to the tendon of long head of biceps brachii surrounded by a synovial sheath)
Accessory ligaments
1. Coracoacromial ligament - protects superior aspect of the joint
2. [Technically not a ligament, but just take note …] Coracoacromial arch formed by coracoid process, acromion process and coracoacromial ligament between them, forming a protective arch for the head of humerus and preventing its superior dislocation above the glenoid cavity
[Note: supraspinatus muscle passes under this arch and lies deep to the deltoid where its tendon blends with the joint capsule]
List bursae related to the shoulder joint.
- Subscapular bursa - lies between tendon of subscapularis and the neck of scapula and protects the tendon from friction against the neck of scapula
- Subacromial bursa - lies between the coracoacromial arch and supraspinatus tendon and joint capsule. It continues downwards beneath the deltoid, where it is referred to as the subdeltoid bursa.
- Infraspinatus bursa - lies between the tendon of infraspinatus and posterolateral aspect of the joint capsule.
- [Diagram 1] [Diagram 2]
What other stability factors are there besides what has been mentioned in the glenohumeral joint so far (the ligaments)? Briefly explain how they contribute to stability.
- Rotator cuff (musculotendinous cuff) muscles - their medial pull holds the head of the humerus against the smaller and shallow glenoid cavity
- Long head of biceps tendon - passes above the head of the humerus thus prevents its upwards dislocation
- Glenoid labrum - deepens shallow glenoid cavity
- Coracoacromial arch - forms the secondary socket of the glenohumeral joint and prevents upward dislocation of the head of the humerus
Movements of the glenohumeral joint? (State the movement, its prime movers and its accessory muscles. There are 6 key movements.)
- Flexion: Pectoralis major (clavicular part), deltoid (anterior fibres), short head of biceps brachii, coracobrachialis, pectoralis major (sternocostal head)
- Extension: Deltoid (posterior fibres), latissimus dorsi, teres major, long head of triceps
- Adduction: pectoralis major (sternocostal part), latissimus dorsi, teres major, coracobrachialis, short head of triceps, long head of triceps
- Abduction: deltoid (lateral fibres) (15 to 90 degrees), supraspinatus (initiator from 0 to 15 degrees), serratus anterior, upper and lower fibres of trapezius
- Medial rotation: subscapularis, pectoralis major, latissimus dorsi, deltoid (anterior fibres), teres major
- Lateral rotation: deltoid (posterior fibres), infraspinatus, teres minor
Bold indicates prime movers.
Describe the mechanism of arm abduction.
The total range of abduction is 180°. Abduction up to 90° occurs at the glenohumeral joint. Abduction from 90° to 120° can occur only if the humerus is rotated laterally.
Abduction from 120° to 180° can occur if the scapula rotates forwards on the chest wall.
The articular surface of the head of humerus permits elevation of arm only up to 90°, because when the upper end of humerus is elevated, to 90° its greater tubercle impinges upon the under surface of the acromion and can only be released by lateral rotation of the arm.
Therefore, the arm rotates laterally and carries abduction up to 120°.
Abduction above 120° can occur only if scapula rotates.
So that the scapula rotates forwards on the chest wall.
Give the range of motions of the various arm movements.
☯︎ Flexion: 90°
☯︎ Extension: 45°
☯︎ Abduction: 180°
☯︎ Adduction: 45°
☯︎ Lateral rotation: 45°
☯︎ Medial rotation: 55°
Why does dislocation of the shoulder joint mostly occur inferiorly?
Because the joint is least supported on this aspect. “There is no cuff inferiorly.” (from Last’s)
Which nerve is often injured during dislocation of the shoulder joint?
The axillary nerve because of its close relation to the inferior part of the joint capsule.
Clinically, dislocation of the shoulder joint is described as anterior or posterior dislocation indicating what?
Indicating whether the humeral head has descended anterior or posterior or to the infraglenoid tubercle of the scapula and long head of the triceps.
What usually causes dislocation at the shoulder joint?
excessive extension and lateral rotation of the humerus
How does dislocation of the shoulder joint clinically present itself?
(a) Hollow in rounded contour of the shoulder
(b) Prominence of shoulder tip
(c) [Diagram]
Discuss frozen shoulder (adhesive capsulitis). (Hint: Symptoms, cause)
It is a clinical condition characterized by pain and uniform limitation of all movements of the shoulder joint, though there are no radiological changes in the joint. It occurs due to shrinkage of the joint capsule, hence the name adhesive capsulitis. This condition is generally seen in individuals with 40–60 years of age.
Name two rotator cuff disorders.
- calcific supraspinatus tendinitis [caused by deposition of calcium phosphate in the tendon of supraspinatus. Calcium deposition irritates the overlying subacromial bursa causing subacromial bursitis. Consequently, when the arm is abducted the inflamed bursa is caught between the tendon and coracoacromial arch, and this causes severe pain.]
- subacromial impingement syndome