3.3 Shoulder complex Flashcards
What are the joints of the shoulder?
3 true bi-articular synovial joints
- sternoclavicular
- acromioclavicular
- glenohumeral
2 physiological/functional joints
- subdeltoid
- scapulothoracic
Ligaments for joint stability
Muscles
Nerves, blood supply (Hilton’s Law: the blood and n’ supply near a joint will supply that joint)
What movements is the shoulder complex capable of?
F/E
Adduction/abduction
medial rotation/lateral rotation
circumduction
Sternoclavicular (SC) joint
- Connects upper limb with thorax
- Saddle joint (like thumb)
- Articular disc (complete articular disc divides into 2 separate compartments that allow separate movements)
- 3 ligaments (sternoclavicular, interclavicular, costoclavicular)
- dislocation uncommon
- blood supply (internal thoracic, suprascapular)
- nerve supply (N. to subclavius)
- movements: elevation/depression, protraction/retraction, circumduction
What causes sternoclavicular subluxation?
Usually direct trauma to front of chest.
The vessels at the root of the neck are susceptible to injury
Anterior subluxation of clavicle - fixed by immobilising joint
Posterior - much more dangerous, brachial plexus & subclavian artery travel behind
What are the features of the acromioclavicular (AC) joint?
- Connects acromial end of clavicle with scapula
- Plane joint
- Partial articular disc
- Intrinsic ligament: acromioclavicular ligament
- Extrinsic ligament: coracoclavicular ligament (conoid, trapezoid)
- Shoulder separation in contact sports
What is the blood and nerve supply to the AC joint?
Blood: suprascapular & thoracoacromial
Nerve: suprascapular, lateral pectoral, axillary (from posterior cord of brachial plexus)
What is the function of the conoid and trapezoid ligaments?
Both are extrinsic ligaments of the AC joint, which hold joint together, deciding degree of shoulder separation.
Conoid: stops clavicle from elevating too far
-triangle, lies medially & in sagittal (vertically) plane
Trapezoid: prevents excessive rotation
-square, lies laterally & horizontally
What are the clavicular movements at the SC and AC joints?
[look up]
What are the grades of AC dislocation?
- AC ligaments stretched but not torn. CC ligaments intact.
- AC ligaments torn & disrupted. CC ligaments remain intact.
- AC & CC ligaments ruptured. Wide separation of joint.
* typically requires surgery to put joint back into position
What are the features of the glenohumeral (GH) joint?
- Between glenoid cavity and head of humerus
- Synovial ball-and-socket joint (multi-axial joint)
- Poor congruence b/w articular surfaces
- Glenoid labrum deepens socket (fibrocartilaginous ring)
- connective tissue yields more than bone - less nerve endings/pain
- Tendon of LH of biceps has intracapsular origin
What is the blood and nerve supply of the GH joint?
Blood supply: circumflex humeral arteries (anterior and posterior)
Nerve: suprascapular, axillary, lateral pectoral
What are the ligaments of the GH joint and what deficiencies are there in the articular capsule?
Intrinsic ligaments:
- coracohumeral
- glenohumeral (superior, middle, inferior)
Extrinsic:
- coracoacromial
- transverse humeral
Rotator cuff muscles act as dynamic ligaments providing posterior support.
Deficiencies in articular capsule:
- anterior GH ligaments
- inferior articular capsule
- anterolateral LH of biceps
What are the bursae at GH joint?
Subscapular, subacromial bursae
What mobility is there at GH joint?
- High mobility, reduced stability
- Rotator cuff muscles act as fixator ligaments: SITS
- Greatest stability when the 2 articular surfaces make maximal contact, which is during abduction and external rotation.
- Paradoxically, this is also position for dislocation.
What muscles act on shoulder joint anteriorly?
Deltoid Pectoralis major Coracobrachialis Biceps brachii Brachialis
Anterior deep:
Subscapularis
Coracobrachialis
Brachialis
