130 - Joints of Upper Limb 1 - Shoulder Complex Flashcards
Components of synovial joints 1 2 3 4 5
1) Articular cartilage – avascular & aneural
2) Fibrous capsule – may be reinforced by stabilizer muscles
3) Capsule strengthened by intrinsic ligaments
4) Extrinsic (accessory ligaments) may be primarystabilisers
5) Synovial membrane - linesall non-articular surfaces
Consequence of having a lot of hyaline cartilage on a bone
Only will have a narrow area where blood vessels can enter (hyaline cartilage is avascular).
Therefore bone is vulnerable to necrosis
Structure from which most pain comes in a broken bone
Periosteum
What lines all non-articular surfaces in a synovial joint?
Synovial membranes
Examples of 'special' synovial joint structures 1 2 3 4 5 6
1) Labrum
2) Fat pad
3) Intra-casular tendon
4) Discs, menisci
5) Bursae
6) Ligaments
Labrum
A fibro-cartilagenous rim that deepens the socket in ball-and-socket joints.
Increases congruence of a joint quite markedly (EG: by 1/3 in shoulder joint)
Fat pad
Intra-articular, extra-synovial structures.
Fill out irregularly-shaped structures in joints
Ligaments
Thickenings of capsule (intrinsic) or extrinsic ligaments.
Stabilise joints
What can a ligamentous injury in children involve?
An avulsion injury (because ligament is stronger than growing bone)
Discs and menisci
Shock absorb.
Might bear weight.
Have blood and nerve supply to outer third.
EG: In knee
Bursae
Can communicate with joint cavity.
If it can communicate, can have flow of synovial fluid into communicating bursa, EG: In the case of infection.
What does stability of mobile joints often depend on?
Short fixator or stabiliser muscles
Joints of the clavicle
1
2
Sternoclavicular joint.
Acromioclavicular joint.
Feature on the posterior aspect of scapulae
Spinous process.
Divides into supraspinous fossa and infraspinous fossa
How do muscles attach to scapula?
With muscle attachment, not tendinous attachment.
Lateral fossa on scapulae
Glenoid fossa
Processes overhanging gelnoid fossa
Acromion process.
Coracoid process
Where does the acromion process come from?
Part of the spinous process of the scapula
Function of clavicles
Orientates the shoulder laterally for greater ROM.
Where does clavicle articulate with midline?
On bulbous part
Why is the clavicle curved?
So that it doesn’t impinge on structures (EG: blood vessels, nerves) that travel under the clavicles
Two ligamentous attachments to clavicle
Both on underside of clavicle.
Costoclavicular ligament
Coraco-clavicular ligament
How do the clavicles orientate the shoulders?
Gleno-humeral rhythm.
Clavicles change orientation with shoulder movement to orientate glenohumeral joint.
About 2:1 ratio of movement for shoulder joint to clavicle.
Most common site of clavicular fracture
Between lateral 1/3 and medial 2/3 (where there is the greatest change in curvature).
Mechanics of clavicular fracture
Sternocleidomastoid pulls medial clavicle upwards.
Key features of sternoclavicular joint
1
2
1) Intra-articular disc & strong capsule
2) Very stable joint Costoclavicular (accessory) ligament – main limitation to movement
Main limiter of sternoclavicular joint movement
Costoclavicular ligament
Effect of a disc on a joint
Increases the complexity of movement, one of which is rotation.
Movements of the sternoclavicular joint
1
2
- Disc increases complexity of movement on each side of it
* Elevation/depression with rotation about longitudinal axis
Costoclavicular ligament
Joins first rib and medial clavicle.
An accessory ligament that is the main limiter of movement in the costoclavicular joint
How common is sternoclavicular subluxation?
Very rare.
Often associated with trauma
Biggest danger with sternoclavicular subluxation
Subclavian artery and vein can be endangered
Features of acromioclavicular joint 1 2 3 4
1) Plane synovial joint – articular surfaces in sagittal plane
2) Weak capsule
3) Main stabiliser coracoclavicular ligament - 2 parts separated by bursa
4) Both parts prevent upward rotation of clavicle at AC joint
Arrangement of articular surfaces that makes acromioclavicular joint liable to be injured
Articulate in sagittal plane, so face in direction most likely to encounter force
Concentric rings of structures in glenohumeral joint 1 2 3 4 5
- Layer 1 - bones (most interior layer)
- Layer 2 - labrum – deepens socket
- Layer 3 - capsule –reinforced by intrinsic ligaments
- Layer 4 - tendons –“rotator cuff”
- Layer 5 – coraco-acromial (accessory) ligament/arch & sub-acromial bursa)
Fracture sites of humerus
1
2
3
- Surgical neck (common in elderly) – endangers axillary nerve
- Mid-shaft – endangers radial nerve
- Supracondylar – endangers median nerve & brachial artery
What does a mid-shaft fracture of the humerus endanger?
Radial nerve
What does a supracondylar fracture of the humerus endanger?
Median nerve, brachial artery
Traction epiphyses
Epiphyses to which a muscle attaches
What does a fracture of the humerus at the surgical neck endanger?
Axillary nerve
What makes the glenohumeral joint unstable?
Disproportionately large head of the humerus to the shallow glenoid fossa. Poor congruence.
When is the glenohumeral joint particularly unstable?
Abduction
Where does the capsule of the glenohumeral joint travel?
Past the anatomical neck to the surgical neck.
Allows for greater ROM
Attachment of biceps tendon
Superior attachment to glenoid labrum
Shape of glenohumeral capsule
Loose (folded inferiorly) to allow ROM in 3 planes - attaches to anatomical neck above; surgical neck below
‘Deficiencies’ anteriorly for: - long head of biceps - bursa (subscapular)
Glenohumeral capsule deficiencies
‘Deficiencies’ anteriorly for: - long head of biceps - bursa (subscapular)
What can happen if there is too little movement of the shoulder?
GLenohumeral capsule can constrict, leading to a decrease in ROM.
‘Frozen shoulder’
Bursa that goes through deficiency in glenohumeral capsule
Subscapularis bursa
Location of rotator cuff muscles
‘Rotator cuff’ muscles located deep to deltoid – originate from scapula and insert into capsule – although have prime mover actions primary role as stabilizers
Muscles of the rotator cuff 1 2 3 4
1) Supraspinatus
2) Infraspinatus
3) Subscapularis
4) Teres minor
Subscapularis
Internal rotation
Supraspinatus
Attaches to superior part of capsule.
Passes under coracoacromial ligament
Common rotator cuff pathology
If rotator cuff weak, humerus susceptible to slide upwards with pull of deltoid – may lead to entrapment (‘impingement’) especially of supraspinatus.
This is because supraspinatus runs under coracoacromial ligament.
Least significant stabiliser of glenohumeral joint
Coracoacromial ligament and bursa
What is the coracoacromial bursa susceptible to?
Irritation during shoulder abduction.
