15.2 Anatomy: Joints of the upper limb Flashcards
What are the 4 features of a synovial joint?
Articular cartilage (avascular, aneural)
Fibrous capsule
Intrinsic/extrinsic ligamnets
Synovial membrane (lines all non-articular surfaces)
What is a labrum?
A fibrocartilagenous rim, deepens socket in ‘ball and socket joints’
What is special about fat pads?
Intra-articular but extrasynovial
What is the blood/nerve supply of discs/menisci?
Shock absorption, blood/nerve supply to outer third
What may bursae do?
Communicate with the joint cavity (sometimes synovial joint)
What are 3 features of stable joints?
Congruent (deep) articular surfaces
Tight capsule, strong ligaments
Limited ROM
What are 2 features of mobile joints?
- Stability dependent on short fixator/stabiliser muscles
- Susceptible to subluxation or dislocation
Where does the head of the humerus articulate?
WIth the Glenoid fossa (scapula)
What are the 2 processes above the Glenoid fossa?
Acromion and coracoid (medially)
What are the 2 ligments that attach to the clavicle?
Medial: costoclavicular
Lateral: coracoclavicular (stabilises)
What is the ratio between the movement of the scapula on the chest wall?
2:1 shoulder joint to scapular movement
Clavicle fracture:
Where does fracture occur?
Which direction does each break go?
Lat 1/3rd–>med 2/3rd
Lateral down, medial up
What does a disc increase?
The complexity of movement on each side
What type of joint is the sterno-clavicular? What reinforces it?
Intra-articular disc, strong capsule (very stable)
Costoclavicular (accessory) ligament limits movement
When can sternoclavicular subluxation occur? What can be impinged?
Motor vehicle accident, chest hits steering wheel.
Subclavian vessels (vein and artery) located directly behind
What type of joint is the acromioclavicular joint? What is it stabilised by?
Plane synovial joint (weak capsule), main stabiliser: coracoclavicular ligament
What are the different grades of acromioclavicular subluxation?
Grade 1: AC stretched
Grade 2: AC torn, disrupted
Grade 3: AC ruptured (joint separation)
What is a feature typical of a long bone?
Epiphyses at either end (also where muscles attach, traction)
Where are 3 sites susceptible to injury on the humerus?
Surgical neck (elderly, axillary nerve susceptible) Mid shaft (radial nerve) Supracondylar (median nerve and brachial artery endangered)
What are the 5 layers of the shoulder joint?
Layer 1: articular surfaces (unstable)
Layer 2: labrum and attachments (deepened)
Layer 3: capsule (loose, ROM in 3 planes)
Layer 4: muscles (rotator cuff)
Layer 5: coracoacromial ligament and bursa
Where are the deficiencies in the shoulder capsule?
Anteriorly:
long head of biceps
bursa (subscapular)
What is a frozen shoulder?
Also known as adhesive capsulitis: Capsule contracts (esp. if stationary for a long time, elderly etc.), decreased ROM
What muscles comprise the rotator cuff?
Teres minor, supraspinatus, infraspinatus and subscapularis
-(can act as prime movers but mainly stabilisers)
What can happen with a weak rotator cuff?
Humerus can slide upwards with pull of deltoid, ‘impingement’ of supraspinatus
What can occur if there is instability at the coracoacromial ligament and bursa?
Bursa can become impinged between bone and ligament (shoulder abduction esp. w/ weak RC)
What is the most common dislocation of the shoulder?
Anterior/inferior-force applied to abducted and externally rotated arm
(Post. less common, electric shock or epileptic fit)
What structure can be endangered by inferior dislocation of the shoulder?
Axillary nerve (supplying the deltoid and overlying skin)
What does the painful arc of movement refer to?
Shoulder painful in 60-120 degree abducted movement
