L2: Bones, ligaments and joints of the pectoral girdle Flashcards
clavicle
collar bone
articulates with sternum medially and scapula laterally
acts as strut, transferring forces between upper limb and axial skeleton
clavicle shape
S - shaped
medial 2/3 curves anteriorly
lateral 1/3 curves posteriorly
clavicle ends
medial end is bell-shaped and articulates with sternum - sternoclavicular joint
lateral end is flat and articulates with acromion - acromioclavicular joint
clavicle surface
smooth superior surface
rough inferior surface - impression for costoclavicular ligament, groove for subclavius, conoid tubercle, trapezoid line
clavicle weakest point
junction between medial 2/3 and lateral 1/3 - the straightest part of clavicle
typically fractures when excessive force transmitted through clavicle by upper limb
scapula - shoulder blade
sits on posterior thorax at level of 2nd - 7th ribs
articulates with clavicle at the acromioclavicular joint and humerus at glenohumeral joint
triangular shape, medial, lateral and superior borders
inferior, superior and lateral angle
scapula - anterior surface
subscapular fossa
coracoid process
acromion
neck
scapula- posterior surface
supraspinous fossa
infraspinous fossa
scapular notch
spine and acromion
scapula - lateral surface
glenoid fossa
supraglenoid tubercle
infraglenoid tubercle
scapula fractures
not very common
usually happen only in high-energy impacts e.g. road traffic accident
direct blunt force trauma to the blade, or falling from a height
humerus
long bone of the arm
articulates with scapular proximally - glenohumeral joint
articulates with bone of the forearm distally - ulna medially + radius laterally
radial groove on humerus
on posterior surface of shaft of humerus
contains radial nerve
sternoclavicular joint
articulation between clavicle, sternum and 1st costal cartilage
classified as an atypical saddle shaped synovial joint
typical features include:
joint capsule with inner synovium
synovial fluid
atypical feature
fibrocartilaginous disc in joint capsule between the bones - not hyaline
sternoclavicular joint - ligaments
anterior sternoclavicular ligament
posterior sternoclavicular ligament
interclavicular ligament
costoclavicular ligament
these ligaments are exceptionally strong, explaining why the clavicle tends to fracture instead of dislocating
acromioclavicular joint
*Articulation between lateral clavicle, and acromion of scapula
*Classified as atypical plane synovial join
acromioclavicular joint - ligaments
AC Joint is stabilised by coracoclavicular ligament
*Coracoclavicular ligament has two components:
*Conoid ligament
*Trapezoid ligament
*These ligaments tether the scapula superiorly to the clavicle whilst…
*AC ligament counteracts rotary forces from weight of arm
glenohumeral joint
classified as ball and socket synovial joint
most mobile joint of the body
unstable: sacrifices stability for mibility
GH joint instability
Ball and socket joint
*Shallow bony socket (glenoid fossa)
*Large bony ball (head of humerus)
*Lax and loose joint capsule
*To allow for movement
*Passively reinforced
*Glenoid labrum
*Joint ligaments
*Actively reinforced
*Muscles – rotator cuff
GH ligaments - passive stabilisers
glenohumeral ligaments
- superior
- middle
- inferior
coracohumeral ligament
other ligaments in GH joint
*Coracoacromial Ligament
*Prevents superior displacement of humerus
*Transverse Humeral Ligament
*Forms a roof over the bicipital groove
*Coracoacromial Arch
*Prevents superior dislocation
rotator cuff - active stabilisation
4 muscles that originate on scapula and insert on humerus
‘‘SITS’’
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
anterior GH joint dislocation
Most common dislocation because joint is least reinforced inferiorly
Antero-infero-medial displacement of humeral head
posterior GH joint dislocation
Rare - usually only occurs in:
Electric Shock
Epileptic Seizure
*“Light Bulb” Sign
what is a bursa
*A bubble of synovial membrane, contains synovial fluid
Acts as a soft cushion, preventing bone pressing against bone during moveme
bursitis
inflammation of the bursa, usually from overuse or trauma
