Download LECTURE 5: GLENOHUMERAL JOINT

LECTURE 5: GLENOHUMERAL JOINT
OBJECTIVES:
Congruency: decreased congruency at the glenohumeral joint allows for greater mobility but
results in less stability.
Surgical neck: below tubercles, frequently fractured
Anatomical neck: articulation of joint capsule, oblique angle
Acromion process: superior to joint, prevents superior dislocation
Coracoid process: medial to joint, muscle attachment, provides canal for brachial plexus
Joint capsule:
- Attachments: anatomical neck of humerus, glenoid cavity, root of coracoid process
- Strength: loose to allow freedom of movement, inferior part is weakest
- Synovial membrane: lines capsule and extends to include long head of biceps tendon in
capsule and also encloses subacromial bursa, has 2 openings
Glenoid labrum:
- Structure: fibrocartilagenous collar
- Attachments: margins of glenoid fossa, continues superiorly with tendon of long head of
biceps
- Function: deepens articulation for greater congruency
Ligaments:
Coracohumeral
Transverse humeral
Glenohumeral
Coracoacromial
Location
Coracoid process to
humerus
Bridges bicipital
groove
Between scapula and
humerus
Between coracoid
and acromion
processes
Attachments
Base of coracoid
process to greater
tubercle of humerus
Greater tubercle to
lesser tubercle
Glenoid labrum at
supraglenoid tubercle
and base of coracoid
process to anatomical
neck of humerus
Base of coracoid
process to greater
tubercle of humerus
Function
Reinforce
anterosuperior aspect
of the GHJ
Tethers long head
biceps brachii
Reinforce
anterior/inferior
aspect of joint
capsule
Prevents superior
displacement of
humerus
Dynamic ligament: a muscle acting as a ligament at a joint
- Advantages: active support, tendons blend to reinforce capsule, protection, stability
- Disadvantages: require energy, reduced support if muscle damaged
- Rotator cuff of GHJ: supraspinatus, infraspinatus, subscapularis, teres minor
Stabilisation:
- Articular surfaces: not very congruent, congruency increased by glenoid labrum
- Ligaments: glenohumeral and coracohumeral
- Muscles: rotator cuff
Rotator cuff:
- Rotatory function: two forces equal in magnitude, opposite in direction, applied to same
object at a different point will produce rotatory motion
- Stability function: pulls humeral head into scapula because of opposition of line of
gravity and line of pull of the muscles
Innervation: capsule, ligaments and smooth muscle of blood vessels
- GSA’s: proprioception
- GVE’s: arteries
- Suprascapular nerve, axillary nerve, lateral pectoral nerve
Subacromial space:
- Boundaries: acromion, coracoacromial ligament, coracoid process, glenohumeral joint
capsule
- Contents: subacromial bursa, supraspinatus tendon, supraspinatus bursa
- Clinical problems: bursitis caused by inflammation or degeneration of supraspinatus
tendon, affects lifting and abduction
Inferior-anterior dislocation:
- head of humerus slips out of glenoid cavity inferiorly and anteriorly
- can damage axillary nerve and posterior circumflex humeral artery
Fractured surgical neck of humerus:
- can damage posterior circumflex humeral artery and axillary nerve
- more frequently fractured than anatomical neck