joints of the shoulder

Glenohumeral joint

BOne

Glenoid

· slightly greater radius of curvature than humeral head

· 1/4 of surface area of proximal humeral articular surface

· deepened by glenoid labrum

· rim of fibrocartilage attached to margins of labrum

· cartilage thinner peripherally than centrally

Humeral head

· retroverted 15-35^o (av. 25^o)

· neck-shaft angle 115-130^o

Blood supply

· anterior humeral circumflex a

· primary supply by anterolateral branch called arcuate a

· continues lateral to long head of biceps

· perfuses entire epiphysis of humeral head

· posterior humeral circumflex a

· supplies small area in posteroinferior aspect of humeral head

ligaments

Capsule

· glenoid

· attached to margins of glenoid and further back on neck of scapula

· humerus

· attached to articular margins of humeral head (anatomical neck) except inferiorly

· here attached to surgical neck 1 fingerbreadth below articular margin

· forms transverse ligament where bridges gap between greater and lesser tuberosities

· anterior defect for communication with subscapularis bursa

· glenohumeral ligaments are thickenings of capsule

Synovial membrane

· attached around glenoid labrum and articular margin of head of humerus

· covers bare area of surgical neck of humerus at upper end of shaft that lies within capsule

· herniates through hole in front of capsule to communicate with subscapularis bursa

· may communicate with infraspinatus bursa

· invests long head of biceps in tubular sleeve

· reflected back along tendon to transverse ligament and floor of intertubercular groove

Glenohumeral

Inferior glenohumeral

· described as a complex

· anterior and posterior bands

· originate from anteroinferior and posteroinferior labrum

· intervening inferior axillary pouch

· bands connected to proximal humerus in V attachment

Middle glenohumeral

· originates from anterior labrum

· passes down to anterior humeral head

Superior glenohumeral

· originates from superior labrum (anterior to biceps)

· passes to superior humeral head

Coracohumeral

· strong

· runs from undersurface of coracoid to capsule

· in rotator interval

· attaches

· to margin of greater tuberosity

· along transverse ligament

Coracoacromial

· runs from anteromedial border of acromion

· undersurface

· in front of AC jt

· fans out to lateral border of coracoid process

Bursae

Subacromial

· lies between coracoacromial ligament and rotator cuff

· upper layer attached to coracoacromial ligament

· lower layer attached to tendon of supraspinatus

· does not normally communicate with shoulder joint

Subscapularis

· between muscle and bare area at glenoid angle of scapula

· extends laterally

· communicates with shoulder joint through gap in anterior part of capsule

Infraspinatus

· between muscle and bare are at glenoid angle of scapula

· may communicate with shoulder joint

nerve supply

· from axillary, musculocutaneous and suprascapular nerves

Sternoclavicular joint

· synovial joint

· but surfaces covered by fibrocartilage

· sternal end of clavicle projects above sternum

· only lower half lies opposite sternal articular facet

· separated by fibrocartilage meniscus

· meniscus attached to

· capsule

· medial end of clavicle

· 1st costal cartilage

Ligaments

Capsule

· thickened anteriorly and posteriorly as sternoclavicular ligaments

· anterior weaker

Interclavicular ligament

· joins upper borders of sternal ends of clavicles

· attached to suprasternal notch

Costoclavicular ligament

· attaches clavicle to 1st rib and cartilage

· just lateral to SC jt

· 2 laminae from rib

· anterior runs laterally

· posterior runs medially

· very strong

movements

· fulcrum is costoclavicular ligament

· in both planes

· up and down movement

· movement between clavicle and disc

· forward and backward movement and rotation

· movement between disc and sternum

stability

· ligaments, esp. costoclavicular

Acromioclavicular joint

· synovial joint

· surfaces covered by fibrocartilage

· incomplete fibrocartilage in upper part

Ligaments

Capsule

· surrounds joint

· thickened superiorly as acromioclavicular ligament

Coracoclavicular ligament

· two parts

Conoid

· inverted cone

· from knuckle of coracoid

· to conoid tubercle on undersurface of clavicle

Trapezoid

· from trapezoid ridge on coracoid

· to trapezoid ridge on undersurface of clavicle

Movements

· passive

· scapular movements cause corresponding clavicular movements

1. protraction and retraction

· vertical axis through conoid ligament

· movement between acromion and fibrocartilage

2. rotation

· axis between AC jt and conoid ligament

· fulcrum through coracoclavicular ligament

· movement between fibrocartilage and clavicle

3. elevation and depression

· minimal AC jt movement

stability

· provided by coracoclavicular ligament

· fractures between costoclavicular and coracoclavicular ligaments