Upper Limb

SHOULDER TO ELBOW

Discuss the anatomy of the glenohumeral joint (30 marks)

DESCRIPTION

• Glenohumeral joint is the main component of the shoulder complex
• Multiaxial ball-and-socket Synovial joint
• Connects head of humerus —> glenoid fossa of scapula
• Joint surrounded by synovial lined fibrous capsule
• glenoid deepened by labrum (fibrocartilage rim)
• hyaline cartilage thin in central glenoid and in periphery of humeral head
• only limited areas of the article surfaces are in contact in any position – allowing humeral head to slide and/or slide freely on glenoid surface
• maximum congruity in abduction + lateral rotation (throwing a ball) as it tightens the ligaments = “close-packed position”
• 1-2mL synovial fluid

COMPONENTS OF GLENOHUMERAL JOINT

• HUMERAL HEAD
  • broader distal articulation about 1/3 of sphere
  • surface 4x larger than glenoid cavity (no labrum)
  • distal neck that has the distal attachments of the synovial membrane and ligaments
  • greater and lesser tubercles laterally have insertions of the rotator cuff muscles
  • 12-15 degree of ante version
  • hyaline cartilage covers
• GLENOID FOSSA + LABRUM
  • pear-shaped ~ concave/deficient superior anteriorly
  • hyaline cartilage lines the joint surface – cartilage thins centrally
  • more concave then the humeral head convexity
  • covers a smaller percentage of humeral surface
  • glenoid labrum increase “depth” & “area”
  • glenoid labrum is fibrocartilage

• SYNOVIAL MEMBRANE
  • lines capsule
  • sleeve of synovial membrane invests tendon of the long head of biceps
  • continuous with subscapularis bursa (always communicates with joint)
  • no communication with subacromial-subdeltoid bursa
  • variant – communicates with the subcoracoid bursae
• FIBROUS JOINT CAPSULE
  • thin fibrous capsule forms loose sleeve and puts no restraints on joint movement except in “close packed” position
  • glenoid attachment: base of glenoid labrum
    • posterior at base of glenoid labrum
    • anterior more variable – base or scapular neck (<1cm or >1cm from labrum)
  • humerus attachment: follows articular margin around anatomic neck except inferiorly where it extends to surgical neck= hangs loosely below joint

• LIGAMENTS
  • Tendon of the long head of biceps + transverse humeral ligament
    • tendon of long head of biceps attached to supraglenoid tubercle + labrum
    • passes over humeral head and descends into inter tubercular groove
    • Transverse humeral ligament = capsular fibres bridge the groove to keep tendon in place
    • Tendon is a main stabiliser of joint
    • lateral rotation of humerus makes the inter tubercular groove better accessible for palpation

• Coracohumeral ligament (superior)
  • thickening in the capsule
  • base of the coracoid process —> greater tubercle
  • supports the weight of the pendant arm
  • however with the arm abducted, the ligament is lax and the strength of the joint depends entirely on the muscles of the tendinous cuff
  • fuses with supraspinatus tendon, subscapularis tendon, joint capsules and superior glenohumeral ligament 

• Glenohumeral ligaments
  • strengthen and fuse with joint capsule anteriorly
    • superior (superior glenoid —> lesser tuberosity)
    • middle (superior glenoid —> lesser tuberosity)
    • inferior (anterior + posterior bands + axillary pouch)
    • **subscapularis bursae communication between
      • superior + middle glenohumeral ligament: “foramen of Weitbretcht”
      • middle + inferior glenohumeral ligaments “foramen of Rouviere”
    • Tendinous cuff
      • ligaments of rotator cuff muscles
    • Coracoacromial ligament
      • anterior 2/3 coracoid —> tip of acromion
      • coracoacromial arch = coracoid process + coracoacromial ligament + acromion
      • forms a secondary socket for the head of the humerus
      • movement beneath the arch is aided by the subacromial and sub deltoid bursa (which often fuse)

• Other ligaments of shoulder complex not directly at glenohumeral joint:
  • coracoclavicular ligament
  • acromioclavicular ligament (superior + inferior)
  • superior transverse scapular ligament
  • inferior transverse scapular ligament

• BURSAE
  • subscapularis bursae
  • subacromial-subdeltoid bursae – adherent to undersurface of acromion
  • subcoracoid bursae – between subscapularis tendon and coracobrachialis/short head of biceps
  • infraspinatus bursa – between infraspinatus and joint capsule
  • +/- deep to coracobrachialis
  • +/- between teres major and long head triceps
  • +/- anterior and posterior to latissimus dorsi tendon
  • +/- superior to acromion

• ROTATOR CUFF
  • tendons interdigitate and form continuous band that attaches to humerus
  • suprapinatus : superior facet +/- middle of greater tuberosity
    • direct component —> anterior portion of tuberosity
    • posterior oblique component —> undercuts infraspinatus at posterior portion of tuberosit
  • infraspinatus : middle facet of greater tuberosity <— infraspinatus fossa
  • teres minor : inferior facet of greater tuberosity <— lateral scapular border
  • subscapularis : lesser tuberosity <— subscapular fossa

• JOINT STABILISERS – 
  • Superior support:
    • coracoacromial arch
    • long head of tendon
    • rotator cuff muscles
  • Anterior support:
    • subscapularis tendon,
    • anterior capsule, synovial membrane, anterior labrum,
    • superior + middle + inferior glenohumeral ligaments
  • Posterior support :
    • infraspinatus tendon, teres minor tendon,
    • posterior capsule, synovial membrane, posterior labrum,
    • inferior glenohumeral ligaments
    • rotator cuff muscles: teres minor and infraspinatus

RELATIONS

• Superior:
  • coracoacromial arch
  • long head of biceps and biceps tendon sheath (connected to glenohumeral joint space)
  • deltoid muscle
  • acromioclavicular arch
  • subacromial bursa (superior)
  • subdeltoid bursa (more lateral-superior)

• Anterior:
  • subscapularis tendon
  • axillary vessels + brachial plexus
  • glenohumeral ligament and lax part of ligament with synovial membrane,
  • brachial plexus

• Posterior:
  • supraspinatus, infraspinatus, teres minor
  • latissimus dorsi,
  • posterior part of deltoid

ARTERY

• Articular branches of anterior and posterior humeral circumflex arteries (from axillary artery)
• Suprascapular artery

NERVE (Hilton’s Law)

• Axillary nerve
• Suprascapular nerve

LYMPH

• Subclavian LNs
• Supraclavicular LNs

RANGE OF MOTION of Glenohumeral joint

• Flexion – pec major, deltoid, coracobrachialis, biceps brachii
• Extension – deltoid, teres major (against resistance +latissimus dorsi & pec major)
• Abduction – deltoid, supraspinatus (+downward traction: supscapularis, infraspinatus, teres minor)
• Adduction
• Circumduction
• Medial rotation – pec major, deltoid, latissimus dorsi, teres major (+ if arm at side: subscapularis)
• Lateral rotation – infraspinatus, deltoid, teres minor

VARIANTS

• Bicep muscle variant
• absent long head of biceps
• origin of long head of biceps from inter tubercular groove or joint capsule
• additional heads of biceps

• Labrum variants: size, shape, appearance (most common anterior-superior region)
  • Buford complex
  • sublabral foramen

• Glenohumeral ligament variants
  • absent/diminutive Middle Glenohumeral ligament 30% population

• Anterior joint capsule insertion
  • type 1 – tip of base of labrum
  • type 2 – scapular neck <1cm from labrum
  • type 3 – scapular neck >1cm from labrum