L6.1 Shoulder joint

Question 1

What is the shoulder complex comprised of?

Answer 1

• Pectoral girdle
  
  • Manubrium
  • Clavicle
  • Scapular
• Humerus

Question 2

Sternoclavicular joint

Ligaments, nerve, blood supply

Answer 2

• Connects UL with thorax
• Saddle (biaxial) joint
  
  • Has articular disc which divides space into 2 cavity → complex joint
  • Permits multiple range of movement
• Ligaments:
• Intrinsic:
  
  • Sternoclavicular - ANT&POS
  • Interclavicular - From one clavicle to another across jugular notch
• Extrinsic:
  
  • Costoclavicular - From base of 1st rib → clavicle (lat of sternoclavicular ligament)
• Nerve supply:
  
  • Subclavius
• Blood supply:
  
  • Internal thoracic
  • Suprascapular

Question 3

Injuries of the sternoclavicular joint

Answer 3

• Dislocation uncommon, subluxation more common
  
  • Arises from direct trauma in front of hcest
  • Vessels at root of neck susceptible to injury
  • POS subluxation (uncommon) → dangerous → impinge on important blood vessels

Question 4

Acromioclavicular joint

Ligaments, nerve, blood supply

Answer 4

• Acromial end + acromion process of scapula
• Plane joint
  
  • Also have articular disc, but only partially
  • Movements complementary to sternoclavicular joint
• Ligaments:
  
  • Intrinsic
    
    • Acromioclavicular
  • Extrinsic
    
    • Coracoclavicular (functionally most important and stable)
      
      • Conoid part (med, shaped like a cone)
        
        • Prevents clavicle moving too far superiorly
      • Trapezoid (lat, right angle to conoid)
        
        • Prevents excess rotation of clavicle on scapula
• Nerve supply:
  
  • Supraclavicular
  • Axillary
  • Lat pectoral
• Blood supply:
  
  • Suprascapular
  • Thoracoaromial

Question 5

Injuries of the acromioclavicular joint

Answer 5

• Dislocation: Shoulder separation (6 degrees but 3 important ones)
• 1) AC lig stretched, not torn
  
  • Coracoclavicular lig intact
• 2) AC lig torn & disrupted
  
  • Coracoclavicular lig intact
• 3) Ac & Coracoclavicular lig torn
  
  • Wide separation of joints (complete shoulder separation)

Question 6

What is the effect of the SC and AC joint movements?

Answer 6

• Movement of SC & AC joints (working together)
  
  • Allows scapula to be rotated
    
    • Glenoid cavity move superiorly
  • Trapezius & serratus ANT work together

Question 7

Glenohumeral joint

Ligaments, Nerve, blood supply

Answer 7

• Ball & Socket
  
  • Labrum encircles cavity (fibrocartilaginous → avascular & aneural → allows movement of bones without pain)
• Ligaments:
• Intrinsic:
  
  • Coracohumeral lig
  • Glenohumeral (Sup, Mid, Inf - INF has ANT/POS fibres and are lax)
• Extrinsic:
  
  • Coracoacromial
  • Transverse humeral
• Nerve supply:
  
  • Suprascapular
  • Axillary
  • Lat pectoral
• Blood supply
  
  • Circumflex humeral A

Question 8

Areas of weakness/deficiencies in the articular capsule

Answer 8

• ANT glenohumeral lig
• INF articular capsule
• Anterolateral long head of biceps

Question 9

Injuries of the GH joint?

Answer 9

• Dislocation of GH joint:
• ANT & INF (due to laxity of INF lig)
• POS (less common) - in Add & Internally rotated
  
  • From shock/epilepsy

Question 10

What is the position with maximal stability of the GH joint?

Answer 10

• Ab, external rotation, extended
• But at this position, there is the greatest risk of dislocation

Question 11

What are the 2 physiological joints

Answer 11

Subdeltoid

Scapulothoracic

Question 12

Subdeltoid joint

Answer 12

• Btw supraspinatus & GH joint
• Subacromial burase → ↓friction → allows movement to take place
• May result in painful arc syndrome

Question 13

Scapulothoracic joint

Answer 13

• Btw serratus & thorax
• Btw serratus & scapula
• Movement of scapula in 1:2 ratio to GH joint
  
  • Arms extended 180o, GH joint 120o, scapulothoracic joint 60o

Question 14

What is the role of the rotator cuff muscles?

Answer 14

• dynamic fixator ligs
• Pull on head of humerus

Question 15

Injuries of the rotator cuff muscles?

Answer 15

• Adhesive capsulitis (frozen shoulder)
  
  • Surrounding tissues inflamed
• Subacromial bursitis
  
  • Burase inflammed from repetitive action from shoulder abduction