Shoulder Anatomy

Aka: Shoulder Anatomy, Shoulder

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II. Anatomy

  1. Bone and Ligament
    1. orthoAnteriorBoneShoulder.jpgAlso available as a Poster size image. See printing instructions and image restrictions.
    2. orthoPosteriorBoneShoulder.jpgAlso available as a Poster size image. See printing instructions and image restrictions.
    3. orthoArmShoulderJointGrayBB326.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
    4. orthoArmShoulderJointGrayBB327.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
    5. orthoArmShoulderJointGrayBB328.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  2. Muscles
    1. ShoulderAnteriorBiceps.jpg
    2. orthoArmShoulderMusclesLtGrayBB410.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
    3. orthoArmShoulderMusclesLtDeepGrayBB411.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
    4. orthoArmShoulderMusclesLtPosteriorGrayBB412.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)

III. Anatomy: Bones

  1. Scapula
    1. Scapular spine
      1. Third thoracic Vertebrae
    2. Scapular inferior angle
      1. Eighth thoracic Vertebrae (7th rib)
  2. Clavicle
  3. Humerus

IV. Anatomy: Muscles

  1. Muscles attaching Axial skeleton to Scapula
    1. Trapezius
    2. Levator Scapulae
    3. Rhomboids
    4. Serratus anterior
  2. Muscles attaching Axial skeleton to Humerus
    1. Latissimus dorsi
    2. Pectoralis major

V. Anatomy: Joints and Articulations

  1. Glenohumeral joint (GH Joint)
    1. Glenoid of Scapula meets humeral head
    2. Golf ball on golf tee
      1. Articulation with bone: 30%
      2. Articulation with glenoid labrum: 75%
  2. Posterior Chest Wall (Scapulothoracic articulation)
  3. Acromioclavicular Joint (AC Joint)
    1. Acromion of Scapula meets the clavicle
  4. Sternoclavicular Joint (SC Joint)
    1. Four ligaments (in addition to a saddle-like structure) stabilize the joint
      1. Anterior sternoclavicular ligament
      2. Posterior sternoclavicular ligament
      3. Interclavicular ligament
      4. Costoclavicular ligament

VI. Anatomy: Nerves

  1. Rotator cuff is innervated by Brachial Plexus derived nerves
    1. Suprascapular nerve
      1. Innervates supraspinatus and infraspinatus
    2. Axillary nerve
      1. Wraps around the Humerus surgical neck
      2. Innervates teres minor
      3. Also innervates the deltoid Muscle (not part of the rotator cuff)
    3. Subscapular nerve
      1. Innervates subscapularis

VII. Anatomy: Subacromial Space

  1. Coracoclavicular arch forms the roof of the subacromial space
    1. Coracoid process
    2. Coracoacromial ligament
    3. Acromion process
  2. Rotator cuff composition (mnemonic: SITS Muscles)
    1. Anterior Rotator Cuff
      1. Subscapularis Muscle
    2. Posterior Rotator Cuff
      1. Infraspinatus Muscle
      2. Teres Minor Muscle
    3. Superior Rotator Cuff
      1. Supraspinatus Muscle
  3. Subacromial bursae
    1. Separates cuff from overlying coracoacromial arch
    2. Includes subdeltoid bursa and subcoracoid bursa
  4. Image
    1. ShoulderAnteriorRotatorCuff.jpg
    2. orthoShoulderSuperior.png

VIII. Physiology: Function

  1. Scapula stabilized prior to arm movement
  2. Rotator Cuff (Musculotendinous)
    1. Steadies humeral head in glenoid
    2. Results in humeral head descent
  3. Scapulothoracic Musculature
    1. Results in forward and lateral Scapula movement
    2. Initiates first 60-70 degrees of Shoulder Abduction
  4. Glenohumeral Musculature
    1. Deltoid and supraspinatus Muscles
    2. Accounts for last two thirds of Shoulder Abduction

IX. Physiology: Muscle action at Glenohumeral joint

  1. Shoulder Abduction
    1. Middle deltoid Muscle
    2. Supraspinatus Muscle
  2. Shoulder Adduction
    1. Pectoralis major Muscle
    2. Latissimus dorsi Muscle
  3. Shoulder Flexion
    1. Anterior deltoid Muscle
    2. Coracobrachialis Muscle
  4. Shoulder Extension
    1. Posterior deltoid Muscle
    2. Latissimus dorsi Muscle
    3. Teres major Muscle
  5. Shoulder Internal Rotation
    1. Pectoralis major Muscle
    2. Latissimus dorsi Muscle
    3. Teres major Muscle
    4. Subscapularis Muscle
  6. Shoulder External Rotation
    1. Infraspinatus Muscle
    2. Teres Minor Muscle

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