Shoulder Anatomy

Aka: Shoulder Anatomy, Shoulder, Glenohumeral Joint, Rotator Cuff

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II. Anatomy: Joints and Articulations

  1. General
    1. Shoulder joint is composed of 3 synovial joints (GH, AC, SC) and a scapulothoracic articulation
  2. Glenohumeral Joint (GH Joint)
    1. Glenoid of Scapula meets humeral head
      1. Analogous to a Golf ball on golf tee
    2. Shoulder joint capsule (stabilizes the Shoulder joint)
      1. Glenohumeral ligaments
        1. Surrounds the Shoulder joint and attaches to the glenoid labrum
      2. Glenoid labrum
        1. Cartilage in the shape of a donut that surrounds the glenohurmeral joint
        2. Articulation with glenoid labrum: 75% (remainder of articulation is with bone)
  3. Posterior Chest Wall (Scapulothoracic articulation)
  4. Acromioclavicular Joint (AC Joint)
    1. Acromion of Scapula meets the clavicle
  5. 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

III. Anatomy: Bones

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

IV. Anatomy: Muscles (including Rotator Cuff)

  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
  3. Rotator Cuff (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
  4. Images
    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)

V. Anatomy: Nerves

  1. Rotator Cuff is innervated by Brachial Plexus derived nerves
  2. Suprascapular nerve
    1. Innervates supraspinatus and infraspinatus
  3. 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)
  4. Subscapular nerve
    1. Innervates subscapularis

VI. Anatomy: Vessels

  1. See Vascular Anatomy of the Shoulder
  2. Artery
    1. Shoulder
      1. orthoArmShoulderArteryAntAxillaryGrayBB523.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
      2. orthoArmShoulderPosteriorArteryGrayBB521.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
      3. orthoArmShoulderPostArteryGrayBB524.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
    2. Upper Arm
      1. orthoArmHumerusBrachialArteryGrayBB525.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
      2. orthoArmCvAntArteryGrayBB1235.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  3. Vein
    1. Shoulder
      1. orthoArmShoulderVeinAxillaryGrayBB576.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
    2. Upper Arm
      1. orthoArmAntVeinGrayBB574.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)

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
    1. See Muscles above
  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. Shoulder Joint
    1. Glenohumeral rotation
      1. Accounts for first 50% of Shoulder joint movement
      2. Scapula stabilized prior to initial arm movement
    2. Scapulothoracic rotation (Scapula rotation over the underlying ribs)
      1. Accounts for remainder of Shoulder joint movement
  2. Musculature
    1. Rotator Cuff (Musculotendinous)
      1. See Muscles above
      2. Stabilizes humeral head in glenoid
      3. Results in humeral head descent
    2. Scapulothoracic Musculature
      1. Results in forward and lateral Scapula movement
      2. Initiates first 60-70 degrees of Shoulder Abduction
    3. Glenohumeral Musculature
      1. Deltoid and supraspinatus Muscles
      2. Accounts for last two thirds of Shoulder Abduction
  3. Specific 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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