Scapular Region Anatomy

• The notes cover the scapular region and its associated anatomy

Learning Objectives

• Identify the main muscles in the scapular and scapulohumeral regions
• Explain the mechanics of scapular rotation in relation to shoulder movement

Scapular Region Muscles

• Muscles here connect the scapula to the humerus and facilitate movement at the shoulder joint
• These muscles are key for proper shoulder function and movement
• This group includes the rotator cuff muscles, deltoid, and teres major

Rotator Cuff Muscles

• Supraspinatus
  • Originates at the supraspinous fossa
  • Inserts at the greater tuberosity
  • Suprascapular nerve provides innervation
  • Initiates abduction in the 0-15° range
• Infraspinatus
  • Originates at the infraspinous fossa
  • Inserts at the greater tuberosity
  • Axillary nerve provides innervation
  • Responsible for the lateral rotation of the arm
• Teres Minor
  • Originates at the lateral border of the scapula
  • Inserts at the greater tuberosity
  • Axillary nerve provides innervation
  • Contributes to the arm's lateral rotation
• Subscapularis
  • Originates at the subscapular fossa
  • Inserts at the lesser tuberosity
  • Subscapular nerve innervates
  • Causes medial rotation

Rotator Cuff Injuries

• Injury or disease to the musculotendinous rotator cuff can cause shoulder instability
• Trauma has the potential to tear or rupture one or more tendons of the rotator cuff muscles
• The supraspinatus tendon ruptures most often
• Supraspinatus injuries are often linked to a painful abduction

Teres Major

• Originates at the lateral border of the scapula
• Inserts on the medial lip of the bicipital groove of the humerus
• Lower subscapular nerve provides nerve supply
• Responsible for extension, adduction, and medial rotation of the humerus, such as during swimming

Deltoid

• Originates at the lateral third of the clavicle, acromion, and spine of the scapula
• Inserts at the deltoid tuberosity
• Axillary nerve provides innervation
• Consists of three sets of fibers:
  • Anterior fibers: responsible for flexion and medial rotation
  • Middle fibers: responsible for abduction within the 15°-90° range
  • Posterior fibers: responsible for extension and lateral rotation

Abduction of the Arm

• Supraspinatus initiates abduction from 0-15°, innervated by the suprascapular nerve
• Deltoid (middle fibers) abducts the arm from 15°-90°, innervated by the axillary nerve

Transverse Scapular Ligament

• Attaches to the suprascapular notch
• The subscapular nerve (C5,6) travels below, and the subscapular artery goes above it

Axillary Nerve Injury

• Causes can include fracture of the surgical neck of the humerus and shoulder dislocation
• Results in paralysis of the deltoid and teres minor
• Causes loss of abduction between 15-90 degrees
• Leads to a flat shoulder deformity

Testing the Deltoid Muscle

• Examiner resists the patient’s abduction of the limb
• Contraction of the middle part of the deltoid can be palpated if the muscle is functioning properly

Case Scenarios

• A 15-year-old weightlifter has an avulsion fracture of the greater tubercle of the humerus and difficulty initiating abduction, indicating a supraspinatus muscle injury

• X-ray reveals a fracture of the proximal humerus, suggesting potential damage to the axillary nerve