Scapula

What are the articulations of the scapula?

• clavicle: acromioclavicular joint

• humerus: glenohumeral joint

Describe the scapula’s Angles, borders, surfaces, fossa and processes

• 3 angles:

  • lateral: Bears the glenoid cavity

  • superior: Near C7/T1 spinous process

  • inferior: near T7 spinous process (important palpation landmark)

• 3 borders:

  • superior: contains the suprascapular notch (for= suprascapular nerve)

  • lateral: Thick, extends from glenoid cavity to inferior angle

  • medial: Parallel to the spine

• 2 surfaces: costal and posterior

• 3 processes: Acromion, Spine and
  coracoid process

• 3 Fossa:

  • Supraspinous fossa: superior to spine (posterior)

  • Infraspinous fossa: inferior to spine, larger (posterior)

  • Subscapular fossa - in the costal surface of the scapula

What are the key landmarks of the scapula?

What does the acromion provide attachements for?

Provides attachment for deltoid and trapezius

What does the Supraglenoid tubercle provide an origin for?

origin of the long head of biceps brachii

What does the Infraglenoid tubercle provide an origin for?

origin of long head of triceps brachii

What does the Coracoid Process provides attachment for?

attachment for pec minor, coracobrachialis and short of the biceps

Describe the Scapulothoracic Joint. Why it is important. and purpose

• NOT a true synovial joint

• functional articulation between the scapula and the posterior thoracic wall.
  

• Provides stability and mobility of entire shoulder
  

• Purpose:

  • Allows ROM of upper extremity,

  • provides a stable base for glenohumeral joint

  • dissipates forces

List out the motions of the scapula

• Elevation/Depression
  

• Protraction/Retraction
  

• Upward/Downward Rotation
  

• Anterior/Posterior Tilt, Internal/External Rotation (subtle but important)

Describe the muscles used for each type of motion that the scapula can do

Describe the extrinstic and intrinsic muscles acting on the scapula

Extrinsic Muscles Acting on the Scapula (Movers and Stabilizers):

• Trapezius

• Latissimus dorsi

• Rhomboid Major and Minor

• Levator Scapulae

• Serratus Anterior

• Pectoralis Minor
  

Intrinsic Muscles originating from the scapula (Scapulohumeral/Rotator cuff)

• Deltoid

• Teres Major

• Rotator Cuff muscles (SITS)

List out the origin, insertion, innervation and action of Serratus Anterior

• Origin: outer surface of the ribs 1-8/9

• Insertion: Entire medial border of scapula
  (anterior surface)

• Innervation: Long thoracic nerve (C5,C6,C7)

• Actions:

  • Protraction of the scapula:

  • Upward rotation of scapula (upper fibers)

  • holds scapula against thoracic wall

What is scapula winging?

Defect in the Serratus Anterior;

leads to weak protraction and inability to hold scapula to rib cage causing the medial border to protrude

Describe impingement syndrome (of serratus anterior)

• weakness/ dysfunction of Serratus anterior

• reduces upward rotation of scapula → superior displacement of humerus and impingement of rotator cuff tendons under acromion

List out the origin, insertion, innervation and action of Pectoralis Minor

• Origin: Ribs 3-5 (anterior surface)

• Insertion: Coracoid process of scapula

• Innervation: Medial pectoral nerve (C8,T1)

• Actions: Depresses scapula, protracts scapula, downward rotation of scapula, accessory muscle of inspiration

What are intrinsic muscles crucial for?

glenohumeral joint stability and movement

What is the origin, insertion, innervation and action of deltoid

• Origin: Spine of scapula, acromion, lateral clavicle

• Insertion: Deltoid tuberosity of humerus

• Innervation: Axillary nerve (C5,C6)

• Actions: Major abductor of the humerus (all fibers)

  • Anterior fibers(Clavicular): flexion, medial rotation of arm

  • Middle fibers (Acromial): abducts arm

  • Posterior fibers (Spinal): extension, lateral rotation of arm

Describe the biomechanics of abduction of arms? Describe the biomechanics of swinging limbs during walking? How does the deltoid help stabilization during movement of upper limb? How do we clinically test the deltoid’s function?

Abduction: Supraspinatus initiate first 15 degrees of abduction →followed by abduction of deltoid

Swinging:

• anterior part of deltoid: assists the pectoralis major in flexing the arm

• Posterior part of deltoid: assists the latissimus dorsi in extending the arm

Deltoid’s role in stabilization:

• helps stabilize glenohumeral joint → hold head of humerus in glenoid cavity during movements of the upper limb

Clinical:

• the arm is abducted, starting from approximately 15°, against resistance

List out the origin, insertion, innervation and actions of Teres Major

• Origin: Dorsal surface of inferior angle of scapula

• Insertion: Medial lip of intertubercular groove of humerus

• Innervation: Lower subscapular nerve (C5,C6)

• Actions: Extends, Adducts, Medially rotates humerus

What is the SITS muscle crucial for? How are they arranged? Combined function of the SITS?

• Critical for dynamic stability of the glenohumeral joint

Arrangement:

• SITS muscles pass laterally to engulf the head of the humerus

• Tendons attach to greater and lesser tubercles

Function:

• “grasp” and pulls large head of humerus medially, holding it against the smaller glenoid cavity of scapula

• SITS’ Tendons + fibrous layer of capsule → musculotendinous rotator cuff → reinforces the capsule on three sides (anteriorly, superiorly, and posteriorly) → providing active support for the joint

What is the origin, insertion, innervation, and action of the Supraspinatus

• Origin: Supraspinous fossa

• Insertion: Greater tubercle of humerus

• Innervation: Suprascapular nerve (C5,C6)

• Action: Initiates abduction (first 15 degrees) of the arm

What is the origin, insertion, innervation, and action of the Infraspinatus

• Origin: Infraspinous fossa

• Insertion: Greater tubercle of humerus

• Innervation: Suprascapular nerve (C5,C6)

• Action: Primary lateral rotator of humerus

What is the origin, insertion, innervation, and action of the Teres Minor

• Origin: posterior surface of scapula adjacent to lateral
  border of scapula

• Insertion: Greater tubercle of the humerus

• Innervation: Axillary nerve (C5,C6)

• Action: Lateral rotator of the humerus

What is the origin, insertion, innervation, and action of the Subscapularis

• Origin: Subscapular fossa (anterior surface)

• Insertion: Lesser tubercle of humerus

• Innervation: Upper and Lower subscapular nerves (C5,C6,C7)

• Action: Primary medial rotator of humerus

What forms the Suprascapular Forament? What passes through here?

Formation:

• suprascapular notch of scapula + superior transverse scapular ( suprascapular) ligament) → converts notch into a foramen)

• Suprascapular nerve pass through the foramen

• Suprascapular artery and vein pass superior to suprascapular ligament

• ARMY over NAVY

What are the boundaries of the Quadrangular space? What passes through it?

Boundaries

• Inferior margin of teres minor

• Surgical neck of humerus

• Superior margin of teres major

• Lateral margin of long head of triceps brachii

Vessels passing through:

• Axillary nerve

• Posterior circumflex humeral artery and vein

Causes and symptoms of Quadrangular space syndrome

impingement of axillary nerve (hypertrophy of muscles or fibrosis of
muscle edges) → weakness of deltoid muscle; atrophy of teres minor (affects control that the rotator cuff muscles exert on shoulder movement)

What are the boundaries of the Triangular space? What passes through it?

• Boundaries

  • Medial margin of the long head of the triceps brachii

  • Superior margin of the teres major

  • Inferior margin of the teres minor
    

• Structures passing through

  • Circumflex scapular artery and vein

What are the boundaries of the Triangular interval? What passes through it?

Boundary:

• Inferior portion of Teres Major

• Medial Side of humerus

• Lateral side of Triceps Brachii

Structures passing through

• Radial nerve

• Profunda brachii artery (deep artery of the arm) and veins

Describe the route and innervation of Suprascapular nerve

Superior Trunk of Brachial Plexus → Passes posteriolaterally through suprascapular foramen → Posterior Sapular region → Innervates supraspinatus → Pass through spinoglenoid notch (between root of spine and glenoid cavity) → Innervates Infraspinatus

Describe the route and innervation of Axillary Nerve

Posterior cord of Brachial Plexus → exits Axilla via passing through Quadrangular Space → Post. Scapular region → Innervates Deltoid/Teres Minor

• Related to surgical neck of humerus with the posterior circumflex humeral artery
  

• Cutaneous branches (superior lateral cutaneous nerve of the arm) – carries general sensation from skin over inferior part of deltoid muscle

Causes and symptoms of Axillary Nerve Damage?

Axillary nerve damage → atrophy of Deltoid and Teres minor

Causes:

• Surgical neck fracture of humerus

• Anterior shoulder dislocation

• Improper use of crutches

Symptoms:

• Flattened appearance of shoulder

• Loss of sensation over lateral side of proximal arm supplied by superior lateral cutaneous nerve of arm (cutaneous branch of axillary nerve)

Describe the route and supply of Suprascapular artery

• from base of neck as branch of thyrocervical trunk (branch of subclavian artery)
  

• Enters posterior scapular region superior to
  suprascapular foramen
  

• Supply the supraspinatus and infraspinatu

Describe the route and supply of Posterior circumflex humeral artery

• from the third part pf the axillary artery in the axilla.
  

• Leave axilla through quadrangular space with axillary nerve and enter posterior scapular region

Describe the route and supply of Circumflex scapular artery

• branch of subscapular artery from third part of axillary artery
  

• Leaves axilla through triangular space and enter posterior scapular region, pass through the origin of the teres minor muscle and form anastomosis with other arteries

What is Scapular dyskinesis? Common patterns?

• Any alteration in the position or motion of the scapula during static posture or dynamic shoulder movements

Common patterns:

• Inferior angle prominence

  • tight pectoralis minor, weak lower trapezius/serratus anterior

• Medial border prominence:

  • Classic scapular winging (weak serratus anterior/long thoracic nerve)

• Early/Excessive Elevation:

  • Overactive upper trapezius, levator scapulae

• Limited Upward Rotation:

  • tight downward rotators (rhomboids, levator scapulae, pectoralis minor)

  • or weak upward rotators (serratus anterior, upper/lower trapezius)

Describe Shoulder Impingement Syndrome

Scapular dysfunction → scapula fails to rotate upwards and tilt posteriorly → acromion does not move out of the way → leads to compression of the rotator cuff tendons (especially supraspinatus) and bursa under the acromion during overhead movements

In a rotator cuff tear, what muscle is the most commonly ruptured?

Supraspinatus

Who is most commonly affected with degenerative tendonitis?

Elderly people

Describe the consequences of a Nerve Entrapment of the Long Thoracic Nerve?

leads to Serratus anterior palsy and classic scapular winging

Describe the consequences of a Nerve Entrapment of the Dorsal Scapular nerve; how can it be entrapped?

Affects rhomboids and Levator scapulae. Can be entrapped by Scalenes

Describe the consequences of a Nerve Entrapment of the Suprascapular nerve

Nerve compression via ligament or muscle as it passes through the suprascapular foramen → affecting
supraspinatus/infraspinatus → difficulty initiating abduction and
weak lateral rotation of the arm

Describe how the brachial plexus could be entrapped?

can be compressed by tight pectoralis minor in Thoracic Outlet Syndrome