Intro of shoulder complex

• 4 articulations (sternum, clavicle, ribs, scapula, and humerus
• Has high amounts of mobility = low stability
• Almost no single muscle works in isolation; all work in teams = produce coordinated movement (synergies)

Osteology: BONES

• sternum
• clavicle
• scapula
• (proximal) humerus

Sternum

• Features:
  1. manubrium
  2. clavicular facets
  3. costal facets
  4. jugular notch

Clavicle (posterior/back view)

1. shaft
2. sternal end
3. costal facet
4. costal tuberosity
5. acromial end
6. acromial facet
7. conoid tubercle
8. trapezoid line

Both shoulders view (with angles)

• 20 degrees = clavicle
• 30-40 degrees = scapular plane
• 30 degrees = humeral head retroversion to mid-lateral axis at the elbow

Glenoid Fossa

• space between scapula and humerus head

Coracoid Process w/ scapula

• attachment points for muscles and ligaments
• projects out sharply like crows beak

coracoid process (superior view)

Proximal to humerus

Proximal-to-mid Humerus: Retroversion

Clinical Application: Retroversion

Loss of IR in pitching arm is okay, as long as Total ROM is equal bil

Proxima-to-humerus: With muscles

The major sandwich

Antrology

• the study of anatomy, function, dysfunction and treatment of joints and articulations => JOINT SURFACES
  • Sternoclavicular, arcomioclavicular, glenohumeral, scapulothoracic (physiologic)
• ROLL-SLIDE MECHANICS

Scapulothoracic Movements: Different types

1. Elevation and depression
2. Protraction and retraction
3. upward and downward rotation

Scapualr movements: key things to know

• multiple joints working together = ST movements
• Goal: keep humeral head in as much contact with the glenoid as possible!!

Scapular joint

• ONLY attachment of shoulder complex to axial skeleton = very robust
• LARGE ROM
• How?
  • extensive connective tissue
  • saddle joint

#Sternoclavicular joints (anterior of capsule and ligament section)

SC osteokinematics

• elevation+depression
• protraction+retraction
• posterior clavicular rotation

SC arthrokinematics

1. Elevation (Roll Up // Slide down) = convex+concave
2. Depression (Roll down // slide up) = convex+concave
3. Retraction (Roll and Slide Up)

Acromioclavical joint: what behavior?

• A gliding or plane joint
• NO role-slide arthrokinematics

AC Joint Osteokinematics

• NO ROLL-SLIDE mechanics
• Rotation
  • UP/DOWN and Internal/External

Scapulothoracic "joint" kinematics

• Posterior view
  • elevation (SC joint)
  • downward rotation (AC joint)
• Superior view
  • protraction (SC joint)
  • internal rotation (AC joint)

Acromioclavicular Joint

A gliding or a plane joint => NO roll-slide arthrokinematics

Acromioclavicular joint with ligaments

AC Joint Osteokinematics

• NO ROLL SLIDE
• Upward/Downward rotation
• Internal/External rotation
• Anterior/Posterior tilting

Scapulothoracic “joint” kinematics: Protraction (hunch shoulders)

• Protraction(SC joint) + internal rotation (AC joint)

Scapulothoracic “joint” kinematics: Upward rotation (raise shoulders)

• elevation (SC joint) + downward rotation (AC joint)

#Scapulothoracic “joint” kinematics: Elevation (raise arm up)

• upward elevation (SC joint) + upward rotation (AC joint)

Glenohumeral Joint

• Glenohumeral (GH) + ST = large AROM
• glenoid is directed anterolaterally in the plane of the scapula and with upward inclination
  • => to keep humerus in as much contact as possible

#Glenohumeral Joint: Fibrous capsule

• GHJ is surrounded by a fibrous capsule
• volume of capsule = 2x the side of the humeral head( Axillary pouch =large ROM)
• fibrous capsule is thin, = reinforced by thicker external ligaments
  • stability of the GHJ is not from passive structures = from active ones (muscles)

Additional Stability from Muscles & Labrum

Anterior view of arm

#GH Joint stability (slight incline)

• slight incline of glenoid "locks" the joint
• passive tension of superior capsular structure (CSC) to combat gravity (G) and yield compression force (CF)

GH Osteokinematics

• EXT/FLX
• I.Rotation + Ex. Rotation
• Abbduction+Adduction

GH Arthrokinematics: Flexion/Extension

• SPIN + UP FLEXION

GH Arthrokinematics: Abduction

• UP ROLL + DOWN SLIDE + UP Abduction
• convex on concave

GH Arthrokinematics: ER/IR

• ROLL UP + SLIDE DOWN + EXTERNAL ROTATION UP
• convex on concave

The Six Kinematic Principles 1

• scapulohumeral rhythm = active simultaneous of 180 degrees
  • HOW: simultaneous 120 degrees of glenohumeral (GH) joint abduction
  • HOW: 60 degrees scapulothoracic upward rotation

The Six Kinematic Principles 2

• 60 degrees of upward rotation of scapula during full shoulder abduction
  • simultaneous

The Six Kinematic Principles 3

• the clavicle retracts at the sternoclavicular joint(SC) during shoulder abduction

The Six Kinematic Principles 4

scapular posteriorly tilts & externally rotates (@full shoulder abduction)

The Six Kinematic Principles 5

clavicle posteriorly rotates around OWN axis @shoulder abduction

The Six Kinematic Principles 6

GH joint externally rotates during shoulder abduction

The Six Kinematic Principles: picture

why is the clavicle curvy?

• AC joint party location
  • serratus muscle pulls up = coracoclavicular ligament is pulled tight
    • creates tension + rotates clavicle posteriorly (back) => allows AC joint to full upward rotation

Muscles of the Shoulder Complex: categories

• proximal stabilizers
• distal mobilizers

ST Joint: Elevators Muscles

• Muscle:
  • upper trapezius
  • levator scapulae
  • rhomboids (lesser extent)
• keeps shoulder gridle elevated + upward inclination of glenoid = MORE COMPRESSION FORCE

ST: Depressor Muscles

• Lower Trapezius
• Latissimus Dorsi
• Pec minor
• Subclavius (lesser extent)

When scapular depression is “blocked”

• force from the depressor msucels raise the thorax RELATIVE to fixed scapula and ulna
• lower traps+lats elevate up => pelvic trunk segment moves to fixed scapula arm segment

ST: Protraction

• muscle
  • serratus anterior

ST: Retractors

• Muscles:
  • Middle Trapezius
  • Rhomboids
  • Lower trap

Upper Extremity: Elevation

• “Elevation” of the UE requires:
  • Elevation of the GH joint
  • Upward rotation of the ST joint
  • Dynamic stability/control of arthrokinematics of the GHJ (via the rotator cuff)

GH Joint: Elevators muscles

GH Joint: Elevators muscles

ABDUCTION

• Anterior Deltoid
• Middle Deltoid
• Supraspinatus

GH Joint: Elevators muscles

FLEXION

• Anterior deltoid
• Coracobrachialis
• Long head of biceps brachii

Glenohumeral joints muscles flexion

biceps flexion GHJ

ST: Upward rotators & synergy!

• Muscles:
  • Serratus anterior
  • Upper Trapezius
  • Lower Trapezius

GH and rotator cuff

• GH is loose = high mobility
• rotator cuff controls motion of the humeral head

The Rotator Cuff muscles

• Supraspinatus
• Subscapularis
• Infraspinatus
• Teres Minor

Shoulder: Adduction & Extension

• (sternocostal portion) Pectoralis major*
• Latissimus dorsi*
• Teres major*
• Posterior deltoid
• Long head of triceps brachii

Shoulder: IR (internal rotation)

• MORE MUSCLE MASS THAN ER
• SALT P
• Subscapularis
• Anterior deltoid
• Latissimus dorsi
• Teres Major
• Pectoralis Major

Shoulder: ER (external rotation)

• Infraspinatus
• Teres Minor
• Posterior Deltoid

Muscle for scapula thoracic protraction

Serratus anterior