@!EXAM #1: Biomechanics Shoulder Pt.1 Flashcards

• 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)

• sternum
• clavicle
• scapula
• (proximal) humerus

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

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

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

• space between scapula and humerus head

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

• 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)

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

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

• SPIN + UP FLEXION

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

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

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

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

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

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

clavicle posteriorly rotates around OWN axis @shoulder abduction

GH joint externally rotates during shoulder abduction

• 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

• proximal stabilizers
• distal mobilizers

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

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

• 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

• muscle
  • serratus anterior

• Muscles:
  • Middle Trapezius
  • Rhomboids
  • Lower trap

• “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)

• Anterior Deltoid
• Middle Deltoid
• Supraspinatus

• Anterior deltoid
• Coracobrachialis
• Long head of biceps brachii

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

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

• Supraspinatus
• Subscapularis
• Infraspinatus
• Teres Minor

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

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

• Infraspinatus
• Teres Minor
• Posterior Deltoid

Serratus anterior