Module 5 - Shoulder Complex

Functional joints

where movement occurs in the shoulder complex

shoulder complex involves:

• sternum

• clavicle

• ribs

• scapula

• humerus

4 functional joints

• scapulothoracic articulation

• sternoclavicular (SC) joint

• acromioclavicular (AC) joint

• glenohumeral (GH) joint

sternoclavicular (SC) joint

• links UE with the axial skeleton; incredibly stable joint

• irregular saddle-shaped synovial joint

acromioclavicular (AC) joint

• transfer force from the scapula to the clavicle

• plane synovial joint

glenohumeral (GH) joint

ball and socket synovial joint

manubrium

upper part (proximal) part of the sternum that articulates with the clavicle at the clavicular facets

jugular notch

superior part of the manubrium between the clavicular facets

clavicle

• s-shaped

• medial third (anteriorly convex)

• lateral third (anteriorly concave)

  • articulates with the scapula (at the acromial facet)

Acromioclavicular (AC) joint surface anatomy

if arm is elevated and shoulder is medially and laterally rotated, clunking/grating may be felt

scapula

flat, triangular shaped bone

3 borders of the scapula

• medial (vertebral) border

• lateral (axillary) border

• superior border

3 angles of the scapula

• inferior angle

• superior angle

• lateral angle

scapula fossae (cavities)

• supraspinatus fossa

• infraspinatus fossa

• subscapular fossa

  • glenoid fossa

scapula prominences

• spine

• acromion

  • coracoid process

humeral head

articulates the scapula at the glenoid fossa

greater tubercle

• prominence on the humerus

  • attachment site for supraspinatus, infraspinatus, and teres minor (lateral)

lesser tubercle

attachment site for subscapularis

deltoid tuberosity

insertion site of deltoid (lateral)

intertubercular (bicipital) groove

• depression on the humerus

• ceiling: transverse humeral ligament (not a true ligament, actually part of the subscapularis tendon)

• center: long head of the biceps

• floor: latissimus dosrsi attachment site

radial groove

path for the radial nerve (humerus)

greater tubercle surface anatomy

immediately inferior to the lateral edge of the acromion with a small gap between the two bony prominences

scapulothoracic (ST) articulation

not a direct joint but a functional joint between the rib cage and scapula separated by muscle tissue (subscapularis and serratus anterior)

-almost all functional activities involve a combo of ST joint motions

ex) pulling a door open: scapula adduction and posterior tilt

scapulothoracic (ST) joint motions

elevation and depression, protraction and retraction, upward and downward motion, accessory motion

Scapulothoracic (ST) joint motion examples

• elevation: shrug

• protraction: punch

• upward rotation: jumping jack

scapular plane (scaption)

plane of motion traveled by the scapula along the rib cage

• protraction: out like pushing a door

• retraction: bringing arm to side (frontal plane) -→ moving up and down

sternoclavicular (SC) joint

links the upper extremity with the axial skeleton ; incredibly stable joint

sternoclavicular (SC) joint stabilizers

• anterior and posterior sternoclavicular joint ligaments

• interclavicular ligament

• costoclavicular ligament

• articular disc

anterior and posterior sternoclavicular joint ligaments

resist anterior/posterior translation

interclavicular ligament

limits excessive depression

costoclavicular ligament

primary resistant to elevation

articular disc

joint stability and shock absorber

sternoclavicular (SC) joint kinematics

• 3 DOF

• frontal plane (sagittal axis): shrugging (~45°) / depression (~10-15°)

• transverse plane (vertical axis): reaching forward and back (protraction (~15°) / retraction (~15°)

• sagittal plane: posterior axial rotation of clavicle (~20-35° during full elevation)

Acromioclavicular (AC) joint stabilizers

• acromioclavicular ligaments

• corcoclavicular (CC) ligaments

acromioclavicular ligaments

provide horizontal stability, preventing the joint from separating front-to-back

coracoclavicular (CC) ligaments

• composed of the conoid and trapezoid ligaments

  • provide primary vertical stability and prevent superior displacement

Acromioclavicular (AC) joint is inherently susceptible to dislocation due to the ____ nature of the articulation

sloped

common mechnism of injury for AC joint

fall on said of the body, sports, car accident

Acriomioclavicular (AC) joint kinematics

• 3 DOF

• frontal plane (sagittal axis): upward rotatuon during abduction (upward/downward rotation)

• transverse plane (vertical axis): internal rotation during scapula protraction (internal/external rotation)

• sagittal plane (frontal axis): anterior tilt during shrugging (anterior/posterior tilting)

Shrugging (elevation) is a combination of what two joints?

SC elevation + AC downward rotation

Protraction (punching forward) is a combination of what two joint motions?

SC protraction + AC internal rotation

Upward rotation “reaching overhead” is a combination of what two joint motions?

SC elevation + AC upward rotation

Glenohumeral (GH) joint

• articulates with the convex head of humerus with the concavity of glenoid fossa

  • ball and socket synovial joint

glenohumeral (GH) joint kinematics

• 3 DOF

• frontal plane (sagittal axis): reaching sideways (Abduction 120° /Adduction ~75°)

• transverse plane (vertical axis): Internal rotation (70-90°) / External rotation (90°)

• Horizontal adduction (130°) / Horizontal abduction

• Sagittal plane (frontal axis): Flexion (120°) / Extension (45-60°) ; e.g. reaching forward

glenohumeral (GH) joint stability

• inherently unstable

  • only 25-30% of the humeral head is in contact with the glenoid fossa

glenohumeral (GH) joint stabilizers

• active stabilizers: rotator cuff muscles

• passive stabilizers: restraint provided by the joint capsule, and tendons

• scapulothoracic posture

  • negative intrascapular pressure

Inferior glenohumeral ligament (IGHL)

• most important stabilizer in abduction against anterior translation

• sling/hammock like

  • injury/laxity leads to recurrent anterior dislocations of the humeral head

Glenoid labrum

• rim of fibrocartilage around the glenoid fossa

• deepens the concavity of the fossa

  • increases surface area contact with the humeral head (~50%)

Long head of biceps _____ from the superior labrum and supraglenoid tubercle

originates

Long head of biceps function

dynamic stabilizer resisting anterior translation in abduction and external rotation

Superior Labrum (SLAP) lesions are them most common injuries in _____ throwing athletes

overhead

coracoacromial arch

forms the “roof” of the GH joint, providing superior stability

subacromial pain syndrome

• presents as pain with ovehead motion (60°-120°)

  • weakness in scapular and rotator cuff muscles

GH joint abduction arthrokinematics

superior roll, inferior glide

arthrokinematics

small-amplitude, involuntary movements (roll, glide, spin) occurring between joint surfaces during voluntary motion

Full abduction requires _____ rotation

external

Scapulohumeral rhythm

describes the coordinated movement between the glenohumeral (GH) joint and the scapulothoracic (ST) articulation during shoulder motion

ratio for glenohumeral (GH) joint: ST joint

2:1

for every 3° of shoulder elevation: 2° ___ joint abduction', 1° _____ joint upward rotation

GH; ST

flexion (shoulder ROM)

• total ROM; 180°

• GH contribution: 120°

• ST contribution: 60°

extension (shoulder ROM)

• total ROM: 60°

• GH contribution: 40°

  • ST contributiom: 20°

abduction (shoulder ROM)

• total ROM: 18°

• GH contribution: 120°

  • ST contribution: 60°

adduction (shoulder ROM)

• Total ROM: 30-50°

• GH contribution: 20-35°

  • ST contribution: 10°-15°

internal rotation (shoulder ROM)

• total ROM: 70°-90°

• GH contribution: 70°-90°

  • ST contribution: 0°

external rotation (shoulder ROM)

• total ROM: 90°

• GH contribution: 90°

  • ST contribution: 0°

adhesive capsulitis

• frozen shoulder

  • common in adults, especially females 40-60 y/o

axioscapular muscles originate on the _____

spine, ribs, cranium

axioscapular muscles insert on the _____

scapula and clavicle

posterior axioscapular muscles

trapezius (upper, middle, lower) levator scapulae, rhomboids

anterior axioscapular muscles

serratus anterior, pectoralis minor, subclavius

axiohumeral muscles

• muscles that link the axial skeleton and humerus directly

• anterior: pectoralis major

  • posterior: latissimus dorsi

trapezius

• elevates, depresses, retracts, and rotates the scapula: rotates arm, extends head and neck

trapezius origin

external occipital protuberance, medial portion of superior nuchal line of the occipital ligamentum nuchae and spinous processes of C7-T12

trapezius insertion

lateral 1/3 of clavicle acromion, and spine of the scapula

ex) reaching for an object overhead, rowing a kayak

upper trapezius

extends and laterally flexes head and neck, scapular elevation and upward rotation

middle trapezius

abducts and stabilizes scapula

levator scapulae

elevates and adducts scapula, downward rotates scapula, rotates and laterally flexes the head and neck

levator scapulae origin

transverse processes of first through fourth cervical vertebrae

levator scapulae insertion

medial border of scapula between superior angle and superior portion of spine of scapula

ex) shrugging shoulders or carrying a briefcase

rhomboids

adducts, elevates, and downwardly rotates scapula

rhomboids major origin

spinous processes of T2-T5

rhomboids minor origin

spinous process of C7-T1

rhomboids major insertion

medial border of the scapula between the spine of the scapula and inferior angle

rhomboid minor insertion

upper portion of medial border of the scapula, across from spine of the scapula

ex) reaching into back pocket

latissimus dorsi

extends, adducts and medially rotates the arm, draws shoulder downward and backward

ex) wheelchair mobility (propelling a manual wheelchair forward), standing from sitting (pushing down on the arms of a chair)

latissisimus dorsi origin

• inferior angle of scapula

• spinous processes of last 6 thoracic vertebrae

• last 3-4 ribs

• thoracolumbar fascia

  • posterior iliac crest

latissimus dorsi insertion

intertubecular groove of the humerus

serratus anterior actions with the origin fixed

• abducts scapula

• upwardly rotates scapula

• depress the scapula

• hold the medial border of the scapula against the ribcage

serratus anterior actions with the scapula fixed

may act to elevate the thorax during forced inhalation

serratus anterior origin

external surface of the upper 8-9 ribs

serratus anterior insertion

anterior surface of medial border of the scapula

ex) pushing a heavy door

pectoralis minor

depresses, abducts, and downwardly rotates the scapula

pectoralis minor origin

third, fourth, and fifth ribs

pectoralis minor insertion

medial surface of coracoid process of the scapula

ex) taking a deep breath, walking with crutches

pectoralis major

adducts shoulder, internally rotates shoulder, elevates the thorax

clavicular fibers of the pectoralis major

flexes shoulder, horizontally adducts shoulder

sternocostal fibers of the pectoralis major

extends shoulder

pectoralis major origin

medial half of the clavicle, sternum, cartilage of first through sixth ribs

pectoralis major insertion

crest of greater tubercle of humerus

ex) reaching across the body into an overhead cabinet, putting on a seatbelt

subclavius

anchors and depresses the clavicle