Shoulder Girdle: Chapter 4

• The Shoulder Girdle is covered in Chapter 4.

Announcements

• Further reading can be found at http://www.reachutmost.com/2017/03/17/protraction-retraction-on-and-other-movements-of-the-scapula/.
• More information can be found at https://www.youtube.com/watch?v=D3GVKjeY1FM.

Hints for Exams

• You are not responsible for learning the nerves.
• The Innervation section within each muscle section will be emphasized.
• Ligaments will generally not be emphasized
• Palpation should be practiced on yourself or a friend.

The Shoulder Girdle

• The shoulder girdle includes the scapula-clavicle-sternum.
• The shoulder girdle supports the base for upper extremity movement.
• The scapula is the upper extremity attachment point.
• The scapula and clavicle move as a unit.

Bones (Key Bony Landmarks)

• Scapula
• Coracoid process
• Acromion process
• Spine
• Glenoid fossa
• Lateral border
• Medial border
• Inferior angle

Joints

• Sternoclavicular
• Acromioclavicular
• Scapulothoracic
• Glenohumeral joint is NOT part of the shoulder girdle.

Joints: Sternoclavicular Joint

• Articulation occurs between the sternal end of clavicle with manubrium of sternum
• It has fibrocartilage articular discs.
• It is an Arthrodial (plane) or Sellar (saddle) joint.
• There is slight movement in all 3 planes.
• Movement is more common in sagittal and frontal plane but still has some movement in transverse.
• Movement is not typically voluntary.

Joints: Acromioclavicular Joint

• Articulation occurs between Acromial end of clavicle with acromion process of scapula.
• It is an arthrodial (plane) joint
• It has slight gliding motion between clavicle and scapula during other shoulder motions.
• It is not typically voluntary.
• Important movements include elevation and depression.

Joints: Scapulothoracic Joint

• Is found between the scapula and loose connective tissue between serratus anterior and subscapularis muscles.
• It's a False joint.
• Movement is 3 planes
• It allows for abduction and adduction.
• It helps with upward rotation and downward rotation.
• It supports elevation and depression.
• It moves with the AC and SC joints.
• All 3 joints move- but most obvious are from the scapulothoracic.

Movements

• Common pivot point is at the SC joint
• It has a least movement
• Shoulder girdle movements are easiest to understand as scapular movements
• Anterior view of shoulder girdle

Movements: Abduction/Protraction

• Scapula moves laterally away from the spinal column

Movements: Adduction/Retraction

• Scapula moves medially toward the spinal column

Movements: Upward rotation

• Inferior angle moves superiorly and laterally away from the spinal column

Movements: Downward rotation

• Returning the inferior angle medially and inferiorly toward the spinal column

Movements: Elevation

• Upward or superior movement of the scapula

Movements: Depression

• Downward or inferior movement of the scapula

Synergy with glenohumeral joint

• Shoulder joint and shoulder girdle work together
• Shoulder girdle muscles stabilize the scapula during smaller shoulder joint actions
• Shoulder girdle muscles move scapula to maintain contact between glenoid fossa and head of humerus
• This protects the shoulder joint with proper positioning.
• Without movement of shoulder girdle, could only raise humerus to 90°-100° of shoulder abduction and flexion

Muscles- For Tests

• It is important to know how to identify the muscle by name
• Origin points (more stable)
• Insertion points (more mobile)
• Actions (concentric contraction)
• Concentric contraction: muscle tension developed as muscle shortens
• During concentric contractions, the insertion point generally moves closer to the origin point

Muscles

• Five muscles: Pectoralis minor, Serratus anterior, Trapezius, Rhomboid, and Levator scapulae.
• All originate on axial skeleton and insert on scapula or clavicle
• Do not have actions at shoulder joint (glenohumeral joint)

Muscles: Axial Skeleton

• 5 distinct sections.
• Cervical with 7 vertebrae.
• Thoracic with 12 vertebrae.

Muscles: Trapezius

• Origin: Occipital bone-T12
• Insertion: Lateral 1/3 of clavicle, acromion process, scapular spine
• Action:
• Upper: elevation, upward rotation (weaker)
• Middle: elevation, upward rotation, adduction/retraction (stronger)
• Lower: depression, retraction (weaker)
• Together: upward rotation and retract simultaneously
• Concentric contraction: muscle tension developed as muscle shortens.

Trapezius

• Applications:
• Fixes scapula for deltoid action, works with rhomboids
• Allows arms to be lifted over head (upward rotation)
• Strengthened by shrugs etc..

Muscles: Levator Scapulae

• Named for action
• Origin: Transverse processes of C1-C4
• Insertion: Medial border of scapula
• Action: elevation, weak downward rotation, weak adduction/retraction
• Application: shrugging, extending the neck or flexing laterally (if pectoralis. Minor fixes scapula)
• Site of tightness from chronic tension, carrying a backpack

Muscles: Rhomboid

• Rhomboids (major and minor)
• Origin: Spines of vertebrae C7-T5
• Insertion: Medial border of scapula
• Action: retraction, elevation, downward rotation
• Application: fixes scapula in retraction when muscles of shoulder joint are adducting/extending (posture)
• Strengthened by chin ups, dips, bent over rows

Muscles: Serratus Anterior

• Origin: Ribs 1-9
• Insertion: anterior surface of medial border of scapula
• Actions: abduction/protraction, upward rotation (slight)
• Application: throwing a ball; punching (boxers); push-ups; bench press; overhead press

Muscles: Pectoralis Minor

• Origin: Anterior aspect of ribs 3-5
• Insertion: Coracoid process of scapula
• Action: Depression, downward rotation of the scapula, works together with serratus anterior to give true protraction
• Application: pushing the body upwards; works with serratus anterior in most movements of pushing with the hands

Muscles: Subclavius

• Named for Location
• Origin: 1st rib
• Insertion: Subclavian groove of clavicle (inferior portion of clavicle)
• Action: stabilizes and protects sternoclavicular joint by assisting in moving the clavicle, assists in depression and protraction
• Does not directly move scapula

Muscles: Importance of posture

• Practice good posture
• Maintain appropriate lumbar lordotic curve
• The shoulder girdle should be positioned over pelvis
• It maintains head and cervical spine over trunk
• Eases inspiration

Muscles: Importance of posture

• There is a tendency to develop forward shoulder posture
• Scapula protractors and depressors are stronger than retractors
• It places stress on posterior spinal muscles, glenohumeral