Shoulder Girdle-CH 9 Lenis J. Alicea-Yildirim PT, MEd Revision William B. Young, PT PT 110

Shoulder Complex…clarifications Purpose to allow the hand to be placed in various positions to accomplish tasks. The Shoulder Complex consist of Shoulder girdle + Shoulder joint (glenohumeral joint) Scapula, clavicle, sternum, humerus, rib cage, sternoclavicular joint, acromioclavicular joint, glenohumeral joint and “scapulothoracic articulation” (not a joint). The scapula and the thorax do NOT have a point of fixation…they are connected indirectly by the clavicle and several muscles.

Shoulder Girdle… Term used to discuss the activities of : scapula clavicle sternum (lesser activity) 5 muscles that attach to scapula, clavicle or both to provide motion. The sternoclavicular and acromioclavicular joints allow shoulder girdle motions: Elevation/depression Upward/downward rotation Protraction/Retraction Scapular tilt

Bones and Landmarks… The scapula attaches to the trunk indirectly through its ligamentous attachment to the clavicle. Scapula is slightly concave (anteriorly) Glides over the convex posterior ribcage Resting Position- is located between 2nd- 7th ribs Vertebral body approximately 2-3 inches lateral from the spinous processes of the vertebra. Many muscles also connect the scapula through the trunk

Resting position of the on the scapula on the thorax Flat bone

Scapula... Superior angle Spine Inferior angle Coracoid process Vertebral border Acromion process Axillary border Glenoid fossa

Clavicle… S shape bone=long bone Connects the upper extremity to the axial skeleton Sternal End-Attaches medially to the sternum Body- between the 2 ends Acromial End-attaches laterally to the scapula

Sternum… Is a flat bone Midline of anterior thorax Manubrium (superior end)- attachment for clavicle Body (beneath)- attachment costal cartilages of the ribs Xiphoid process(inferior tip)- “sword shape”

Joint and Ligaments… Sternoclavicular-provides the shoulder girdle with the only direct attachment to the trunk Synovial Joint Double gliding motion Plane shaped 3 planes of motion Basically the clavicle moves while the sternum remains stationary

Sternoclavicular Joint… Synovial Joint Joint capsule 3 major ligaments Costoclavicular Ligament-limits clavicular elevation Interclavicular Ligament-limits clavicular depression A & P Sternoclavicular Ligaments-provides reinforcement to the joint capsule Articular Disk-shock absorber (outstretched hand injuries) Dislocation is rare Unique attachment- contribute to motion in this joint During shoulder elevation/depression- motion between clavicle and disk During protraction and retraction- motion occurs between disk and sternum

Sternoclavicular Joint Ligaments of the sternoclavicular joint (left side cut away to show the disk).

Joint and Ligaments… Sternoclavicular joint Capsular pattern- pain at extreme range Loose packed position- arm resting by side Closed packed position- maximum shoulder elevation

Acromioclavicular joint… It’s a plane shaped synovial joint 3 planes of motion (minimal but important for normal shoulder motion) Joint capsule surrounds the articular borders of the joint Its weak joint and is reinforced above and below superior and inferior (S&I) acromioclavicular ligaments (3)

Acromioclavicular Ligaments… (3) a) S & I Acromioclavicular ligaments- support/by holding the acromion process to the clavicle and prevent dislocation b) Coracoclavicular ligaments-med and lat portions (accessory) Its NOT directly located at the joint Provides stability to this joint Allows scapula to be suspended from the clavicle Its divided into Lateral trapezoid and deeper medial conoid portion Together they prevent backward motion of the scapula Individually they limit the rotation of the scapula c) Coracoacromial Ligament Does NOT cross the acromioclavicular joint Forms an arch over the head of the humerus (makes a roof) Serves as a protective arch/support during upward forces

Ligaments… Ligaments of the Acromioclavicular Joint The coracoacromial ligament forms a roof over the shoulder joint

Joint and Ligaments… Acromioclavicular joint Capsular pattern- pain at extreme range Loose packed position- arm resting by side Closed packed position- 30-90 degrees Shoulder abduction

Joint Motions… Called shoulder girdle or scapular motion e.g. Shoulder girdle protraction/retraction same as scapular abduction/adduction The inferior angle is the point of reference (motion)

Shoulder Girdle Motions Elevation and Depression Protraction and Retraction Upward and Downward Rotation Scapular Tilt “Wind up” or prerelease phase… Shoulder hyperextension pitching swimming bowling

Companion motions of the shoulder… Upward rotation with shoulder flexion and abduction Downward rotation with shoulder extension and adduction Refer to pg 119

Scapulothoracic Rhythm Describes movement relationship between shoulder girdle and shoulder joint. First 30 degrees of shoulder motion is pure shoulder joint motion! After that…for every 2 degrees of shoulder flexion or ABD the scapula must upwardly rotate 1 degree. This is known as 2:1 scapulohumeral rhythm e.g. Try to move the shoulder while holding the axillary border of scapula to prevent rotation…

ANGLE OF PULL Several factors determine the role of a muscle Major Role= Primer Minor Role= Assisting Mover No Role- due to size, angle of pull, possibility of motions or location of muscle to axis Most muscles have a diagonal line of pull Vertical angle of pull…up/down motion horizontal- angle of pull-protracting/retracting Or with more equal horizontal/vertical pull- both motions e.g. Levator Scapula- prime mover in scapula elevation Middle Trapezius- prime mover in retraction of scapula Rhomboids- prime mover in both elevation and retraction

BREAK

Muscles of the Shoulder Girdle… (5) 1. Trapezius a) Upper trapezius b) Middle trapezius c) Lower trapezius 2. Levator Scapula 3. Rhomboids 4. Serratus Anterior 5. Pectoralis Minor

a) Upper Trapezius- (UT) (O) Occipital protuberance and nuchal ligament of upper cervical vertebra (I) lateral end of clavicle and acromion process Line of more vertical than horizontal…is a prime mover in scapular elevation/upward rotation Only assisting mover in retraction All 3 parts work together (synergists) to retract scapula Upper and lower portions are antagonist during elevation/depression 1.Trapezius Large superficial muscle Diamond Shaped 3 different lines of pull

b) Middle Trapezius- (O) Nuchal Ligament of lower cervical vertebrae and spinous process of C7 and upper thoracic Line of Pull- horizontal Prime mover-retraction Assistive- scapular upward rotation c) Lower Trapezius (O) spinous processes of middle and lower thoracic vertebrae (I) base of scapular spine Line of pull- diagonal (more vertical) Effective with depression and upward rotation

2. Levator Scapula Muscle Cover entirely by trapezius Diagonal line of pull (vertical) Prime mover in Scapula elevation Downward rotation Assisting mover in retraction

3. Rhomboids Major Minor Functionally same actions 2 muscles (but anatomical difficulty to separate) Major Minor Functionally same actions Lies under trapezius, but can be palpated when trapezius is relax Oblique line of pull (horizontal and vertical) Prime movers in retraction and elevation/downwardly rotate scapula

Serratus Anterior Muscle (O) Lateral Surface of upper 8 ribs (I)Vertebral border of scapula/anterior surface Maybe palpated with hand over head (lateral side of thorax) Near horizontal line of pull outward Prime mover scapular protraction Lower fibers effective in upwardly rotating scapula They join the upper and lower trapezius muscles to form a force couple rotating the scapula upward Absence results in “Winging of Scapula”

serratus anterior winging of scapula

Muscles pulling in different direction to accomplish the same motion FORCE COUPLE Muscles pulling in different direction to accomplish the same motion

upward rotation and downward rotation

5.Pectoralis Minor Lies deep to pectoralis major muscle The only shoulder girdle muscle located entirely on the anterior surface (3rd-5th ribs Line of pull downward/mostly vertical Prime mover scapular depression Difficult to see downward rotation due to the muscle position (anterior surface) Causes scapular tilt

Reversal Muscle Action Muscle action of the shoulder girdle have been describe as moving insertion (I) toward the origin (O) This allows some of the shoulder girdle muscles to have assistive roles in other joints Head Neck e.g. UT -on head and neck Stabilized shoulder girdle Assists in head/neck extension and laterally bending it to same side and rotating it to the opposite side.

Muscle Innervations… See table 9-2 and 9-3 Pg. 127 Nerves Cranial Nerve XI Dorsal scapular *Long Thoracic Medial Pectoral