1121: (Ch 9) Shoulder Girdle

clavicle

"S" shaped bone that connects the upper extremity to the axial skeleton at the sternoclavicular joint.

glenohumeral joint

(b) Ball and socket Joint. A mobile but unstable joint. Features: 1.) Spherical Head of Humerus. 2.) Shallow Glenoid Fossa of Scapula. 3.) Deepened by Glenoid Labrum.

scapular upward rotation

- (Lateral) Tilts glenoid fossa upward. Inferior angle is used as the reference landmark. - The inferior angle of the scapula rotates up and away from the vertebral column.

scapular downward rotation

- (Medial) Tilts glenoid fossa back downward. Inferior angle is used as the reference landmark. - The scapula returns to the resting position. It does not move past the anatomical position.

sternoclavicular ligament

- *Connects the clavicle to the sternum* on both the anterior and posterior surfaces. Therefore there is an anterior sternoclavicular ligament and a posterior sternoclavicular ligament. - These ligaments *limit anterior-posterior movement of the clavicles medial end*. The posterior SC ligament limits anterior motion; the anterior SC ligament limits posterior motion. They both reinforce the joint capsule.

tipping

- Accessory motion. - Maintains contact with trunk. Occurs about a M/L axis. -Some of this motion is normal.

scapular winging

- Accessory motion. - Maintains trunk contact. Occurs about a vertical axis. - Is the posterior lateral movement of the vertebral border of the scapula in the transverse plane. - The vertebral border moves away from the rib cage (miss America wave). -Some of this motion is normal.

Explain reverse action of scapular depressors.

- Arm and shoulder stabilized (on arms of chair or on seat of chair or treatment table). - Scapular depressors pull trunk upward toward scapula and arm. - Trunk moves upward between fixed arms and shoulders.

What are the scapular depressors?

- By direct attachment to scapula: 1.) Lower fibers of trapezius. 2.) Pectoralis minor. - And indirectly by attachment to humerus: 1.) Latissimus dorsi. 2.) Lower fibers of pectoralis major.

What is excessive tipping caused by?

- Caused by weakness of stabilizers of scapula. - Excessive tipping: inferior angle moves away from trunk.

acromioclavicular (AC) joint

- Connects the acromion process of the scapula and the lateral (acromial) end of the clavicle.

coracoacromial ligament

- Does not cross the AC joint but forms a roof over the head of the humerus providing *protection and support to the head of the humerus*. - It attaches laterally on the superior coracoid process and up and out to the inferior surface of the acromion process.

reverse muscle action

- During movement the insertion moves toward the origin. If the insertion is stabilized the origin will move. - It allows the shoulder muscles to have accessory or assistive roles in other joints, primarily of the head and neck.

Give an example of scapular depression.

- Example: wheelchair push-up. - Depressor muscle activity needed if an external force is trying to elevate the scapula and one is trying to resist or overcome this external force.

sternoclavicular (SC) joint

- Formed by the articulation between the manubrium of the sternum and the medial (sternal) end of the clavicle. - Provides the shoulder girdle with its only direct attachment to the trunk.

costoclavicular ligament

- Is short flat rhomboid shaped ligament that *connects the inferior clavicle to the superior surface of the costal cartilage of the first rib*. - Its function is to *limit the amount of clavicle elevation*.

scapulothoracic rhythm

- Is the movement relationship between the shoulder girdle and the shoulder joint. - Increases ROM. - Increases joint stability. *Remember:* - Scapular upward rotation goes with Flexion & Abduction. - Scapular downward rotation goes with extension & adduction.

What are some characteristics of the SC (sternoclavicular) joint?

- It is a synovial joint so it has a joint capsule. - It has 3 major ligaments and a joint disk. - The joint capsule surrounds the joint and is reinforced by the anterior and posterior sternoclavicular ligaments. - The disk serves as a shock absorber. It attaches to the clavicle and manubrium. - Dislocation of the SC joint is rare due to the support by the disks and ligaments.

What kind of joint is the AC joint?

- It is a synovial joint that allows gliding motion to occur allowing movement in 3 planes.

interclavicular ligament

- Located on top of the manubrium *connecting the superior sternal ends of the clavicles. Its function is to limit the amount of clavicular depression*.

What happens when the serratus anterior is weak?

- Medial border of scapula tends to tilt or wing away from thorax. - Results in excessive winging and/or tipping of scapula during shoulder flexion activities.

scapulothoracic articulation

- Not a true joint because no direct contact between bones, and there is no joint capsule. - Consists of a slightly concave anterior surface of the scapula resting on the convex posterior aspect of the rib cage. - Its stability comes form the trunk through the clavicle and surrounding muscles. - It provides necessary normal function of the scapula.

scapular tilt

- Occurs when the shoulder is in hyperextension. - The superior end of the scapula tilts anterior and the inferior angle tilts posteriorly.

What are the force couples producing downward rotation of the scapula?

- Pec minor pulls down, levator scapulae pulls up and the rhomboid pulls in. - *The net effect is scapular downward rotation.*

coracoclavicular ligament

- Provides stability to the AC joint but is not directly located at the joint. It *allows the scapula to be suspended from the clavicle*. - It *connects the scapula to the clavicle* by attaching to the inferior surface of the clavicle's lateral end and to the superior surface of the scapula's coracoid process. - It is divided *into 2 portions: a lateral trapezoid portion and the deeper medial conoid portion. Together they prevent backward motion of the scapula and the limit scapula rotation. Helps prevent AC separation*.

Explain crutch walking in regards to reverse muscle action.

- Reverse muscle action with hands bearing weight on crutch handles to prevent scapula and rib cage from depressing. - The pec minor is pulling up on the rib cage while the lower trap pulls up on the vertebral column and pelvis to elevate the body allowing it to swing through the crutches.

protraction

- Scapula moving laterally away from spine. It's a linear motion. - Synonymous with abduction. - Occurs when scapula moves away from the posterior midline.

retraction

- Scapula moving medially toward spine. It's a linear motion. - Synonymous with adduction. - Occurs when scapula moves toward the posterior midline.

Explain companion motions of the shoulder joint and the shoulder girdle.

- Shoulder joint motions must accompany scapular motions to get full joint movement. - The shoulder girdle and shoulder joint work together to provide full movement. If one is impaired, there will be impaired function at the other.

acromioclavicular ligaments

- Supports the joint by *holding the acromion process to the clavicle*, preventing dislocation of the clavicle. It also reinforces the joint capsule both above and below. - The joint capsule is quite weak despite the support and susceptible to injury during a fall on outstretched hand or a blow to the outside of the shoulder.

What are the motions of the AC joint?

- The AC joint allows subtle movements of the scapula. - Primary motions at the AC joint are upward and downward rotation in the plane of the scapula. - It also contributes to scapular tilting in the sagittal plane and when present scapular winging in the transverse plane.

What are the degrees of movement in shoulder joint motion?

- The first 30 degrees of shoulder joint motion is pure shoulder joint motion. For every 2 degrees of shoulder joint flexion or abduction that occurs, the scapula must upwardly rotate 1 degree (2:1 scapulohumeral rhythm). - Total of 180 degrees of abduction or flexion. - 120 degrees at Glenohumeral, 60 degrees at scapulothoracic.

Where is the scapula located while in resting position?

- The scapula is located between the second and seventh ribs with the vertebral border approx 2-3 inches lateral to the spinous processes of the vertebrae. - The spine of the scapula is approx. level with the spinous processes of T3 and T4 vertebrae.

Give an example of reverse muscle action and explain it.

- The upper trap attaches on the occiput, thus can move the head and neck. When the shoulder is stabilized, bilateral contraction of the upper trap muscles can assist in extending the head. - When the upper trap contracts unilaterally it side bends the head to the ipsilateral side and rotates the neck to the contralateral side. - When the shoulder girdle is stabilized the lower trap and mec miner can reverse their action and assist in elevating the trunk.

What are the force couples of the shoulder girdle?

- The upper trap pulls up, the lower trap pulls down and the lower fibers of the serratus anterior pull horizontally outward. - *The net affect is that the scapula rotates upward.*

What kind of joint is the sternoclavicular joint?

- Tri-axial joint with 3 degrees of freedom. - Described as ball and socket joint; saddle joint. - Motions of this joint are described based on the direction in which the clavicle is moving. The clavicle moves while the sternum remains stationary.

scapula

- Triangle shaped bone on the posterior side of the thorax. - Attaches to the thorax indirectly through its ligamentous attachment to the clavicle. - It is slightly convex anteriorly and glides over the convex posterior rib cage.

elevation

- Upward motion of scapula relative to thorax. It's a linear motion. - Occurs when scapula moves in a superior direction.

What causes excessive winging?

- Usually caused by weakness in the *serratus anterior*. - Excessive motion of this kind brings the medial border away from trunk.

What shoulder girdle motion is occurring while a person is doing push ups? Which muscles are the prime movers? Is this an open chain exercise or closed chain?

1. Scapular protraction and upward rotation. 2. Serratus anterior, Pec minor, upper and lower traps. 3. Closed Chain.

What joint motion occurs when a person exercising pulls a weight up with a straight arm while lying prone on a table? Which muscles are the prime movers? Is this an open chain exercise or closed chain?

1. Scapular retraction. 2. Middle trapezius and Rhomboids. 3. Open Chain.

Recap: What are the motions at the AC joint between the clavicle and acromion of scapula?

1.) *Winging*: Vertical axis; scapula moves around thorax during protraction/retraction. 2.) *Tipping*: M-L axis; scapula moves up or down along thorax during elevation/depression. 3.) *Upward/Downward Rotation*: A-P axis; scapula separates or moves toward clavicle (in frontal plane).

AC separation

1.) 1st degree sprain: the AC ligament is stretched; 2.) 2nd degree sprain: the AC ligament is ruptured and the coracoclavicular ligament is stretched; 3.) 3rd degree sprain: both ligaments are ruptured.

What are the ligaments of the AC joint?

1.) Acromio-clavicular ligaments. 2.) Coraco-clavicular ligament. 3.) Coraco-acromial ligament.

What are the axes of motion of the SC (sternoclavicular ) joint?

1.) Elevation and depression. In the frontal plane, about the AP axis. 2.) Protraction and retraction. In the transverse plane, about the vertical axis. 3.) Upward and downward rotation. In the sagittal plane, about the ML axis.

The sternoclavicular and acromioclavicular joints allow what shoulder girdle motions:?

1.) Elevation. 2.) Depression. 3.) Protraction. 4.) Retraction. 5.) Upward rotation. 6.) Downward rotation.

What motions occur at the glenohumeral joint?

1.) Flexion/Extension. 2.) Abduction/adduction. 3.) Medial and lateral rotation. 4.) Horizontal abduction and adduction. 5.) Triaxial joint - lots of movement..

What does the shoulder complex consist of?

1.) Scapula. 2.) Clavicle. 3.) Sternum. 4.) Humerus. 5.) Rib cage.

What are the joints of the shoulder complex?

1.) Sternoclavicular Joint. 2.) Acromioclavicular Joint. 3.) Glenohumeral Joint. 4.) Scapulothoracic Joint.

What are the three major ligaments of the SC joint?

1.) Sternoclavicular ligament. 2.) Costoclavicular ligament. 3.) Interclavicular ligament.

What are the five muscles responsible for moving the scapula?

1.) Trapezius. 2.) Levator scapula. 3.) Rhomboids. 4.) Serratus Anterior. 5.) Pectoralis minor.

What are the 3 different lines of pull for the trapezius muscle?

3 different lines of pull: upward, inward, downward resulting in 3 different muscle actions.

What is the nerve innervation (N) of the Levator Scapula?

3rd and 4th cervical nerves and dorsal scapular N C5.

Clavicle fractures

Account for the most frequently broken bone in children. Usually result from a fall on the lateral aspect of the shoulder or a FOOSH. The clavicle usually breaks in the midportion.

Which trapezius muscle is the prime mover?

All 3 acting together retract the scapula, but the middle trapezius is the prime mover.

anterior tilt

Anterior movement of superior border of scapular along with posterior movement of inferior border of scapula to maintain scapulothoracic relationship during scapular elevation.

What is the Origin (O) of the Pec Minor?

Anterior surface ribs 3-5

What is the Insertion (I) of the lower trapezius muscle?

Base of scapular spine.

vertebral border of scapula

Between the superior and inferior angles medially; the attachment of the *rhomboid and serratus anterior muscles*.

acromion process of scapula

Broad, flat area on the superior lateral aspect providing attachment for the *upper trapezius muscle*.

What does the glenohumeral joint consist of?

Consists of the scapula and humerus.

What is the Insertion (I) of the Pec Minor?

Coracoid process of the scapula.

depression

D- ownward motion of scapula relative to thorax. It's a linear motion. - Occurs when scapula moves in an inferior direction.

force couples

Defined as muscles pulling in different directions to accomplish the same motion.

What is the nerve innervation (N) of the Rhomboid?

Dorsal scapular N C5.

scapula plane

Due to the curved shape of the rib cage the scapula rests about *30 degrees* anterior to the frontal plane against the posterior thorax.

Explain the motion of the SC joint during shoulder girdle protraction and retraction.

During protraction and retraction, the concave portion of the clavicle slides anteriorly and posteriorly on the convex costal cartilage. The clavicles lateral end moves forward and backward. Motion occurs between the disk and the sternum.

Explain the motion of the SC joint during shoulder girdle elevation and depression.

During shoulder girdle elevation and depression, the convex surface of the clavicle slides inferiorly and superiorly on the concave manubrium as the clavicles lateral end moves up and down. Motion occurs between the clavicle and the disk.

sternum

Flat bone located midline of the anterior thorax.

clavicular elevation

Happens during Scapular elevation or upward rotation.

clavicular depression

Happens during scapular depression or downward rotation

(I) insertion of muscle

Its distal attachment.

(O) origin of muscle

Its proximal attachment.

trapezius muscle

Large diamond shaped muscle divided into 3 parts: 1.) Upper Trapezius. 2.) Middle Trapezius. 3.) Lower Trapezius.

What is the Origin (O) of the Serratus Anterior?

Lateral Surface of the upper 8 ribs.

What is the nerve innervation (N) of the Serratus Anterior?

Long thoracic N (C5, C6, C7).

What is the nerve innervation (N) of the Pec Minor?

Medial Pectoral N C8, T1.

inferior angle of scapula

Most inferior point where vertebral and axillary borders meet.. This point determines scapula rotation.

What is the Origin (O) of the upper trapezius muscle?

Occipital protuberance; nuchal ligament on upper cervical spinous processes.

What is the Insertion (I) of the upper trapezius muscle?

Outer third of the clavicle, acromion process.

posterior tilt

Posterior movement of inferior border of scapula along with anterior movement of inferior border of scapula to maintain scapulothoracic relationship during scapular depression.

coracoid process of scapula

Projection on anterior surface providing attachment for the *pectoralis major muscle*.

spine of scapula

Projection on the posterior surface running from medially to laterally to the acromion process. It provides attachment for the *middle and lower trapezius muscles*.

What are the muscle actions (A) of the lower trapezius muscle?

Scapula depression and upward rotation; assists in scapular retraction.

What are the muscle actions (A) of the Pec Minor?

Scapula depression, protraction, downward rotation and tilt.

What are the muscle actions (A) of the upper trapezius muscle?

Scapula elevation and upward rotation; assists in scapular retraction.

What are the muscle actions (A) of the Levator Scapula?

Scapular elevation and downward rotation; Assists in retraction.

What are the muscle actions (A) of the Serratus Anterior?

Scapular protraction and upward rotation; also keeps the scapula against the rib cage.

What are the muscle actions (A) of the Rhomboid?

Scapular retraction, elevation and downward rotation.

What are the muscle actions (A) of the middle trapezius muscle?

Scapular retraction; (Assists in scapula upward rotation).

What is the Insertion (I) of the middle trapezius muscle?

Scapular spine.

glenoid fossa of scapula

Slightly concave surface that articulates with humerus on superior lateral side above the axillary border and below the acromion process. The fossa is positioned in an anterior, lateral and upward direction.

What is the nerve innervation (N) of the lower trapezius muscle?

Spinal Accessory (CN XI), C3, C4 sensory component.

What is the nerve innervation (N) of the middle trapezius muscle?

Spinal accessory (CN XI), C3 and C4 sensory component.

What is the nerve innervation (N) of the upper trapezius muscle?

Spinal accessory (cranial N XI), C3 and C4 sensory component.

What is the Origin (O) of the middle trapezius muscle?

Spinous Processes of C7 through T3.

What is the Origin (O) of the Rhomboid?

Spinous processed C7-T5.

What is the Origin (O) of the lower trapezius muscle?

Spinous processes of middle and lower thoracic Vertebrae.

superior angle of scapula

Superior medial aspect; provides attachment for *levator scapula muscle*.

Where are the trapezius muscles located?

The Trapezius muscle is the most superior of the posterior shoulder girdle muscles.

axillary border of scapula

The lateral side between the glenoid fossa and inferior angle.

Where is the pec minor located?

The pec minor lies deep to the pec major muscle.

What is the prime mover of the shoulder girdle for *tilt*?

The prime mover muscle is the: *pec minor*.

What are the prime movers of the shoulder girdle for *depression*?

The prime mover muscles are the: *lower trap and pec minor*.

What are the prime movers of the shoulder girdle for *retraction*?

The prime mover muscles are the: *middle trap and rhomboids*.

What are the prime movers of the shoulder girdle for *downward rotation*?

The prime mover muscles are the: *rhomboid, levator scapula, pec minor*.

What are the prime movers of the shoulder girdle for *protraction*?

The prime mover muscles are the: *serratus anterior, and pec minor*.

What are the prime movers of the shoulder girdle for *elavation*?

The prime mover muscles are the: *upper trap, levator scapula, and rhomboid*.

What are the prime movers of the shoulder girdle for *upward rotation*?

The prime mover muscles are the: *upper trap, lower trap, and serratus anterior*.

Where are the rhomboids and levator scapula located?

The rhomboids (E) and levator scapula (D) lie under the trapezius.

Where is the serratus anterior located?

The serratus anterior crosses the lateral chest wall between the latissimus dorsi and the pec major and external obliques.

If the shoulder joint accompanying motion is *extension*, what would the shoulder girdle motion be?

The shoulder girdle motion would be downward rotation and retraction.

If the shoulder joint accompanying motion is *adduction*, what would the shoulder girdle motion be?

The shoulder girdle motion would be downward rotation.

If the shoulder joint accompanying motion is *horizontal adduction*, what would the shoulder girdle motion be?

The shoulder girdle motion would be protraction.

If the shoulder joint accompanying motion is *medial rotation*, what would the shoulder girdle motion be?

The shoulder girdle motion would be protraction.

If the shoulder joint accompanying motion is *horizontal abduction*, what would the shoulder girdle motion be?

The shoulder girdle motion would be retraction.

If the shoulder joint accompanying motion is *lateral rotation*, what would the shoulder girdle motion be?

The shoulder girdle motion would be retraction.

If the shoulder joint accompanying motion is *hyperextension*, what would the shoulder girdle motion be?

The shoulder girdle motion would be scapular tilt.

If the shoulder joint accompanying motion is *flexion*, what would the shoulder girdle motion be?

The shoulder girdle motion would be upward rotation and protraction.

If the shoulder joint accompanying motion is *abduction*, what would the shoulder girdle motion be?

The shoulder girdle motion would be upward rotation.

What is the Origin (O) of the Levator Scapula?

Transverse processes of C1-C4.

What is the Insertion (I) of the Rhomboid?

Vertebral Border of the scapula between the spine and inferior angle.

What is the Insertion (I) of the Levator Scapula?

Vertebral border of scapula between the superior angle and the spine.

What is the Insertion (I) of the Serratus Anterior?

Vertebral border of the scapula, anterior surface.

acromial end of clavicle

attaches laterally to the scapula and provides attachment for the upper trapezius muscle.

sternal end of clavicle

attaches medially to the sternum.

body of sternum

middle 2/3 of the sternum providing attachment for rest of ribs.

superior end of sternum

provides attachment for the clavicle.

manubrium

superior end providing attachment for the clavicle and first rib.

xiphoid process

sword shaped; the inferior tip.