FUNCTIONAL ANATOMY OF THE SHOULDER AND UPPER ARM

UNIT 2: PSE4U

OBJECTIVES

Identify and discuss the role of each of the following components of the shoulder Bony anatomy Joint articulations Static stabilizers Dynamic stabilizers

Identify and discuss common acute and chronic injuries associated with the shoulder

Bony Anatomy

Joint Articulations

Glenohumeral joint

Acromioclavicular joint

Sternoclavicular joint

Scapulothoracic joint (not shown)

Important Bony Landmarks

Acromioclavicular Joint (AC joint)

a gliding joint within the shoulder. This joint is specific to primates and humans, allowing for the ability to raise the arm above the head. This joint functions as a pivot point, acting like a strut to help with movement of the scapula resulting in a greater degree of arm rotation. Also, the AV joint allows for the transmission of force from the upper arm to the rest of the skeleton

Sternoclavicular Joint

The only true joint attaching the upper extremity to the axial skeleton

Clavicle1st Rib Sternu

m

Sternoclavicular Ligament

Costoclavicular Ligament

The Shoulder = glenohumeral jt

The glenohumeral joint is a ball-and-socket joint that allows for the arm to move in a circular rotation as well as movement of the arm towards and away from the body. The motion that the glenohumeral joint provides is flexion, extension, abduction and adduction.

Static Stabilizers (ligaments)

Glenohumeral joint capsule Acromioclavicular Coracoclavicular Coracoacromial

Superior, Middle and Inferior Glenohumeral Ligament

Coracoclavicular. l Acromioclavicular. l

Coraco-acromial Lig.

Dynamic Stabilizers:Muscles of the Rotator Cuff

Remember: S

(subscapularis) I

(infraspinatus) T (teres

minor) S

(supraspinatus)

Supporting Muscles of the GHJ

Pectoralis Major

Long Head of Biceps

Deltoid

Role of the Rotator Cuff

Hold the head of the humerus in the small and shallow glenoid fossa of the scapula. During elevation of the arm, the rotator cuff compresses the glenohumeral joint in order to allow the large deltoid muscle to further elevate the arm. In other words, without the rotator cuff, the humeral head would ride up partially out of the glenoid fossa and the efficiency of the deltoid muscle would be much less.

Elevation

Depression

AbductionAdduction

Upward

Rotatio

nDownwardRotation

Movements of the Pectoral Girdle

Innervation

Shoulder girdle muscles primarily innervated by cervical & brachial plexus

From Seeley RR, Stephens TD, Tate P: Anatomy and physiology, ed 6, Dubuque, IA, 2003, McGraw-Hill

Injuries to the Rotator Cuff

Acute Tear (fall)

Chronic Tendonitis

(overuse) Impingement ▪ To pinch –supraspinatus gets

pinched between the humerus and the acromion and/or the coracoacromial ligament.

Shoulder Dislocation

Dislocation occurs when a bone is displaced from its original location

Usually involves damage to the joint capsule and the ligaments that hold the joint together

Signs and symptoms include: Joint looks awkward or deformed Joint is painful Joint is not useable

HEALTHY SHOULDERDISLOCATED SHOULDER

TYPES OF DISLOCATIONS

Anterior (85%)

Inferior (5%)

Posterior (10%)

Subcoracoid Dislocation

ANTERIOR DISLOCATION

Arm in abduction and external rotation. Force is taken on the hand or arm which increases the external rotation of the arm causing the head of the humerus to dislocate.

INFERIOR DISLOCATION

Arm is in excessive abduction and a force is taken on the hand pushing the head of the humerus inferiorly out of the glenoid.

Subcoracoid Dislocation

Subcoracoid Dislocation

Anterior Dislocation

POSTERIOR DISLOCATION

The arm is in flexion and adduction. Force is taken on the hand, causing the head of the humerus to be push out the glenoid posteriorly.

POSTERIOR DISLOCATION

The coracoid process may be prominent. The elbow will be at the side and the hand on the stomach. Attempting to turn the arm out causes shoulder pain.

For any dislocated shoulder, do not try to reduce the joint. Do not pull on the arm.

Try to immobilize as best you can (difficult).

Medical referral!

Shoulder Separation

Separation: occurs when bones held together by fibrous ligaments tear and separate from each other.

There are several grades of separation depending on the severity of the torn ligaments

Grades of Shoulder Separation

HEALTHY SHOULDER SEPARATED SHOULDER

YIKES!!