Unit 4.1 The Elbow

What are the 4 joints of the shoulder complex?

Sternoclavicular, Acromioclavicular, Scapulothoracic, and Glenohumeral joints.

Why is the shoulder girdle an "open" mechanical system?

The right and left sides are not directly attached, allowing them to move independently.

Which joint is a "physiological" articulation with no bone-to-bone connection?

The Scapulothoracic joint.

What is the ratio of glenohumeral to scapular movement in Scapulohumeral Rhythm?

A 2

How much does the Labrum increase the contact area of the glenoid fossa?

It increases the contact area by 75%.

What are the four Rotator Cuff muscles (SITS)?

Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis.

Which rotator cuff muscle is the primary internal rotator?

The Subscapularis.

Which rotator cuff muscles are the primary external rotators?

Infraspinatus and Teres Minor.

Which shoulder movement is the strongest?

Adduction.

Which shoulder movement is the weakest?

External Rotation.

What is the clinical name for a shoulder "separation"?

Acromioclavicular (AC) joint injury.

What is the most common direction for a shoulder dislocation?

Anterior-Inferior (95% of cases).

What deformity is caused by a rupture of the long head of the biceps tendon?

A "Popeye" deformity.

Which rotator cuff muscle is most commonly torn?

The Supraspinatus.

What is a SLAP lesion?

A tear of the Superior Labrum from Anterior to Posterior.

What is the primary requirement for a standard Total Shoulder Arthroplasty (TSA)?

An intact and functional rotator cuff.

In a Reverse Total Shoulder Arthroplasty (rTSA), where is the ball attached?

The ball is attached to the glenoid fossa (scapula).

When is a Reverse Total Shoulder Arthroplasty (rTSA) indicated?

For massive, irreparable rotator cuff tears.

Why is a posterior Sternoclavicular (SC) dislocation dangerous?

It can displace toward the midline and threaten the airway or major blood vessels.

What are the two theories for Rotator Cuff Impingement?

Mechanical (narrow subacromial space) and Vascular (repeated stretching/weakness).