Lecture on Rotator Cuff and Shoulder Mechanics

Rotator Cuff Muscles

• Comprised of four muscles: Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis
• Mnemonic: SITS
• These muscles surround the humeral head, aiding in shoulder stabilization
• Each muscle contributes differently to shoulder movement

Scaption

• Definition: Movement along the scapular plane (approx. 30° anterior to the frontal plane)
• Scaption involves raising the arm diagonally at about 30° angle
• Commonly used in rehabilitation, especially by Occupational Therapists (OTs)
• Scaption provides a safer movement pattern for shoulder training, particularly for rotator cuff injuries

Shoulder Girdle and Joint Movement

• Combination of shoulder girdle and shoulder joint movements are assessed together
• Evaluation includes checking both the GH joint and the scapula for full range of motion

Examples of Joint and Girdle Collaboration

• Shoulder Flexion: Shoulder girdle assists with upward rotation
• Shoulder Extension: Scapula assists with downward rotation and retraction
• Hyperextension: Scapula tilting occurs

Scapulohumeral Rhythm

• Defines the coordinated movement ratio between the shoulder joint and the shoulder girdle
• Generally accepted ratio: 2:1 (GH joint to scapula)
• Initial 30° of shoulder flexion or abduction involves GH joint only; afterward, scapular muscles engage
• For 180° shoulder abduction: 120° by GH joint, 60° by scapula (30° AC joint, 30° SC joint)
• The ratio is similar for shoulder flexion, though joint contributions differ

Common Shoulder Pathologies

• Bone Fracture: Often seen in stroke patients
• Dislocation: Frequent in stroke patients with hypo or hyper tone
• Impingement Syndrome: Compression between acromion arch and humeral head
• Rotator Cuff Tears: Especially in Supraspinatus due to its role in shoulder abduction
• Biceps Tendonitis: Inflammation of the biceps long head, common due to overuse

Key Points

• The shoulder is highly mobile but also prone to injury
• Understanding the mechanics and common pathologies aids in better assessment and treatment

Conclusion: The lecture provided insights into the structure, mechanics, and common pathologies of the shoulder complex, emphasizing the importance of coordinated movement and the role of various muscles and joints.