Functional Anatomy for the Shoudler

Functional Anatomy of the Shoulder

1. Glenohumeral (GH) Joint Mechanics

  • The GH joint is a convex-on-concave joint.

    • Does not fully adhere to general rules of rotation and translation.

    • There is evidence of axial rotation and translation of the humerus during elevation, although specifics are debated.

  • Clinically accepted that translation (gliding) must be addressed for full GHJ motion restoration.

  • In cases of rotator cuff weakness and joint instability, excessive superior gliding can occur, possibly leading to subacromial impingement.

2. Scapular and GH Joint Musculature

General Considerations

  • Muscle groups involved are essential for shoulder movements and function in occupational therapy.

    • Reflection on muscle functionalities for purposeful movement of the shoulder.

  • Key Questions:

    • How does each muscle support occupational performance?

    • How do shoulder movements affect the upper extremity function?

Major Muscles Identified

  • Infraspinatus /

  • Teres Minor

  • Teres Major

  • Triceps Brachii

  • Deltoid

  • Trapezius

  • Latissimus Dorsi

  • Thoracolumbar Fascia

  • Splenius Capitis

  • Levator Scapulae

  • Rhomboid Major & Minor

  • Supraspinatus

3. Axioscapular Muscles

3.1 Overview

  • No direct skeletal connection of scapula to skeleton; instead, muscles anchor scapula to vertebral column and rib cage.

  • Key Muscles:

    • Trapezius: Stabilizes and mobilizes scapula.

    • Levator Scapulae: Elevates the scapula.

    • Rhomboids: Elevate and downwardly rotate the scapula.

    • Serratus Anterior: Anchors medial border of scapula.

    • Pectoralis Minor: Stabilizes scapula.

3.2 Trapezius

  • Import: Contributes to stabilization and mobilization of the scapula.

    • Functional Breakdown:

    • Upper Fibers: Elevation and upward rotation of scapula.

    • Middle Fibers: Adduction of scapula.

    • Lower Fibers: Depression and upward rotation of scapula.

    • Activity Examples:

    • Reaching overhead (upper/lower fibers).

    • Rowing (middle fibers).

3.3 Levator Scapulae and Rhomboids

  • Function: Elevate and downwardly rotate the scapula.

    • Counterbalance with muscles that upwardly rotate the scapula.

  • Activity Examples:

    • Shrugging shoulders (Levator Scapulae)

    • Reaching into a back pocket (Rhomboids).

4. Serratus Anterior

  • Anchors the medial border of the scapula.

  • Damage to the long thoracic nerve causes scapular winging (instability).

  • Functions:

    • Abduct and upwardly rotate scapula.

    • Elevate the thorax during forced inhalation.

5. Pectoralis Minor

  • Serves as an anchor at the coracoid process against the rib cage.

  • Functions:

    • Depress, abduct, and downwardly rotate scapula.

    • Assist in elevating thorax for forced inhalation.

6. Clinical Applications

6.1 Clavicular Fracture

  • Functions as a strut; a fracture leads to joint instability and pain in arm movement.

  • Muscle activity post-fracture impacts shoulder positioning.

7. Scapular Movements

7.1 Primary Motions of Scapula

  • Frontal Plane Movements: Elevation, depression, abduction, adduction, upward rotation, downward rotation.

  • Functional Movements Include:

    • Abduction with anterior tilt.

    • Adduction and posterior tilt.

    • Upward rotation with elevation.

    • Downward rotation with depression.

7.2 Scapulohumeral Rhythm

  • The relationship between scapula and humerus movement during elevation.

    • Initial 30° of elevation (scapula stationary); thereafter, 1° scapular upward rotation for every 2° of humeral elevation.

  • Essential for effective shoulder motion and joint clearance.

8. Scapulohumeral Muscles

8.1 Components

  • Includes the Rotator Cuff muscles: Infraspinatus, Teres Minor, Subscapularis, Supraspinatus, and others like Deltoid.

  • Functionally involved in stabilizing humeral head and producing motion during upper extremity activities.

  • Activities impacting rotator cuff involve overhead motions and can relate to injuries from repetitive tasks.

9. Common Pathologies

9.1 Rotator Cuff Injuries

  • Risk increases with age; may result from chronic friction or acute trauma.

  • Commonly affects the supraspinatus.

9.2 Glenohumeral Joint Dislocation

  • Most dislocated joint; usually anteriorly due to forceful external rotation with arm in abduction.

  • Related to labral tears.

9.3 Osteoarthritis

  • Affects mobility due to repetitive use and cumulative injury over time.

  • Adaptive equipment may be necessary.

10. Evaluation and Treatment Considerations for Occupational Therapy

  • Assess upper extremity mechanics and muscle imbalances through goniometry and muscle testing.

  • Address dysfunctional posture patterns, particularly with workstation ergonomics.

  • Consider specific occupational needs for individualized interventions.

11. Case Study: Taylor Schultz

11.1 Background

  • Complaint of shoulder pain affecting daily activities, including driving.

  • Observed rounded shoulder posture, impacting scapular positioning.

11.2 Evaluation Considerations

  • Evaluate pain sources, range of motion, and muscle strength.

  • Consider condition of surrounding soft tissues and musculature dynamics.

  • Educate on posture and ergonomic functioning to reduce symptoms.