Courtesy: Dr Jean Jose MD, Associate Chief, Musculoskeletal Radiology Section, Associate Professor of Clinical Radiology, University of Miami School of Medicine, Florida, USA

 

MRI Anatomy of the Shoulder

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Overview

The shoulder is a highly mobile and complex joint composed of:

• Scapula
• Clavicle
• Humerus

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Clinical Importance

Understanding shoulder MRI anatomy is essential for evaluating:

• Rotator cuff pathology
• Labral injuries
• Ligament injuries
• Neurovascular compression

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Key Concept

• Provides wide range of motion
• Stability maintained by soft tissues

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Basic Osteology

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Scapula

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General Features

• Flat triangular bone
• Located on posterior thoracic wall

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Important Parts

Body

• Main flat portion

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Fossae

• Subscapular fossa (anterior)
• Supraspinous fossa (above spine)
• Infraspinous fossa (below spine)

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Borders

• Medial (vertebral) border
• Lateral (axillary) border

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Angles

• Superior angle
• Inferior angle

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Lateral Structures

• Scapular neck
• Glenoid cavity
• Coracoid process
• Suprascapular notch

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Posterior Structures

• Spine of scapula
• Acromion process

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Joint

• Acromioclavicular joint

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Important Scapular Notches

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Suprascapular Notch

• Transmits:
  • Suprascapular nerve
  • Artery

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Spinoglenoid Notch

• Associated with:
  • Suprascapular nerve

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Proximal Humerus Anatomy

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Greater Tuberosity

• Attachments:
  • Supraspinatus
  • Infraspinatus
  • Teres minor

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Lesser Tuberosity

• Attachment:
  • Subscapularis

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Bicipital Groove

• Contains:
  • Long head of biceps tendon

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Neck

• Anatomical neck
• Surgical neck

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Glenoid Labrum

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Definition

• Fibrocartilaginous rim around glenoid

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Function

• Deepens socket
• Enhances stability

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Regions

• Superior
• Inferior
• Anterior
• Posterior

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Rotator Cuff

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Muscles

• Supraspinatus
• Infraspinatus
• Teres minor
• Subscapularis

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Function

• Stabilizes glenohumeral joint

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Tendon Insertions

• Supraspinatus – superior facet
• Infraspinatus – middle facet
• Teres minor – inferior facet
• Subscapularis – lesser tuberosity

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Important Shoulder Spaces

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Triangular Space

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Boundaries

• Superior: Teres minor
• Inferior: Teres major
• Lateral: Long head of triceps

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Contents

• Circumflex scapular vessels

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Triangular Interval

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Boundaries

• Superior: Teres major
• Medial: Long head of triceps
• Lateral: Lateral head of triceps

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Contents

• Radial nerve
• Profunda brachii artery

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Quadrangular Space

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Boundaries

• Superior: Teres minor
• Inferior: Teres major
• Medial: Long head of triceps
• Lateral: Surgical neck

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Contents

• Axillary nerve
• Posterior circumflex humeral artery

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Anterior Shoulder Muscles

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Pectoralis Major

• Parts:
  • Clavicular
  • Sternal
  • Abdominal

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Insertion

• Lateral lip of bicipital groove

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Deltoid Muscle

• Parts:
  • Anterior
  • Middle
  • Posterior

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Function

• Abduction and stabilization

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Other Muscles

• Pectoralis minor
• Subclavius

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Coracoid Process Attachments

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Muscles

• Pectoralis minor
• Coracobrachialis
• Short head of biceps

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Deltopectoral Groove

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Location

• Between deltoid and pectoralis major

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Contents

• Cephalic vein
• Thoracoacromial artery

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Shoulder Ligaments

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Coracoclavicular Ligaments

• Conoid (medial)
• Trapezoid (lateral)

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Acromioclavicular Ligaments

• Superior
• Inferior

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Coracoacromial Ligament

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Function

• Forms coracoacromial arch

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Clinical Importance

• Thickening — impingement syndrome

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Glenohumeral Ligaments

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Types

• Superior
• Middle
• Inferior

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Inferior Ligament Components

• Anterior band
• Posterior band
• Axillary pouch

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Rotator Cuff Interval

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Location

• Between:
  • Supraspinatus
  • Subscapularis

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Contents

• Long head of biceps
• Coracohumeral ligament
• Superior glenohumeral ligament

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Biceps Pulley System

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Function

• Stabilizes long head of biceps tendon

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Components

• Coracohumeral ligament
• Superior glenohumeral ligament

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Neurovascular Structures

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Suprascapular Nerve

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Course

• Through suprascapular notch — spinoglenoid notch

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Clinical Importance

• Lesion at notch:
  • Affects supraspinatus + infraspinatus
• Lesion at spinoglenoid:
  • Affects infraspinatus only

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Axillary Nerve

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Course

• Passes through quadrangular space

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Accompanied by

• Posterior circumflex humeral artery

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Summary

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Key Structures

• Bones:
  • Scapula, clavicle, humerus
• Rotator cuff muscles
• Glenoid labrum
• Shoulder ligaments
• Neurovascular structures

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Key Concepts

• Stability mainly from soft tissues
• Rotator cuff is critical stabilizer
• Important spaces:
  • Triangular space
  • Quadrangular space
  • Triangular interval