Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Overview

The coracobrachialis, brachialis, and brachioradialis are commonly confused due to:

• Similar-sounding names

• Their role in flexion movements

• Their location along the anterior aspect of the upper limb

Simple Memory Tip

Think in proximal – distal order:

1. Coracobrachialis – Shoulder (proximal)

2. Brachialis – Arm (mid-region)

3. Brachioradialis – Forearm (distal)

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1. Coracobrachialis

Origin

• Coracoid process of the scapula

Shared Origin

• Short head of biceps brachii

• Together form the conjoint tendon

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Insertion

• Middle third of the medial surface of the humeral shaft

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Nerve Supply

• Musculocutaneous nerve

Key Anatomical Feature

• The musculocutaneous nerve pierces the coracobrachialis muscle

• Typically occurs 3–8 cm distal to the coracoid process

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Functions

• Shoulder flexion

• Adduction of the arm

• Stabilization of the glenohumeral joint

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Surgical Importance

• The musculocutaneous nerve passes through this muscle

• At risk during:

  • Anterior shoulder approaches

  • Coracoid exposure

 Retraction of the conjoint tendon may result in nerve injury

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Clinical Correlation

Injury to the musculocutaneous nerve leads to:

• Weak elbow flexion

• Sensory loss over the lateral forearm

Reason

• Terminal branch: Lateral antebrachial cutaneous nerve

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2. Brachialis

Origin

• Distal half of the anterior surface of the humerus

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Insertion

• Coronoid process of ulna

• Ulnar tuberosity

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Nerve Supply

Unique Feature: Dual Innervation

• Musculocutaneous nerve

• Radial nerve

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Function

• Primary flexor of the elbow

Key Point

• Acts in all forearm positions (pronation and supination)

• Unlike biceps, its function is independent of forearm rotation

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Surgical Importance

• During anterior approach to the humeral shaft:

  • The brachialis is split along its nerve supply plane

Advantage

• Protects:

  • Musculocutaneous nerve

  • Radial nerve

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3. Brachioradialis

Origin

• Proximal two-thirds of the lateral supracondylar ridge of humerus

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Insertion

• Lateral surface of the distal radius

• Near the radial styloid process

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Nerve Supply

• Radial nerve

Key Concept

• Although a flexor, it is supplied by an extensor compartment nerve

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Function

• Strong elbow flexor

• Most effective in mid-pronation (neutral position)

Example

• Handshake position

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Clinical Importance

1. Indicator of Radial Nerve Recovery

• First muscle to regain function in radial nerve palsy

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2. Surgical Landmark

• Radial nerve can be accessed between:

  • Brachialis

  • Brachioradialis

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3. Relation to Superficial Radial Nerve

• The superficial branch:

  • Runs beneath brachioradialis

  • Lies lateral to the radial artery

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Clinical Condition: Wartenberg Syndrome

Cause

• Compression of the superficial radial nerve

Symptoms

• Pain over the radial side of the wrist

• Sensory disturbance over the dorsolateral hand

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Comparison Table

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Key Exam Pearls

Coracobrachialis

• Musculocutaneous nerve pierces the muscle

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Brachialis

• Main elbow flexor

• Demonstrates dual innervation

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Brachioradialis

• Flexor supplied by the radial nerve

• First muscle tested in radial nerve palsy