Forearm Fractures

Published on 16/04/2015 by admin

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Last modified 22/04/2025

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22 Forearm Fractures

Anatomy of the Forearm

image

Forearm Bones

Ulna

• Parts and landmarks: olecranon, trochlear notch, coronoid process, shaft, anterior border, styloid process
• Cylindrical long bone; olecranon palpable subcutaneously at elbow joint; (medial) styloid process distal
• Bears major forces transmitted across elbow joint

Radius

• Parts and landmarks: head, neck, radial tuberosity, shaft, styloid process, carpal articular fossa, scaphoid fossa, lunate fossa, ulnar notch
• Cylindrical long bone with head in elbow joint; (lateral) styloid process distal
• Radiocarpal joint has articular disc that articulates with carpals and ulnar styloid process.
• Bears major forces transmitted across wrist joint

Elbow Joint

• Compound joint involving humeral-radial, humeral-ulnar, and proximal radioulnar joints

image Medial: trochlea of humerus with trochlear notch of the ulna
image Median: proximal radioulnar joint
image Lateral: capitulum of humerus with head of radius

• Ulnar (medial) collateral ligament: from medial epicondyle of humerus to (1) coronoid process and (2) medial olecranon
• Annular ligament passes around radial neck, stabilizing it via insertions into the ulna
• Lateral (radial) collateral ligament passes from lateral epicondyle (humerus) to annular ligament.
• Large fibrous joint capsule underlies collateral ligaments.
image

Forearm: Serial Cross Sections

Compartments of the Forearm

• External investing antebrachial fascia is relatively tough and nonexpansile, with fascial septa between compartments.
• Proximal forearm

image Anterior (flexors, pronators)

image Median nerve, to all flexors except flexor carpi ulnaris and 2 medial heads of flexor digitorum superficialis (ulnar nerve supplied)
image Anterior interosseus nerve (deep branch median) innervates distal pronator quadratus and flexor pollicis longus.

image Interosseus membrane separates deep anterior and posterior compartments.
image Posterior (extensor): radial nerve > deep radial and posterior interosseus nerves

• Lower forearm: flexor digitorum superficialis and profundus tendons, flexor pollicis longus, pronator quadratus
• Spaces around flexors digitorum tendons and sheaths communicate with hand spaces: pathway for forearm-hand compartment syndrome.
• Dorsal antebrachial spaces communicate with dorsal hand and digit spaces.

Vessels and Nerves

image

Forearm: Arteries and Nerves (Anterior View)

Arterial Supply of the Forearm

• Brachial artery

image Typically divides into main radial and ulnar artery branches in cubital fossa
image Ulnar typically gives rise to common interosseus artery, with its anterior and posterior interosseus branches.

• Anastomoses between upper (collateral) and lower (recurrent) branches preserve blood flow across elbow joint, with both anterior and posterior connections from medial and lateral vessels.
• Lateral anastomoses

image Anterior: radial collateral branch (profunda brachii) with radial recurrent branch (radial)
image Posterior: middle collateral branch (profunda brachii) with recurrent interosseous branch (typically posterior interosseous)

• Medial anastomoses

image Anterior: inferior ulnar collateral (brachial) with anterior ulnar recurrent (ulnar)
image Posterior: superior ulnar collateral (brachial) with posterior ulnar recurrent (ulnar)

• Distally, main radial and ulnar arteries pass through deep anterior forearm laterally and medially (respectively) to enter wrist and palm.

Veins of the Forearm

• Highly interconnected superficial and deep vein networks drain hand and forearm
• Superficial venous network

image Originates in dorsal venous arch of hand
image Cephalic vein: distal, at lateral wrist, runs the length of upper limb to pectoral triangle
image Basilic vein: distal, at medial wrist, runs most of the length of upper limb to arm
image Highly individual patterns of interconnections between cephalic and basilic tributaries

• Deep veins accompany corresponding arteries: valved, arterial counterpulsation effect pumps blood.

image Brachial vein

image Accompanies brachial artery
image Merges with basilic vein to form axillary vein
image Tributaries: ulnar and radial veins accompanying artery branches

Nerves of the Forearm

• Hilton’s law: nerves supplying a joint also innervate muscles acting across it, as well as skin over distal insertions of those muscles

Median Nerve (C6-T1)

• Enters the forearm anteromedially at elbow and passes through pronator teres
• Deep portion, anterior interosseus nerve, travels in neurovascular bundle along interosseus membrane to pronator quadratus.
• Main portion travels along lateral border of flexor digitorum profundus, passing under flexor retinaculum, entering palm via carpal tunnel.
• Neurovascular plane of anterior forearm lies between flexors digitorum superficialis and profundus.

Ulnar Nerve (C7-T1)

• Passes posterior to medial epicondyle of humerus, within the cubital tunnel, to penetrate flexor carpi ulnaris near its origin
• Passes distally in forearm in the neurovascular plane, along medial aspect of flexor digitorum profundus
• Enters the palmar space by passing lateral to the flexor carpi ulnaris tendon and pisiform bone

Radial Nerve (C5-T1)

• Passes anterior to lateral epicondyle of humerus after traversing radial groove of humerus
• Posterior cutaneous nerve of forearm arises proximal to condyle.
• Superficial radial nerve (sensory) travels on surface of supinator, deep to brachioradialis and tendon, and supplies area on dorsum and eminence of thumb and lateral back of hand.
• Main nerve enters posterior compartment of forearm by penetrating supinator.
• Deep radial nerve exits supinator and travels distally as posterior interosseous division.

image Proximal and distal deep branches to distal extensor compartment muscles

Clinical Correlates

Antebrachial Compartment Syndrome

• Distal radius, ulna, or carpal fractures and related tissue and vascular trauma can lead to increased compartment pressure(s), swelling, pain, or paresthesias.
• Anterior (volar) forearm is relatively prone to developing posttraumatic compartment syndrome.
• Causes: fractures of supracondylar humerus, ulna, radius, wrist
image

Elbow Dislocation

Elbow Dislocations

• Often associated with proximal ulna fractures involving coronoid process or olecranon
• Radial head may be involved with coronoid in posterior displacements and fractures: open reduction and fixation is preferred treatment in adults.
image

Fractures of the Ulnar Shaft

image

Fractures of Radial Head and Neck

image

Biomechanics of Forearm Fracture

image

Colles’ Distal Radial Fracture

Ulna and Radius Fractures

• Proximal

image Olecranon: direct trauma or fall onto outstretched hand with triceps contraction
image Radial head: direct trauma or fall with impaction of radial head into capitulum
image Assess neurovascular deficits with history and physical exam.

• Mid-forearm

image Diaphyseal fractures of ulna and radius often occur together, with forearm deformity
image Monteggia: mid-ulnar fracture with angulation and radial dislocation
image Galeazzi: radial diaphysis fracture with disruption of distal radioulnar joint
image Open reduction and fixation preferred treatment in adults, with Monteggia and Galeazzi “fractures of necessity”

• Distal

image Radius: Colles fracture, proximal to styloid process, with dorsal deviation of distal fragment(s) and wrist

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