Forearm – Dorsal Approach (Thompson)

Modern Study Review (AI-Generated)

High-Yield Summary

The Thompson dorsal approach to the forearm is a reliable, extensile surgical corridor primarily used for open exposure of the radial shaft and distal radius, especially in fracture fixation and hardware removal. It utilizes a safe internervous plane between the radial nerve–innervated extensor carpi radialis brevis (ECRB) and the posterior interosseous nerve (PIN)–innervated extensor digitorum communis (EDC) or extensor pollicis longus (EPL). This approach remains the gold standard for direct radial shaft access, although minimally invasive and arthroscopic techniques have emerged as adjuncts in select cases.

Applied Anatomy & Intervals

Internervous Interval

• Proximal: Between ECRB (radial nerve) and EDC (PIN)
• Distal: Between ECRB (radial nerve) and EPL (PIN)

Anatomic Landmarks

• Lateral epicondyle of the humerus (just anterior)
• Lister’s tubercle on the distal radius (ulnar side)

Patient Positioning & Setup

• Table Type: Standard operating table with pneumatic tourniquet capability
• Patient Position: Supine, arm placed on a hand table or arm board
• Specialized Equipment:
• Pneumatic tourniquet on the upper arm
• Limb positioner or assistant for forearm supination/pronation
• C-arm fluoroscopy positioned for AP and lateral views of the radius

Surgical Technique (The “Vital Steps”)

Incision & Superficial Dissection

• Make a straight longitudinal incision from just anterior to the lateral epicondyle to the ulnar side of Lister’s tubercle
• Incise the fascia overlying the extensor compartments
• Identify and develop the interval between ECRB and EDC at midshaft level
• Distally, develop the interval between ECRB and EPL

Deep Dissection & Exposure

• Proximal third:
• Identify the supinator muscle
• Locate the PIN as it emerges ~1 cm distal to the supinator’s distal edge, between its deep and superficial heads
• Carefully dissect and protect the PIN
• Fully supinate the forearm to expose the anterior radius
• Detach the supinator insertion from the anterior radius for exposure

• Middle third:
• Identify abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendons crossing the dorsal radius
• Retract these tendons off the bone and incise along their superior and inferior borders for exposure

• Distal third:
• Separate ECRB and EPL to expose the lateral border of the distal radius

The “Danger Zone”

Post-Operative Pearl

Encourage early gentle wrist and finger mobilization to prevent stiffness. Limit forearm supination/pronation initially to protect the repaired supinator muscle and avoid irritation of the PIN.

Classic Clinical Notes

Forearm – dorsal approach (Thompson)

• Position: Supine with tourniquet

• Incision: Straight incision from just anterior to lateral epicondyle to ulnar side of Lister’s tubercle

• Internervous plane:
• Proximal: ECRB (radial nerve) & EDC (PIN)
• Distal: ECRB (radial nerve) & EPL (PIN)

• Superficial dissection:
• Incise fascia
• Interval between ECRB & EDC
• Start midshaft
• Interval between ECRB & EPL

• Deep dissection:
• Proximal 1/3:

> Identify supinator
> Locate PIN as it emerges 1 cm from distal end of muscle between deep & superficial heads
> Dissect nerve out of supinator
> Fully supinate forearm
> Detach supinator at insertion from anterior aspect of radius

• Middle 1/3:

> APL & EPB cross dorsal aspect of radius
> Retract off bone & make incision along their superior & inferior borders

• Distal 1/3:

> Separating ECRB & EPL exposes lateral border of radius

• Dangers:
• PIN – identify carefully because in 25% it touches the dorsal aspect of radius at level of biceps tuberosity

Last Updated on January 25, 2026 by orthonet