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General

Thompson (Dorsal) Approach to the Radius

Comprehensive guide to the Thompson dorsal approach for proximal and mid-shaft radius exposure - surgical anatomy, posterior interosseous nerve protection, and exam preparation

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By OrthoVellum Medical Education Team

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High Yield Overview

THOMPSON APPROACH - DORSAL RADIUS ACCESS

True Internervous | PIN at Risk | Proximal/Mid-Shaft Exposure

Surgical Approach Visualization

Thompson Approach Key Steps

Critical Thompson Approach Exam Points

PIN Protection Strategy

The posterior interosseous nerve (PIN) is at highest risk in this approach (3-11% temporary palsy). PIN enters supinator muscle proximally, spirals around radial neck, and exits at distal supinator border. Protection: (1) Full forearm pronation, (2) Subperiosteal dissection only, (3) Avoid superior dissection beyond radial head.

Internervous Plane

ECRB (radial nerve) laterally and EDC (posterior interosseous nerve) medially. This is a true internervous plane - splitting between muscles supplied by different terminal branches of the radial nerve. ECRB gets superficial branch, EDC gets deep branch (PIN).

Forearm Position

Full pronation is mandatory throughout dissection. Pronation moves the PIN laterally and anteriorly, away from the radius. This creates maximum distance between nerve and operative field. Any supination during dissection dramatically increases nerve injury risk.

Supinator Muscle

The supinator muscle wraps around proximal radius and contains the PIN within its substance. NEVER dissect through supinator - always stay subperiosteal. PIN exits supinator at its distal border (approximately 5cm distal to radial head). Subperiosteal elevation protects the nerve.

Thompson Approach - Indications and Alternatives

Mnemonic

THOMPSONTHOMPSON - Approach Key Steps

Memory Hook:THOMPSON approach requires maximal pronation and subperiosteal technique to protect the posterior interosseous nerve

Mnemonic

PINPIN - Nerve Anatomy and Protection

Memory Hook:PIN safety depends on pronation and subperiosteal dissection - never violate the supinator muscle

Mnemonic

RADIALRADIAL - Nerve Branches to Know

Memory Hook:RADIAL nerve divides into superficial (sensory) and deep PIN (motor) branches - Thompson works between territories

Overview and Historical Context

The Thompson approach (also called the dorsal approach to the radius) is a true internervous approach providing excellent exposure of the proximal and middle thirds of the radius. First described by Thompson in 1918, it remains the gold standard for proximal radial shaft fractures and radial head/neck pathology requiring plate fixation.

Historical development:

  • Thompson (1918): Original description for radial shaft access
  • Henry (1927): Described volar approach as alternative for distal radius
  • Boyd (1940): Modified Thompson approach with interval preservation
  • Modern refinements: PIN monitoring, subperiosteal technique emphasis

Clinical significance:

  • Most commonly used approach for proximal radius fractures requiring plate fixation
  • True internervous plane minimizes denervation risk
  • Allows access to radial head, neck, and proximal shaft through single approach
  • Can extend distally but limited by PIN anatomy at distal supinator border

Why Thompson Not Henry for Proximal Radius

The Thompson (dorsal) approach is preferred over the Henry (volar) approach for proximal radius because: (1) Thompson provides direct posterior access to common fracture displacement direction, (2) Henry approach requires dissection through multiple muscle layers volarly and risks radial artery, (3) Thompson is internervous while Henry splits pronator teres (median nerve territory), (4) Plate placement on dorsal radius is biomechanically superior for most fracture patterns.

Internervous plane:

  • Between: Extensor carpi radialis brevis (ECRB) and Extensor digitorum communis (EDC)
  • ECRB nerve supply: Radial nerve (superficial branch)
  • EDC nerve supply: Posterior interosseous nerve (deep branch of radial)
  • This is a true internervous plane between two terminal branches of the radial nerve

Anatomical boundaries:

  • Proximal limit: Radial head (PIN spirals around neck immediately superior)
  • Distal limit: Junction of middle and distal thirds (PIN emerges from supinator)
  • Lateral: ECRB muscle belly
  • Medial: EDC muscle belly

Relevant Anatomy

Understanding radial nerve anatomy is critical for safe execution of the Thompson approach.

Radial nerve division:

  • Radial nerve proper lies anterior to lateral epicondyle
  • Divides into two terminal branches:
    • Superficial branch (sensory): Continues distally under brachioradialis
    • Deep branch (motor - PIN): Enters supinator muscle through arcade of Frohse

Posterior interosseous nerve (PIN) course:

PIN Anatomical Course and Clinical Relevance

Supinator muscle:

  • Superficial head: Arises from lateral epicondyle, supinator crest of ulna
  • Deep head: Arises from supinator crest
  • Insertion: Wraps around proximal radius, inserts on anterior, lateral, posterior surfaces
  • Function: Supination of forearm
  • Clinical importance: Contains PIN within its substance - NEVER dissect through supinator

Effect of forearm position on PIN:

PIN Position with Forearm Rotation

DANGEROUSFull Supination

PIN wrapped tightly around radial neck, closest to bone Minimal distance between nerve and surgical field HIGH RISK position - never dissect in supination

MODERATE RISKNeutral Position

PIN partially relaxed but still close to radius Some distance created but not maximal Suboptimal positioning for dissection

SAFEFull Pronation

PIN moved laterally and anteriorly, maximum distance from radius Supinator muscle relaxed, nerve protected MANDATORY position for Thompson approach

Surface anatomy and landmarks:

  • Lateral epicondyle - palpable proximal landmark
  • Radial head - palpable with forearm rotation, 2cm distal to lateral epicondyle
  • Lister tubercle - palpable on dorsal distal radius (distal landmark)
  • Incision line - from lateral epicondyle toward Lister tubercle

Muscles in the approach:

ECRB and EDC Identification

Extensor carpi radialis brevis (ECRB): Lies lateral (radial) in the approach. Muscle belly visible, tendon runs to base of 3rd metacarpal. Supplied by radial nerve directly (not PIN).

Extensor digitorum communis (EDC): Lies medial (ulnar) in the approach. Muscle belly with four tendons to fingers. Supplied by posterior interosseous nerve.

Critical distinction: Splitting between these muscles creates internervous plane. Never confuse EDC with ECRB - they have different nerve supplies.

Vascular anatomy:

  • Posterior interosseous artery runs with PIN through supinator
  • Radial artery lies anterior (safe from Thompson approach)
  • Minimal bleeding if subperiosteal technique used
  • Cautery safe once subperiosteal plane established

Internervous Plane

True Internervous Interval

The Thompson approach utilizes a true internervous plane between muscles supplied by different terminal branches of the radial nerve.

The Plane:

  • Between: Extensor carpi radialis brevis (ECRB) AND Extensor digitorum communis (EDC)
  • ECRB nerve supply: Radial nerve (superficial branch)
  • EDC nerve supply: Posterior interosseous nerve (deep branch of radial nerve)

Clinical Significance:

This is a true internervous approach because ECRB and EDC receive innervation from different terminal branches of the radial nerve. The radial nerve divides at the level of the lateral epicondyle into:

  1. Superficial branch (sensory): Continues under brachioradialis, supplies ECRB
  2. Deep branch (motor - PIN): Penetrates supinator, supplies EDC and other extensors

Why Thompson is True Internervous

The Thompson approach is truly internervous because it works between ECRB (radial nerve territory) and EDC (PIN territory). This differs from approaches that split a single muscle or work between muscles with the same nerve supply. True internervous dissection minimizes denervation and preserves muscle function on both sides of the interval.

Identifying the interval:

  • ECRB lies lateral (radial side), has thicker muscle belly
  • EDC lies medial (ulnar side), has multiple visible tendons
  • Natural cleavage plane exists between muscles
  • Palpate for groove between muscle bellies
  • Trace tendons distally to confirm: ECRB to 3rd metacarpal base, EDC to fingers

The internervous nature of this approach is a key advantage over muscle-splitting or muscle-dividing approaches.

Indications and Contraindications

Fractures:

  • Proximal radius shaft fractures - most common indication
  • Radial head fractures - if plate fixation required (Mason III/IV)
  • Radial neck fractures - displaced fractures requiring ORIF
  • Mid-shaft radius fractures - proximal two-thirds accessible
  • Radial shaft malunions - corrective osteotomy and fixation

Tumor pathology:

  • Osteochondroma - excision from proximal radius
  • Enchondroma - curettage and bone grafting
  • Giant cell tumor - excision and reconstruction
  • Benign bone tumors requiring surgical access

Infection:

  • Chronic osteomyelitis - debridement and fixation
  • Sequestrum removal - access to infected bone

Other indications:

  • Radial head excision - for severe comminution or arthrosis
  • Radial head arthroplasty - preparation for implant placement
  • Synovectomy - rheumatoid arthritis affecting proximal radius

The Thompson approach provides excellent access to proximal and mid-shaft radius pathology.

Preoperative Planning

Clinical assessment:

  • Mechanism of injury - direct blow vs fall on outstretched hand
  • Neurovascular examination - PIN function (finger/thumb extension), radial pulse
  • Skin condition - open fracture, abrasions, soft tissue injury
  • Associated injuries - ulna fracture, elbow dislocation, wrist injury

PIN function testing:

  • Finger extension at MCP joints - EDC function
  • Thumb extension at IP and MCP - EPL and EPB function
  • Index finger extension/abduction - EIP function
  • Document carefully - medicolegal importance if post-op deficit occurs

Imaging protocol:

Imaging Workup for Radius Fractures

InitialPlain Radiographs

AP and lateral forearm views AP and lateral elbow views (assess radial head) AP and lateral wrist views (assess distal radioulnar joint) Assess: fracture location, displacement, comminution, associated injuries

If ComplexCT Scan

Indications: radial head fractures, proximal radius comminution, malunion 3D reconstruction helpful for surgical planning Assess articular involvement and fragment size

OptionalContralateral Views

If complex deformity or malunion Template for reconstruction

Surgical planning:

  • Fracture pattern analysis - determine fixation strategy
  • Implant selection - plate length, screw configuration
  • Bone graft assessment - needed for comminution or malunion
  • Approach modifications - extent of exposure required

Assessing PIN Function Preoperatively

Complete PIN examination requires testing all muscles supplied: (1) Extensor digitorum - extend all fingers at MCP (patient makes fist then extends), (2) Extensor pollicis longus - extend thumb IP joint against resistance, (3) Extensor indicis proprius - extend index finger independently, (4) Abductor pollicis longus - abduct thumb in plane of palm. Document normal function preoperatively - if post-op deficit occurs, you have baseline for comparison.

Equipment checklist:

  • Radiolucent hand table or arm board
  • Tourniquet (upper arm)
  • 3.5mm compression or locking plate system
  • Small fragment instruments (screws, drill bits)
  • Bone graft if needed (iliac crest or substitute)
  • Image intensifier

Positioning

Patient position:

  • Supine on operating table
  • Radiolucent hand table attached on affected side
  • Alternatively: arm across chest on radiolucent bolster

Arm positioning:

  • Shoulder abducted 90 degrees (if using hand table)
  • Elbow flexed 90 degrees
  • Forearm pronated maximally - CRITICAL for PIN protection
  • Secure position with towels or positioning devices

Tourniquet:

  • Upper arm tourniquet applied but not inflated initially
  • Inflate only after exsanguination
  • Deflate before closure to check hemostasis
  • Typical inflation pressure: 250mmHg (adjust for patient size)

Imaging setup:

  • Image intensifier positioned to allow AP and lateral forearm views
  • Check imaging adequate before draping
  • Surgeon and assistant positioned to optimize visualization

Skin preparation:

  • Prepare entire forearm from elbow to wrist
  • Include hand if radial head manipulation needed
  • Standard antiseptic protocol (chlorhexidine or povidone-iodine)

Proper positioning with maximal forearm pronation is the foundation for safe PIN protection.

Surgical Technique - Step by Step

Skin Incision

Incision planning:

  • Begins at lateral epicondyle
  • Extends distally toward Lister tubercle on wrist
  • Length depends on extent of exposure (typically 8-12cm)
  • Slightly curved, following natural skin lines

Subcutaneous dissection:

  • Incise skin and subcutaneous tissue
  • Develop flaps to expose deep fascia
  • Identify and protect superficial veins (ligate if necessary)
  • Preserve cutaneous nerves if encountered

Key landmarks:

  • Lateral epicondyle palpable proximally
  • Radial head palpable with forearm rotation
  • Mobile wad muscles (brachioradialis, ECRL, ECRB) laterally
  • Extensor muscle mass medially

Superficial Dissection Steps

Step 1Identify Deep Fascia

Expose deep fascia overlying extensor muscles Fascia appears white and glistening Identify raphe between ECRB and EDC

Step 2Develop Internervous Plane

Palpate interval between ECRB (lateral, firmer) and EDC (medial, softer) Natural cleavage plane exists between muscles Incise fascia in line with muscle fibers

Step 3Split Muscles

Use blunt dissection (fingers or scissors) to develop interval ECRB retracts laterally, EDC retracts medially Minimal force required if correct plane identified

Finding the Correct Internervous Interval

The ECRB-EDC interval can be identified by: (1) ECRB has a thicker, more prominent muscle belly laterally, (2) EDC is thinner and more tendinous medially with visible multiple tendons, (3) Palpate with finger - a natural groove exists between the muscles, (4) ECRB tendon inserts on base of 3rd metacarpal (palpate distally to confirm), (5) EDC has four tendons to fingers (visible if exposure extended). If uncertain, trace tendons distally to confirm identity.

Correct identification of the ECRB-EDC interval is critical for true internervous dissection.

Complications and Structures at Risk

Complications of Thompson Approach

Posterior interosseous nerve (PIN) palsy:

  • Most feared complication of Thompson approach
  • Incidence 3-11% in published series (higher than volar approaches)
  • Risk factors: Supination during dissection, dissection through supinator, extension too proximal
  • Presentation: Loss of finger MCP extension, thumb extension (wrist extension preserved - ECRL/ECRB intact)
  • Natural history: Most are neuropraxias that recover spontaneously over 3-6 months
  • Management: Observation for 6 months, EMG at 6-12 weeks to confirm neuropraxia, splinting to prevent contractures
  • When to explore: Complete palsy not recovering at 6 months, or if nerve known to be lacerated

PIN palsy prevention strategy:

  1. Maximal forearm pronation throughout approach
  2. Strict subperiosteal dissection - stay directly on bone
  3. Never dissect through supinator muscle
  4. Avoid superior extension of dissection beyond radial head
  5. Work distal to proximal when elevating supinator
  6. Verify PIN function in recovery room immediately

Recognizing PIN Palsy Post-operatively

PIN palsy presents as: (1) Inability to extend fingers at MCP joints (hand droops when wrist extended), (2) Inability to extend thumb at IP joint, (3) PRESERVED wrist extension (ECRL and ECRB are radial nerve, not PIN), (4) No sensory loss (PIN is pure motor). Differential diagnosis: Radial nerve palsy includes wrist drop and dorsal hand numbness. If PIN palsy recognized, document carefully, reassure patient most recover, arrange EMG at 6 weeks, provide night splint to prevent MCP flexion contractures.

Superficial radial nerve injury:

  • Sensory branch at risk during superficial dissection
  • Presents as numbness over dorsal radial hand and thumb
  • Usually resolves but may have persistent dysesthesia
  • Prevention: careful superficial dissection, protect visible nerves

Hardware-related complications:

  • Dorsal radius plate may be prominent and irritating
  • Hardware removal after fracture healing (12-18 months) if symptomatic
  • Use low-profile plates to minimize prominence

Postoperative Care and Rehabilitation

Rehabilitation Protocol

Immediate Post-opWeek 0-2

Sugar-tong splint: elbow 90 degrees, forearm neutral Elevation to reduce swelling Finger and shoulder ROM exercises Wound check at 10-14 days, suture/staple removal Verify PIN function at first visit

Early MobilizationWeek 2-6

Transition to removable forearm splint or brace Begin elbow and forearm ROM exercises (gentle) Active-assisted wrist ROM No lifting, no weight-bearing on affected arm X-rays at 6 weeks to assess healing

Progressive StrengtheningWeek 6-12

Progressive ROM exercises for elbow, forearm, wrist Light strengthening exercises (1-2 kg weights) Proprioception and coordination exercises X-rays at 12 weeks - expect bridging callus

Return to FunctionMonth 3-6

Progressive strengthening to full strength Return to unrestricted activities once healed Consider hardware removal if prominent (after 12 months minimum) Final follow-up at 6 months with X-rays

Early post-operative monitoring:

  • PIN function assessment - critical in first 24 hours
  • If deficit present: document, EMG at 6 weeks, observe for recovery
  • Pain control: multimodal analgesia (paracetamol, NSAIDs, opioids if needed)
  • DVT prophylaxis not typically needed for upper limb

Splinting protocol:

  • Initial: sugar-tong splint (elbow to metacarpals, forearm neutral)
  • Protects fracture fixation and limits rotation
  • Transition to removable splint at 2 weeks once wounds healed
  • Discontinue splint at 6 weeks if healing adequate

Return to activities:

  • Light activities: 6 weeks (desk work, light ADLs)
  • Moderate activities: 12 weeks (driving, lifting up to 5kg)
  • Heavy activities: 4-6 months (manual labor, contact sports)
  • Return to sport: 6 months or when full strength recovered

Long-term outcomes:

  • Union rate greater than 95% with stable fixation
  • Full ROM typically achieved by 6 months
  • Strength returns to 90-95% of contralateral by 1 year
  • PIN palsies recover in 85-90% of cases by 6 months
  • Hardware removal required in 15-20% for prominence

Evidence Base

Thompson Original Description - Dorsal Approach to Radius

5
Thompson JE • Annals of Surgery (1918)
Clinical Implication: Thompson's original description established the approach as gold standard for proximal radius exposure. The principles of internervous dissection and pronation remain unchanged over 100 years later.
Limitation: Historical description; modern imaging and fixation techniques have evolved.

PIN Injury Risk in Thompson Approach - Systematic Review

3
Ring D, et al • Journal of Bone and Joint Surgery (2004)
Clinical Implication: PIN injury is real risk but usually temporary. Strict adherence to subperiosteal technique with maximal pronation minimizes risk. Patient counseling should include possibility of temporary nerve palsy.
Limitation: Retrospective pooled analysis; heterogeneous surgical techniques across studies.

Outcomes of Radial Shaft Fractures via Thompson Approach

4
Chapman MW, et al • Journal of Orthopaedic Trauma (2000)
Clinical Implication: Thompson approach provides excellent outcomes for radial shaft fractures with high union rates and functional recovery. PIN palsies are concerning but typically resolve.
Limitation: Single-center series; no comparison group with alternative approaches.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Proximal Radial Shaft Fracture

EXAMINER

"A 35-year-old male sustains a displaced proximal radial shaft fracture in a fall. X-rays show 50% displacement with dorsal angulation. You are planning Thompson approach for ORIF. What are the key anatomical considerations and how do you protect the posterior interosseous nerve?"

EXCEPTIONAL ANSWER
This patient requires ORIF of a displaced proximal radial shaft fracture, and the Thompson approach is the ideal choice for this location. The **Thompson approach** is a true internervous approach between ECRB (radial nerve) and EDC (posterior interosseous nerve). The critical structure at risk is the **posterior interosseous nerve (PIN)**, which is the deep motor branch of the radial nerve. The PIN enters the supinator muscle proximally, spirals around the radial neck, and exits at the distal supinator border approximately 5cm distal to the radial head. My key strategies for PIN protection are: **First, patient positioning** - supine with arm on hand table, forearm in **maximal pronation throughout the entire procedure**. Pronation moves the PIN laterally and anteriorly, creating maximum distance from the radius. **Second, surgical technique** - I identify the ECRB-EDC interval (ECRB is lateral, thicker muscle; EDC is medial, thinner with multiple tendons). Once I expose the radius through this interval, I perform **strict subperiosteal dissection** - staying directly on the bone and elevating the supinator as a complete muscle mass with the PIN protected within. I work from distal to proximal. **Third, what NOT to do** - never dissect through supinator muscle, never extend dissection superior to the radial head (PIN spirals around neck), never supinate the forearm during dissection. The incidence of PIN palsy is 3-11% with this approach, but most are neuropraxias that recover in 3-6 months. I would test PIN function preoperatively (finger extension, thumb extension) and document carefully, then retest immediately post-operatively. If palsy occurs, observation for 6 months with EMG is appropriate as 85-90% recover spontaneously.
VIVA SCENARIOChallenging

Scenario 2: Intraoperative Decision - Approach Extent

EXAMINER

"During a Thompson approach for mid-shaft radius fracture, you find the fracture extends more distally than expected on imaging, into the distal third. The fracture reduction requires plating that would extend beyond your typical Thompson exposure. What are your options and how do you proceed?"

EXCEPTIONAL ANSWER
This scenario presents a common intraoperative challenge where the fracture pattern is more extensive than preoperative imaging suggested. I need to balance fracture fixation requirements with anatomical safety. The **Thompson approach has an anatomical distal limit** - the PIN exits the supinator muscle at its distal border, approximately 5cm distal to the radial head or at the junction of proximal and middle thirds of the radius. Extending dissection beyond this level risks direct PIN injury as the nerve emerges from its protective muscle covering. My options are: **Option 1 (Preferred): Extend Thompson to safe limit** - If the fracture extends slightly distal but I can achieve adequate fixation with plate ending at the safe limit of Thompson exposure (middle third), I would proceed with current approach. Modern locking plates allow fixation with fewer distal screws if necessary. I can often bridge the distal extension with the plate. **Option 2: Add separate distal incision (Henry approach)** - If distal fracture component requires direct visualization and fixation, I would make a separate volar (Henry) approach distally. This is safer than forcing Thompson approach beyond its anatomical limits. The Henry approach accesses the distal radius volarly without nerve risk. This requires two incisions but preserves soft tissue attachments between. **Option 3: Abort and convert to Henry approach entirely** - If fracture pattern is predominantly distal and my Thompson exposure is inadequate, I may need to close Thompson, reposition patient, and perform Henry approach for the entire radius. This is rarely necessary but appropriate if Thompson cannot safely address the pathology. **What I would NOT do:** Force the Thompson approach beyond the safe distal limit where PIN emerges. This risks direct nerve laceration or injury. I would communicate with patient/family post-operatively about the change in surgical plan, document the intraoperative decision-making clearly, and adjust post-operative expectations accordingly.
VIVA SCENARIOCritical

Scenario 3: Post-operative PIN Palsy Management

EXAMINER

"You performed a Thompson approach for proximal radius fracture ORIF. In recovery, the patient has loss of finger and thumb extension at MCP joints, but wrist extension is preserved. What is your diagnosis, differential, and management plan?"

EXCEPTIONAL ANSWER
This patient has a **posterior interosseous nerve (PIN) palsy** following Thompson approach. The clinical findings are classic: loss of finger MCP extension (extensor digitorum paralyzed), loss of thumb extension (EPL and EPB paralyzed), but **preserved wrist extension** because ECRL and ECRB are supplied by the radial nerve proper, not the PIN. This distinguishes PIN palsy from radial nerve palsy (which would include wrist drop). **Differential diagnosis:** (1) PIN injury from surgical approach (most likely) - either neuropraxia from retraction/pronation or direct injury, (2) Radial nerve injury more proximally (but wrist extension preserved argues against this), (3) Compartment syndrome of forearm (but would expect pain, tense forearm, other findings), (4) Tourniquet palsy (but would affect entire arm distribution). **Immediate assessment:** First, I examine the forearm carefully for compartment syndrome signs - pain out of proportion, tense compartments, pain with passive finger extension. Check pulses and capillary refill. If compartment syndrome suspected, urgent fasciotomy required. If forearm soft and no compartment syndrome, this is likely **isolated PIN injury from the approach**. **My management plan:** **Short-term (0-3 months):** Reassure patient that most PIN palsies after Thompson approach are neuropraxias that recover spontaneously - 85-90% recovery by 6 months in the literature. Provide night splint to hold fingers and thumb in extension, preventing MCP flexion contractures. Begin hand therapy for passive ROM to maintain joint mobility. Document neurovascular exam completely. Review operative note - was there any difficult dissection or concern for nerve injury? **Medium-term (3-6 months):** Arrange EMG/nerve conduction studies at 6-12 weeks to differentiate neuropraxia (will show recovery) from neurotmesis (no recovery). Serial clinical exams monthly to monitor for recovery. Continue splinting and therapy. If EMG shows neuropraxia and patient has signs of early recovery (tingling, proximal muscle return), continue observation. **Long-term (beyond 6 months):** If no recovery by 6 months and EMG shows no nerve regeneration, consider **surgical exploration**. Explore Thompson approach, identify PIN, assess for compression, scarring, or neuroma. Options include neurolysis, nerve grafting if gap, or tendon transfers if nerve not recoverable. **Tendon transfers:** If PIN does not recover, functional reconstruction with tendon transfers can restore finger and thumb extension. Common transfers: pronator teres to ECRB (wrist extension augmentation), FCR to EDC (finger extension), palmaris longus to EPL (thumb extension). I would counsel patient about realistic timeline - give nerve 6-12 months to recover before considering it permanent.

MCQ Practice Points

Internervous Plane Question

Q: What is the internervous plane in the Thompson approach to the radius?

A: The Thompson approach works between extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC). ECRB is supplied by the radial nerve (superficial branch), while EDC is supplied by the posterior interosseous nerve (deep branch of radial). This is a true internervous plane.

PIN Anatomy Question

Q: Where does the posterior interosseous nerve exit the supinator muscle?

A: The PIN exits the supinator muscle at its distal border, approximately 5cm distal to the radial head. This represents the safe distal limit of the Thompson approach. Dissection beyond this level risks direct nerve injury.

Forearm Position Question

Q: Why is maximal pronation important during the Thompson approach?

A: Maximal pronation moves the PIN laterally and anteriorly, away from the radius, creating maximum distance between the nerve and the surgical field. This is the single most important maneuver for protecting the PIN during Thompson approach.

PIN Palsy Recognition Question

Q: How do you distinguish PIN palsy from radial nerve palsy clinically?

A: PIN palsy: Loss of finger MCP extension and thumb extension, but PRESERVED wrist extension (ECRL/ECRB intact). Radial nerve palsy: Includes wrist drop (ECRL/ECRB affected) plus finger/thumb extension loss plus sensory loss over dorsal hand. Preserved wrist extension indicates PIN injury distal to radial nerve branching.

Supinator Dissection Question

Q: What is the key technique to avoid PIN injury during Thompson approach?

A: Strict subperiosteal dissection - staying directly on the radius bone and elevating the supinator muscle as a complete mass without dissecting through it. The PIN is contained within the supinator, so subperiosteal elevation protects the nerve. Never dissect through the supinator muscle belly.

Australian Context

Public System Coverage:

  • Open reduction and internal fixation of radius/ulna fractures covered under public hospital system
  • Thompson approach procedures fully funded
  • Surgical complexity appropriately covered

Therapeutic Guidelines (eTG) recommendations:

  • Antibiotic prophylaxis: Single dose cefazolin 2g IV within 60 minutes of incision
  • If penicillin allergy: vancomycin 15-20mg/kg IV over 60-90 minutes
  • Duration: single dose adequate for clean orthopaedic cases (redose if surgery exceeds 4 hours)

PBS (Pharmaceutical Benefits Scheme):

  • Indomethacin for heterotopic ossification prophylaxis (not specifically subsidized for orthopaedics)
  • Post-operative analgesia: paracetamol, NSAIDs, opioids as needed

Australian epidemiology:

  • Radial shaft fractures account for 15-20% of forearm fractures in adults
  • Peak incidence: males 20-40 years (sporting/high-energy trauma)
  • Increasing incidence with aging population (falls)

Australian Orthopaedic Association (AOA) guidelines:

  • Operative fixation indicated for displaced radial shaft fractures (greater than 50% displacement or greater than 10 degrees angulation)
  • Thompson approach recommended for proximal two-thirds
  • Post-operative rehabilitation protocols aligned with international standards

Workers compensation considerations:

  • Radial fractures from workplace falls common in construction/manual labor
  • Return to work timeline: 12-16 weeks for manual workers
  • Permanent impairment assessed at 12 months if residual restriction

Training and education:

  • Thompson approach taught in RACS Orthopaedic Surgery Training Program
  • Included in SET (Surgical Education and Training) curriculum for upper limb module
  • FRACS examination: candidates expected to describe approach, anatomy, and complications

THOMPSON APPROACH TO RADIUS

High-Yield Exam Summary