why thomson approch in preffred in monteggia fractute
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Thompson approach Monteggia fracture surgical exposure
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Monteggia fracture radial head dislocation surgical approach posterior interosseous nerve
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Why the Thompson Approach is Preferred in Monteggia Fracture
Background: Monteggia Fracture
A Monteggia fracture is a fracture of the proximal ulna combined with dislocation of the radial head. Surgical fixation requires:
- Reducing and plating the ulna fracture
- Addressing the radial head (and often the annular ligament/proximal radioulnar joint)
The Thompson Approach (Posterior Interosseous / Dorsal Approach to the Forearm)
The Thompson approach is a dorsal (posterior) approach to the proximal forearm, passing between extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC), giving access to the proximal radius and radiocapitellar joint.
Why It Is Preferred — Key Reasons
1. Excellent Exposure of the Radial Head and Proximal Radius
- The Thompson approach provides direct visualization of the radiocapitellar joint, allowing:
- Confirmation and reduction of the dislocated radial head
- Repair or reconstruction of the annular ligament
- Access for radial head fixation or replacement if needed
2. Safe Interval / Nerve-Sparing
- The internervous plane lies between:
- ECRB (supplied by the radial nerve, proximal to the split)
- EDC (supplied by the posterior interosseous nerve — PIN)
- Critically, the posterior interosseous nerve (PIN) is identified and protected throughout
- The PIN wraps around the radial neck and is at high risk in Monteggia injuries (both from the original injury and from surgery)
- The Thompson approach allows the surgeon to directly visualize and retract the PIN, dramatically reducing iatrogenic nerve injury
3. Simultaneous Ulna Access
- Combined with a posterior/medial ulna incision (ulna is subcutaneous), the Thompson approach can be used through the same or an adjacent incision, allowing:
- Ulna ORIF (open reduction internal fixation)
- Radial head reduction — in a single operative field
- This avoids the need for two entirely separate approaches
4. Avoidance of the Anterior Approach Hazards
- The anterior (Henry) approach to the proximal forearm passes near the radial artery and requires pronation/supination maneuvers close to neurovascular structures
- The posterior Thompson approach avoids the anterior neurovascular bundle
- In Monteggia fractures, where there is already significant soft tissue disruption, the Thompson approach is safer
5. Access to Annular Ligament
- The annular ligament — which is often torn in Monteggia injuries — is best visualized and repaired posterolaterally, exactly where the Thompson approach operates
Comparison: Thompson vs. Henry (Anterior) Approach
| Feature | Thompson (Dorsal) | Henry (Anterior/Volar) |
|---|---|---|
| Interval | ECRB / EDC | Brachioradialis / FCR (proximally) |
| Nerve at risk | PIN (identified & protected) | Radial nerve (anterior branch) |
| Radial head exposure | Excellent (direct) | Moderate |
| Annular ligament access | Direct | Limited |
| Ulna access | Combined with posteromedial | Separate incision often needed |
| Use in Monteggia | Preferred | Less commonly used |
Summary
The Thompson approach is preferred in Monteggia fractures because it:
- Provides direct access to the radial head and annular ligament
- Allows identification and protection of the PIN (the nerve most at risk)
- Can be combined with posterior ulna fixation in a single operative field
- Avoids the anterior neurovascular structures (radial artery, main radial nerve trunk)
The ability to directly protect the posterior interosseous nerve while simultaneously reducing the radial head dislocation and repairing the annular ligament makes it the workhorse approach for this injury.
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