Variants of monteggia fracture
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Variants (Classification) of Monteggia Fracture
Definition
A Monteggia fracture-dislocation (or "Monteggia lesion") is a fracture of the proximal ulna combined with dislocation of the radial head. The term was first used by Giovanni Battista Monteggia in 1814, who described fracture of the proximal ulna with anterior dislocation of the radial head. Bado (1967) expanded the definition to include all four directional variants.
Bado Classification (Primary System)
Classification is based on the direction of radial head dislocation and the angulation of the ulnar fracture.
| Bado Type | Radial Head Dislocation | Ulnar Fracture | Additional Notes |
|---|---|---|---|
| I | Anterior | Diaphysis - apex anterior angulation | Most common in children (~60-70%); hyperpronation or direct blow mechanism |
| II | Posterior or posterolateral | Diaphysis - apex posterior angulation | Most common in adults (~80%); often associated with radial head or coronoid fractures |
| III | Lateral or anterolateral | Proximal ulnar metaphysis | Almost exclusively in children; associated with cubitus varus |
| IV | Anterior | Proximal 1/3 ulna + fracture of proximal 1/3 radius at the same level | Rarest type; occurs exclusively in adults |
Jupiter Modification of Bado Type II
Because Type II injuries in adults are the most common and most complex (frequently associated with radial head and coronoid fractures, threatening elbow stability), Jupiter et al. subclassified them by the location of the ulnar fracture:
| Subtype | Location of Ulnar Fracture |
|---|---|
| IIA | Very proximal - distal olecranon and coronoid process |
| IIB | Junction of proximal metaphysis and diaphysis (metadiaphyseal - not involving coronoid) |
| IIC | Diaphyseal |
| IID | Complex - spans from olecranon into diaphysis (proximal 1/3 involving coronoid and olecranon with dislocation) |
Jupiter subclassification is important because IIA and IID injuries have significant articular involvement and are among the most technically demanding fractures of the elbow.
Monteggia Equivalents (Variants)
These are injuries that share the same biomechanical pattern but differ in one component:
- Radial head fracture instead of dislocation (fracture-equivalent): The annular ligament fails through bone rather than by pure dislocation. This is an important pitfall - a missed radial head fracture in the context of a proximal ulna fracture should raise suspicion for a Monteggia equivalent.
- Plastic deformation of the ulna (especially in children): No discrete fracture line visible; the ulna undergoes bowing without a visible break, yet the radial head dislocates. This is why ALL forearm fracture X-rays in children must include elbow views.
- Transolecranon fracture-dislocations: Can be considered variants of Bado Type II - involve fracture-dislocation of the olecranon with associated coronoid fractures, radial head fractures, and lateral collateral ligament injuries (sometimes called "terrible triad" variants).
Frequency Summary
- Children: Type I is most frequent (~60%)
- Adults: Type II accounts for up to 80% of adult Monteggia injuries
Key Clinical Points
- Radial head reduction: In most cases, anatomic reduction of the ulna leads to automatic reduction of the radial head. If the radial head does not reduce after anatomic ulnar fixation, the most common cause is a non-anatomic ulnar reduction; if the ulna is correctly reduced and the radial head still will not reduce, open reduction via a separate approach is required to address interposed annular ligament.
- PIN (posterior interosseous nerve) injury: Occurs in ~10% of cases, usually a neurapraxia that resolves spontaneously; observe for 3 months before considering further workup.
- All Monteggia fractures in adults should be treated with ORIF. Nonoperative management is reserved only for patients with significant comorbidities who cannot tolerate surgery.
- Chronic/missed Monteggia fracture: May require ulnar osteotomy and annular ligament reconstruction.
Sources: Rockwood and Green's Fractures in Adults 10th ed. 2025; Campbell's Operative Orthopaedics 15th ed. 2026; Miller's Review of Orthopaedics 9th ed.
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