Bado Classification (Paediatric) — Monteggia & Equivalents

Overview — The Monteggia Fracture-Dislocation

The Monteggia fracture-dislocation, originally described by Giovanni Battista Monteggia in 1814, is a fracture of the ulnar shaft with associated dislocation of the radial head at the proximal radioulnar joint and/or radiohumeral joint. It is a treacherous injury because the radial head dislocation is the critically important component — and it is frequently missed, particularly in children, where the mechanism and radiological appearances differ from adults. In children, Monteggia injuries account for approximately 1–2% of all paediatric forearm fractures and have a distinct spectrum of patterns, including the so-called `Monteggia equivalents` — injuries with the same biomechanical consequence (radial head dislocation with associated forearm injury) but with different fracture morphologies. Missed radial head dislocation leads to chronic pain, restricted forearm rotation, and neurological deficit.

The critical diagnostic rule: on ANY radiograph of a forearm injury, a line drawn through the long axis of the radial shaft (the `radiocapitellar line`) must pass through the centre of the capitellum on BOTH the AP and lateral views; if this line does NOT pass through the capitellum, the radial head is dislocated — regardless of what the ulna is doing; this rule applies to all ages and must be checked on every forearm X-ray; failure to apply this rule is the most common reason for a missed Monteggia injury
Epidemiology in children: peak incidence 4–10 years of age; boys affected more commonly than girls; typically a fall onto an outstretched hand; the mechanism and resulting fracture pattern determine the Bado type; the plastic (greenstick) nature of the paediatric ulna means that the ulna may angulate without a complete fracture — creating the `nightstick equivalent` or plastic bowing form of Monteggia injury

Bado Classification

Bado Type	Ulnar Fracture / Deformity	Radial Head Dislocation	Mechanism	Frequency
Type I — Anterior	Ulna fracture with anterior (volar) angulation; the ulna apex points anteriorly (the ulna bows or fractures into anterior angulation)	ANTERIOR dislocation of the radial head (the radial head dislocates anteriorly); visible on the lateral view as anterior displacement of the radial head relative to the capitellum; the radiocapitellar line fails to pass through the capitellum on the lateral view	Hyperpronation mechanism (forced pronation of the forearm — the proximal radius acts as a lever, displacing the radial head anteriorly while the ulna fractures or angulates anteriorly)	MOST COMMON — approximately 70% of all Monteggia injuries in children; the classic paediatric pattern
Type II — Posterior	Ulna fracture with posterior (dorsal) angulation; apex points posteriorly	POSTERIOR (or posterolateral) dislocation of the radial head; radiocapitellar line fails to intersect the capitellum on the lateral view (radial head is posterior)	Direct force on the dorsal forearm (dorsal axial loading); hyperflexion mechanism	~5–10% in children; more common in adults; posterior dislocation is less common in children because the paediatric radial head is more cartilaginous and more easily reduced anteriorly
Type III — Lateral	Ulna fracture with lateral (radial) angulation — the metaphyseal portion of the ulna (proximal ulnar metaphysis) fractures, creating a lateral-pointing deformity	LATERAL (radial-side) dislocation of the radial head; the radial head displaces laterally; best seen on the AP view	Varus stress on the extended elbow; forced adduction mechanism; the leverage of the applied force creates lateral ulnar angulation and lateral radial head displacement	~20–25% in children — the second most common paediatric type; the proximal ulnar metaphysis is the typical fracture site in this type in children (contrast with Type I which is usually diaphyseal)
Type IV — Combined	Fracture of BOTH the ulnar shaft AND the radial shaft (proximal third) — a `both-bones` forearm fracture combined with anterior dislocation of the radial head; both bones of the forearm are fractured	ANTERIOR dislocation of the radial head (same direction as Type I) combined with a radius shaft fracture proximal to the fracture of the ulna	High-energy combined mechanism	Rare — approximately 1–5%; children less commonly than adults; very high-energy injury; requires careful assessment of both radius and ulna fractures plus the radial head dislocation

Monteggia Equivalents in Children

Monteggia equivalents are injuries that share the biomechanical consequence of the classic Monteggia (i.e., radial head dislocation with associated forearm injury) but differ in the specific fracture morphology. They are particularly important in children because the paediatric periosteum and growth plate create unique fracture patterns not seen in adults.

Equivalent Type	Description	Key Point
Plastic bowing of the ulna + radial head dislocation	The ulna bows plastically (the periosteum remains intact; there is no discrete fracture line — the bone deforms permanently without fracturing); the radial head dislocates anteriorly; on plain X-ray, there is NO obvious fracture — only an increased anterior bow of the ulna; this is the most commonly MISSED Monteggia equivalent because there is no discrete fracture to prompt concern	ALWAYS draw the radiocapitellar line; plastic bowing with anterior radial head dislocation = Monteggia equivalent; treatment requires correction of the ulnar bow (either closed — under GA with three-point bending reduction) to reduce the radial head; the annular ligament interposition may prevent closed reduction → open reduction
Greenstick ulna fracture + radial head dislocation	A greenstick (incomplete) ulnar fracture with intact periosteum on the compression side; radial head dislocation is present; the incomplete nature of the fracture may disguise the severity of the injury	The greenstick ulna must be completed at the time of reduction to restore ulnar length and straightness — an incomplete greenstick fracture that springs back into angulation after reduction will prevent maintenance of radial head reduction; complete the fracture under anaesthesia and reduce and cast appropriately
Olecranon Salter-Harris fracture + radial head dislocation	An epiphyseal fracture of the olecranon (Salter-Harris Type I, II, or IV) with associated anterior radial head dislocation; the entire proximal ulna (olecranon + ulnar metaphysis) may angulate anteriorly with a physeal fracture at the olecranon	The olecranon physis contributes to the proximal ulnar length; ORIF of displaced olecranon physeal fractures is required; the radial head dislocation reduces once the ulnar length is restored by fixation
Coronoid fracture + radial head dislocation	A fracture of the coronoid process of the ulna with associated radial head dislocation; the coronoid fracture is typically Regan-Morrey Type I or II; this is more common in adults but can occur in adolescents	If the coronoid fracture involves >50% of the coronoid height (Regan-Morrey Type III) — elbow instability is the primary concern; combined coronoid + lateral collateral ligament repair may be needed; in children, smaller coronoid fractures are more likely to be avulsion from the capsular insertion

Management

Paediatric acute Monteggia (Type I — most common): closed reduction under general anaesthesia; (1) the ulnar fracture is reduced first (restoring ulnar length and alignment is the key step — this indirectly reduces the radial head); (2) the radial head typically reduces spontaneously as the ulnar length is restored; (3) above-elbow plaster cast is applied with the elbow in 90–110° of flexion and the forearm in supination (supination tightens the annular ligament and holds the radial head reduced); check the radiocapitellar line in both AP and lateral views on post-reduction X-ray under image intensifier before applying the cast; if the radial head does not reduce after adequate ulnar reduction → open reduction required (annular ligament interposition is the most common reason for irreducibility)
Open reduction indications: failed closed reduction (annular ligament interposition; irreducible radial head); chronic/missed Monteggia (more than 3–4 weeks old — soft tissue contractures prevent closed reduction); Type IV injuries; complex fracture patterns; associated neurovascular injury
Chronic (missed) Monteggia in children: an important and preventable complication of missed acute Monteggia injury; children with unrecognised radial head dislocation may present months to years later with painless or mildly painful restriction of elbow flexion, extension, and forearm rotation; a progressive cubitus valgus may develop; elbow OA develops in adulthood; management: open reduction of the radial head with ulnar corrective osteotomy (to restore ulnar bow and length) before the age of ~12 years; annular ligament reconstruction (Bell-Tawse procedure — using a strip of triceps fascia to reconstruct the annular ligament); reconstruction becomes progressively more difficult and less successful with increasing delay; radiological evidence of remodelling of the radial head (flattening) = poor prognosis for reduction
Neurological complications: the posterior interosseous nerve (PIN — deep branch of radial nerve) is the most commonly injured nerve; PIN injury occurs in approximately 10–20% of Monteggia fractures, particularly Type I (anterior dislocation compresses the PIN as it passes through the radial tunnel around the radial neck); typically a neuropraxia that recovers within 3–6 months; document neurological examination before and after reduction; persistent PIN palsy at 3–4 months → electrophysiological assessment and surgical exploration

Exam Pearls

Radiocapitellar line: line through the radial shaft axis must pass through the capitellum on BOTH AP and lateral views; if not → radial head is dislocated → Monteggia until proven otherwise; apply this rule to EVERY forearm X-ray in a child
Bado classification: Type I = anterior ulna angulation + anterior radial head dislocation (70% in children — most common); Type II = posterior; Type III = lateral (proximal ulnar metaphysis fracture, 20%); Type IV = both bones fracture + anterior dislocation
Most common paediatric type = Bado Type I (anterior); most common equivalent = plastic bowing of ulna (no fracture line — most commonly missed); always draw radiocapitellar line on elbow/forearm X-rays
Management Type I children: GA → reduce ulna (length restoration) → radial head reduces → above-elbow cast in supination + 90–110° flexion; confirm radiocapitellar line after reduction; if radial head not reduced after adequate ulnar reduction → open (annular ligament interposition)
Chronic missed Monteggia: presents months-years later with restricted ROM ± painless; ulnar corrective osteotomy + open radial head reduction + annular ligament reconstruction (Bell-Tawse); before age 12 years for best results; flattened radial head = poor prognosis
Nerve complication: PIN (posterior interosseous nerve — deep branch of radial nerve); neuropraxia in 10–20% Type I; wrist drop + inability to extend fingers/thumb (no sensory loss — PIN is pure motor); recovers in 3–6 months; persistent at 3–4 months → EMG + exploration
Monteggia equivalents: plastic bowing (no fracture — most missed); greenstick ulna (complete the fracture at time of reduction); olecranon SH fracture + anterior radial head dislocation; coronoid fracture + radial head dislocation

Bado Classification (Paediatric) — Monteggia & Equivalents

References

Share Wiki