Paediatric Monteggia Fracture Dislocation - ORIF Ulna & Radial Head Reduction

Indication. A paediatric Monteggia fracture-dislocation — a fracture of the ulna with dislocation of the radial head — needing surgery. Operate when the injury is displaced and unstable, has been missed, or has failed closed treatment. The goal is always the same: an anatomic, stable reduction of the ulna, which in the acute setting reduces the radial head in about 90% of cases. Assess the whole injury before deciding. Classify the Bado type, document baseline nerve function (especially the PIN), and look beyond the obvious ulnar fracture:

Relative indications — Bado Type I in an adolescent with a reliable closed reduction but an unstable radial head (consider percutaneous fixation of the ulna first); a minimally displaced ulnar fracture with radial head subluxation (trial closed reduction first); a Type III lateral dislocation in a young child (some treat closed if stable). Pre-operative planning. - Imaging: AP and lateral forearm and elbow views; draw the radiocapitellar line on ALL views (AP, lateral, oblique); assess for plastic deformation of the radius (radial bowing on the AP view); compare with the contralateral side for subtle deformity; a CT if the case is chronic with a bone block or a coronoid fracture.

• Classification: the Bado type (I-IV) sets the approach and prognosis; separate acute (less than 3 weeks) from chronic (more than 3 weeks), which drives the need for annular ligament reconstruction; identify associated injuries (coronoid, olecranon, proximal radius fractures).
• Implants and strategy: 2.4 mm or 2.7 mm plate versus intramedullary wire (by age and pattern); plan correction of any radius plastic deformation (osteoclasis versus formal osteotomy); anticipate annular ligament reconstruction if chronic or the ligament is known to be disrupted; reserve a transarticular K-wire for when reconstruction is not feasible (remove by 3 weeks maximum). Special considerations in children. Minimal periosteal stripping (children have an excellent periosteal sleeve for healing); avoid transphyseal screws near the proximal ulnar physis; smaller implants are often adequate (2.4 mm versus 2.7 mm in adolescents); a lower threshold for intramedullary fixation in young children (less soft-tissue trauma). Consent specifically for PIN injury (loss of thumb/finger extension, usually recovering), stiffness and loss of rotation, redislocation needing revision, radioulnar synostosis, and (in late/unrecognised cases) a poorer outcome. Setup. Supine with the arm on a radiolucent arm table, upper-arm tourniquet, shoulder abducted 70-90 degrees and elbow flexed. Image intensifier set up for AP and lateral views of both the elbow and the forearm.

The goal: reduce and fix the ulna anatomically through the direct subcutaneous approach, correct any plastic deformation of the radius, and reduce the radial head — reconstructing the annular ligament only when the head is unstable or the case is chronic. The exposure of the ulna is laid out in full as the early steps below (and in depth on the Boyd approach to the proximal forearm page).

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Rehabilitation | Phase | Timing | Immobilisation | Milestones & therapy | |-------|--------|-----------------|----------------------| | 1 | 0-6 weeks | Long arm cast, 90 degrees flexion, forearm supinated | X-ray at 1 week (check reduction maintained); 3 weeks (remove transarticular K-wire if used); 6 weeks (union assessment, begin ROM) | | 2 | 6-12 weeks | Removable splint for protection | Gentle active ROM; avoid aggressive passive stretching | | 3 | 3-6 months | None | Progressive return; expect full or near-full ROM by 3-6 months | | 4 | To skeletal maturity | None | Monitor for late redislocation, cubitus valgus, synostosis and PIN recovery | PIN recovery: 90% of neuropraxias resolve by 6 months with observation, serial exams every 4-6 weeks, and a hand splint in the functional position (wrist and MCP extension). Obtain EMG/NCS and consider exploration if there is no recovery by 6 months. Return to activity: non-contact sports at about 3 months, contact sports at 4-6 months, and full unrestricted activity at around 6 months once the fracture is healed and strength is restored. Acute ORIF with anatomic reduction gives 80-85% excellent or good results; chronic reconstruction is less predictable (70-80% achieve functional motion, with a higher redislocation rate of 15-25%). Complications

Key complication patterns by Bado type - Type I (anterior): highest PIN injury rate (15-20%); best prognosis with anatomic reduction; the annular ligament is often torn (may need reconstruction); lowest stiffness risk.

• Type II (posterior): highest risk of elbow stiffness (30-40%) with loss of flexion the commonest problem; olecranon fractures common; lower PIN injury rate (5-10%).
• Type III (lateral): common in young children (2-7 years); risk of cubitus valgus from metaphyseal malunion; the ulnar fracture is often greenstick (may displace in a cast); moderate PIN injury rate (10-15%).
• Type IV (both bones): highest complication rate overall; compartment syndrome risk (5-10%); multiple nerve injuries possible; longer recovery with more stiffness.

Pathoanatomy. A Monteggia lesion is a fracture of the ulna with dislocation of the radial head. In the acute phase (0-3 weeks) the ulna fractures with apex angulation, the radial head dislocates in the direction of that apex, the annular ligament is torn or avulsed (especially in Type I), the interosseous membrane is disrupted, the radius may show plastic deformation (permanent bowing without a visible fracture line), and the PIN is stretched over the displaced radial head (a 10-20% injury rate). In the chronic phase (more than 3 weeks) the ulna begins to heal in a malunited position, the radial head remains dislocated with the annular ligament contracted or healed in an elongated position, the radial head cartilage begins to degenerate (6-12 weeks), the radiocapitellar joint becomes incongruent with possible capitellar remodelling (flattening), soft-tissue contractures develop, and a bone block may form at the radial notch preventing reduction. Biomechanics. Ulnar shortening of just 2-3 mm creates proximal translation of the radial head and anterolateral instability; plastic deformation of the radius creates a bow that prevents reduction even with anatomic ulna reduction; the annular ligament provides 60-70% of radial head stability in rotation; and loss of radiocapitellar contact increases stress on the interosseous membrane by 30-40% (which normally transmits about 80% of axial load from radius to ulna).

Outcomes by treatment type. Acute ORIF (less than 3 weeks): radial head reduction in 90-95% with anatomic ulna reduction; PIN recovery in 90% by 6 months; 85-90% achieve more than 120 degrees flexion and more than 80 degrees pronation/supination by 12 months; redislocation in 5-10% (mostly within the first 6 weeks); return to full activity in 3-6 months. Chronic reconstruction (more than 3 weeks): radial head reduction in 70-80%; annular ligament reconstruction needed in 80-90%; 70-80% achieve functional motion (some permanent limitation is common); redislocation in 15-25%; radial head excision may be needed for failed reconstruction (wait until skeletal maturity). Plate versus intramedullary fixation: a plate is more stable and allows earlier mobilisation but with greater soft-tissue trauma; an IM wire dissects less and lowers infection risk but is less stable; outcomes are similar in appropriate cases (transverse or short-oblique fractures in younger children suit an IM wire), while a plate is preferred for comminuted fractures, adolescents and revision surgery. Prognostic factors. Favourable: Bado Type I, age less than 10 years, acute presentation, anatomic ulna reduction, no PIN injury at presentation, a closed injury, and compliance with immobilisation. Unfavourable: Bado Type II (stiffness risk), age more than 12 years (approaching skeletal maturity), chronic presentation, ulnar malunion or persistent shortening, uncorrected radius plastic deformation, high-energy Type IV injuries, and multiple reduction attempts (more stiffness). There is no Level I randomised evidence comparing surgical techniques — this is a rare, heterogeneous injury — but multiple Level III-IV series and expert consensus consistently confirm that anatomic ulnar reduction is essential, radius plastic deformation must be corrected, annular ligament reconstruction is needed for chronic or unstable cases, a transarticular K-wire (if used) must be removed by 3-4 weeks, and supination immobilisation stabilises the radial head.