Courtesy: Dr. Sandeep Patwardhan, Dr Ashok Shyam, Ortho TV

 

Pediatric Radial Neck Fractures & Post-Traumatic Proximal Radioulnar Synostosis

Pitfalls in Pediatric Radial Neck Fracture Management

• The High Vulnerability Zone: Fractures through the radial neck in skeletally immature patients (ages 7 to 9) carry significant risks of severe complications, specifically proximal radioulnar synostosis (cross-union) and complete loss of forearm pronosupination.

• The Hazards of Open Reduction:

  • Formal open reduction of a pediatric radial neck fracture significantly increases the risk of periarticular scarring, devascularization of the radial head, and heterotopic cross-union.

  • Direct surgical exposure strips periosteum, introduces surgical hematoma, and is considered a primary contributor to post-traumatic synostosis.

• The Hidden Risk in Closed Management:

  • Non-operative management or closed reduction in a cast is generally preferred over open surgery, but it is not without risk.

  • Concomitant high-energy tear or rupture of the proximal interosseous membrane/capsular structures extending toward the ulna can cause a confluent hematoma that bridges the radius and ulna.

  • Subsequent hematoma ossification can produce a complete radioulnar synostosis even after non-operative treatment in plaster.

• Reduction Strategy: Percutaneous reduction techniques (e.g., Métaizeau intramedullary pin manipulation or percutaneous K-wire joysticking) are favored over open reduction when acceptable closed reduction cannot be achieved, minimizing local periosteal disruption.

Post-Traumatic vs. Congenital Synostosis

• Congenital Radioulnar Synostosis:

  • Arises from a failure of longitudinal segmentation during embryogenesis.

  • Characterized by primary hypoplasia/absence of the proximal radioulnar joint (PRUJ), abnormal osseous architecture, and contracted soft-tissue envelopes.

  • Simple surgical resection typically fails and has high recurrence rates; rotational osteotomy to place the forearm in a functional position is often preferred.

• Post-Traumatic Radioulnar Synostosis:

  • True secondary osseous bridge formation across a previously normal proximal radioulnar joint.

  • Distinct from congenital forms because articular architecture and soft-tissue envelopes are intact prior to injury.

  • Resection of the synostosis mass can successfully restore active pronosupination when the bone bridge is quiescent and mature.

Surgical Protocol: Synostosis Resection & Interposition Arthroplasty

• Timing of Intervention:

  • Surgical excision is strictly indicated only when the post-traumatic ossification is completely mature and quiescent (cold on biological monitoring, well-corticated on plain radiographs and CT).

• Preoperative Workup & Advanced Imaging:

  • Multiplanar 3D CT imaging is mandatory to map and quantify the exact size, orientation, and longitudinal extent of the fusion mass (e.g., measuring bridge width, typically $\approx 1\text{ cm}$).

• Surgical Approach & Technique:

  • Approach: Posterior/posterolateral exposure to safely access the proximal radius and ulna while protecting the posterior interosseous nerve (PIN).

  • Excision: Isolate the radial head and neck; completely resect the synostosis bridge down to normal cortical margins on both the radius and ulna.

  • Intraoperative Assessment: Confirm immediate, full mechanical restoration of active/passive forearm pronation and supination on the table before reconstruction.

• Interposition Fat Grafting:

  • Excision alone leaves two raw, bleeding cancellous surfaces adjacent to each other, carrying an unacceptably high risk of recurrent cross-union.

  • Harvest an autologous inert fat graft (e.g., from the local triceps area or subcutaneous tissue).

  • Pack and interpose the fat graft securely into the radioulnar interval.

  • Secure the graft with anchoring sutures to prevent migration or washout when releasing the tourniquet.

• Postoperative Rehabilitation:

  • Initiate aggressive, early active and active-assisted range-of-motion physiotherapy within the first few postoperative weeks to prevent recurrent adhesion formation.

Classification & Clinical Summary

• Anatomical Levels: Post-traumatic pediatric cross-unions are classified topographically by location:

  • Proximal (involving the radial neck/bicipital tuberosity and proximal ulna).

  • Diaphyseal (middle third of the forearm).

  • Distal (distal radioulnar joint / metaphyseal region).

• Core Takeaways:

  • Avoid unnecessary open reduction of radial neck fractures in children due to the high risk of cross-union.

  • Differentiate post-traumatic from congenital synostosis; post-traumatic lesions have viable joint potential.

  • Quiescent post-traumatic proximal synostosis can be managed with bridge resection, autologous interposition fat grafting, and early aggressive postoperative mobilization to restore pronosupination.