Paediatric Femoral Shaft Fracture — Flexible Intramedullary Nailing

Indication. A displaced, closed paediatric femoral shaft fracture in a child typically 5 to 11 years old weighing less than 50 kg that is length-stable (transverse or short-oblique midshaft) and either has unacceptable alignment after a trial of closed reduction and spica casting or is unsuitable for casting. Flexible intramedullary nailing lets the child mobilise early, avoids the morbidity of a prolonged spica, and has a union rate greater than 95 percent when the patient is correctly selected. Children less than 5 years, or stable patterns that reduce acceptably, are still managed in a spica. Acceptable alignment after closed reduction (spica is reasonable up to these limits): less than 10 degrees varus/valgus, less than 15 degrees anterior or posterior angulation, and less than 1.5 cm shortening. Beyond these, or when casting would compromise care, fix it. Assess the whole child and the whole fracture before committing. Flexible nailing only works when the fracture is length-stable. Exclude or plan for:

• Length-unstable patterns — spiral, comminuted, or long-oblique fractures where the obliquity is greater than twice the femoral diameter, or comminution involves greater than 50 percent of the circumference. These shorten and angulate under flexible nails and need submuscular plating or a rigid nail.
• Older or heavier children — above 11 years or 50 kg the complication rate (malunion, nail breakage) rises sharply; many centres default to submuscular plating or a lateral-entry rigid nail.
• Open physes with very proximal or distal fractures where nail trajectory risks physeal violation, pathological fractures through a cyst or tumour (biopsy plus alternative fixation), and active infection at the planned entry sites. Contraindicated in length-unstable patterns, in children older than 11 years or heavier than 50 kg (relative — higher failure rates), in active entry-site infection, and in pre-existing neuromuscular conditions with a high risk of nail migration (for example severe spasticity). The one decision that matters. Every flexible nail job is built on the same idea — two retrograde pre-bent nails creating opposing three-point fixation. The choice is really which fixation strategy fits the child and the pattern:

Consent specifically for the 15 to 25 percent risk of nail-end irritation or bursitis at the knee (the commonest reason to return to theatre for trimming or early removal), the planned second procedure to remove the nails at 6 to 12 months, a small risk of malunion or leg-length discrepancy, and (in length-unstable patterns treated against the grain) loss of reduction. Setup. Supine on a radiolucent fracture table or flat-top table, the injured leg prepared free or placed in traction with the contralateral leg abducted or scissored for circumferential fluoroscopic access; a small bump under the ipsilateral buttock neutralises external rotation. C-arm on the contralateral side — confirm true AP and lateral of the hip, fracture and knee are all obtainable without moving the limb, and that both entry points are visible on the same AP view before you incise. General anaesthesia with muscle relaxation for closed reduction; a femoral or fascia-iliaca block may be added for postoperative analgesia but does not replace the general. Apply longitudinal traction with the hip flexed 20 to 30 degrees and slight abduction; for shortening greater than 2 cm use 5 to 10 minutes of sustained traction or a fracture table. Judge rotation from the profile of the lesser trochanter on the AP view, compared with the contralateral side.

The goal: reduce the fracture closed, expose the distal femur through two small metaphyseal entry incisions that stay clear of the distal femoral physis, pass two pre-bent titanium elastic nails retrograde across the fracture to create opposing three-point fixation, and stabilise the child in near-anatomic alignment so they can mobilise. The exposure is laid out in full as the opening steps below.

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Rehabilitation | Phase | Timing | Immobilisation & weight bearing | Activity | |-------|--------|----------------------------------|----------| | Early | 0 to 2 weeks | Knee immobiliser or long-leg cast for comfort (under 8 years); removable brace in older children. Touch-down weight bearing for stable fractures; non- or partial weight bearing for unstable patterns until callus (3 to 4 weeks) | Finger and ankle motion; wound dry for 10 to 14 days; sutures out at 12 to 14 days | | Rehabilitation | 2 to 8 weeks | Removable splint; progressive weight bearing as callus forms (usually 4 to 6 weeks) | Active knee and hip range of motion from week 2; physiotherapy for gait and strengthening; full weight bearing by 6 to 8 weeks in stable fractures | | Return to activity | 8 weeks onward | — | Return to school at 2 to 4 weeks; sports at 3 to 6 months once radiographically united and strong | Nail removal is elective at 6 to 12 months once bridging callus is mature and remodelling has begun — earlier removal (before 6 months) risks refracture, and later removal (after 18 months) gets technically harder as bone overgrows the nail ends. Remove earlier if the nails are symptomatic; trimming a prominent end is a valid interim option. Complications

How the implant works. Each pre-bent nail contacts the cortex at three points — the entry cortex, the opposite cortex at the apex of the bend (fracture level), and the far cortex proximal or distal to the fracture. The elastic recoil of the pre-bent titanium creates continuous compression across the fracture, and balanced medial and lateral nails counteract varus/valgus and flexion/extension forces. The femoral isthmus (the narrowest point, at the junction of the proximal and middle thirds) governs nail diameter: at 8 to 12 mm in the target age group, a nail of 30 to 40 percent of that diameter is chosen. The canal widens distally into the metaphysis, which is what allows two divergent nails to be inserted without cortical perforation. Selection thresholds. The age and weight criteria are evidence-based, not arbitrary: the multicentre series of Moroz and colleagues identified 11 years and 50 kg as the inflection points, with children above these having 4.3 times higher odds of a poor outcome. Length-stable fractures are the key eligibility test — long-oblique and comminuted patterns shorten under elastic nails, and end caps only partly mitigate this.

Outcomes. In properly selected length-stable fractures, union exceeds 95 percent, with radiographic union at 6 to 10 weeks in children under 10 and return to protected full weight bearing by 4 to 8 weeks. Leg-length discrepancy greater than 1 cm occurs in less than 5 percent when the nails are of equal diameter and symmetrically pre-bent. The dominant complication is nail-end irritation (15 to 25 percent), reflecting the prominence of the nail tips at the knee rather than a failure of fixation.