Paediatric Femoral Shaft Fracture — Flexible Intramedullary Nailing

Surgical Indications

Absolute Indications

• Length-stable transverse or short-oblique midshaft femoral fractures in children 5-11 years weighing less than 50 kg
• Closed or Gustilo-Anderson grade I open fractures amenable to closed reduction
• Fractures with unacceptable alignment after closed reduction and spica casting (greater than 10 degrees varus/valgus, greater than 15 degrees anterior/posterior angulation, greater than 1.5 cm shortening)

Relative Indications

• Polytrauma patient where early mobilisation reduces pulmonary and skin complications
• Multiple long-bone fractures where spica casting would compromise care
• Patient or family preference for surgical stabilisation over prolonged casting

Contraindications

Absolute:

• Length-unstable fracture patterns (spiral, comminuted, long-oblique greater than twice the femoral diameter at the fracture site)
• Children older than 11 years or weighing greater than 50 kg (higher malunion and implant failure rates)
• Active infection at the planned entry sites
• Pre-existing neuromuscular conditions with high risk of nail migration (e.g. severe spasticity)

Relative:

• Open physes with very proximal or distal fractures where nail trajectory risks physeal violation
• Pathological fractures through bone cysts or tumours (consider biopsy and alternative fixation)
• Severe soft-tissue injury requiring delayed definitive fixation

Evidence for Flexible Intramedullary Nailing

Outcomes in Length-Stable Fractures

• Union rates exceed 95 percent when proper patient selection and technique are followed
• Average time to radiographic union 6-10 weeks in children under 10 years
• Return to full weight bearing typically 4-8 weeks with protected progression
• Leg-length discrepancy greater than 1 cm occurs in less than 5 percent when both nails are of equal diameter and symmetrically pre-bent

Comparison with Alternative Treatments

Key Evidence

Relevant Surgical Anatomy for Retrograde Flexible Nailing

Distal Femoral Metaphysis and Physis

• The distal femoral physis is the most active growth plate in the lower limb, contributing 70 percent of femoral length and 40 percent of lower-limb length
• The physis lies at the level of the adductor tubercle medially and approximately 1 cm proximal to the superior pole of the patella laterally when the knee is flexed 90 degrees
• Entry points must be placed 1.5-2 cm proximal to the physis in the metaphyseal flare to avoid physeal injury and subsequent growth disturbance or angular deformity
• The medial metaphysis is narrower; the lateral metaphysis provides a wider safe corridor

Medullary Canal Geometry

• The femoral isthmus (narrowest point) lies at the junction of the proximal and middle thirds
• Canal diameter at the isthmus in a 6-10 year old typically measures 8-12 mm; nail diameter is chosen so each nail occupies 30-40 percent of this diameter
• The canal widens distally into the metaphysis, allowing divergent nail insertion without cortical perforation

Three-Point Fixation Principle

• Each pre-bent nail contacts the cortex at three points: the entry cortex, the opposite cortex at the fracture level (apex of bend), and the far cortex proximal or distal to the fracture
• The elastic recoil of the pre-bent titanium creates continuous compression across the fracture site
• Balanced medial and lateral nails counteract varus/valgus and flexion/extension forces; unequal nails or asymmetric bends produce malalignment

Neurovascular Structures at Risk

• The femoral artery and vein lie anteromedial in the distal thigh and are protected by the vastus medialis during medial approach
• The sciatic nerve and its branches are posterior and protected by the hamstring compartment
• The saphenous nerve and vein cross the medial distal femur superficially; they are at risk during medial incision and retraction
• The lateral femoral cutaneous nerve is not at risk in this approach

Muscle Intervals

• Medial approach: between vastus medialis (anterior) and sartorius/adductor (posterior); the interval is relatively avascular
• Lateral approach: through the iliotibial band and vastus lateralis; the lateral supracondylar ridge provides a palpable landmark

Positioning and Preparation

Patient position: Supine on a radiolucent fracture table or flat-top table. The injured leg is prepared free or placed in traction. Contralateral leg is abducted or scissored to allow circumferential fluoroscopic access. A small bump under the ipsilateral buttock helps neutralise external rotation.

Fluoroscopy: C-arm positioned on the contralateral side. True AP and lateral views of the hip, fracture, and knee must be obtainable without moving the limb. Confirm both entry points are visible on the same AP view before incision.

Anaesthesia: General anaesthesia with muscle relaxation for closed reduction. Regional blocks (femoral or fascia iliaca) may be added for postoperative analgesia but do not replace the need for general anaesthesia in children.

Traction and reduction: Apply longitudinal traction with the hip flexed 20-30 degrees and slight abduction. For shortening greater than 2 cm, 5-10 minutes of sustained traction or use of a fracture table may be required. Rotational alignment is judged by the profile of the lesser trochanter on the AP view compared with the contralateral side.

Implant selection: Measure canal diameter at the isthmus on the pre-operative or intra-operative radiograph. Choose two titanium elastic nails of equal diameter, each 30-40 percent of canal diameter. Have end caps available for all cases.

Operative Steps — Retrograde Flexible Intramedullary Nailing

Step 1: Closed Reduction and Temporary Stabilisation

Confirm fracture pattern and length stability on fluoroscopy. Perform closed reduction with traction, abduction, and rotation. If reduction cannot be maintained, pass a percutaneous clamp or use a small medial incision to assist reduction before nail insertion. Do not proceed with nailing if anatomic reduction cannot be achieved.

Step 2: Medial and Lateral Entry Point Incisions

Make 2-3 cm longitudinal incisions over the medial and lateral distal femoral metaphysis. The medial incision is centred 1.5-2 cm proximal to the adductor tubercle; the lateral incision is 1.5-2 cm proximal to the lateral femoral condyle flare. Incise the fascia and split the muscle fibres down to bone.

Step 3: Create Entry Holes and Pre-bend Nails

Using a 3.2 mm drill or awl, create two entry holes in the metaphysis, directed proximally at 30-40 degrees to the long axis and slightly anterior to avoid the posterior cortex. The holes should be 1 cm apart in the sagittal plane to prevent nail collision. Enlarge each hole with a curved awl or small rongeur to allow easy nail passage.

Pre-bend both nails to three times the canal diameter using a nail bender. The apex of the bend should be at the expected fracture level when the nail is fully seated. Ensure the bends are symmetric and in the same plane.

Step 4: Insert the First Nail (Usually Medial)

Load the first nail (medial) onto the insertion handle. Advance the nail by hand or with gentle mallet taps through the entry hole, across the fracture, and into the proximal fragment. The nail should slide easily; resistance indicates wrong trajectory or incomplete reduction. Rotate the nail so the apex of the bend faces the opposite cortex at the fracture site.

Advance the nail until its tip reaches the level of the greater trochanter or femoral neck junction on the AP view. Confirm on lateral view that the nail has not perforated the anterior cortex proximally.

Step 5: Insert the Second Nail (Lateral) and Achieve Balanced Fixation

Insert the lateral nail through its separate entry hole using the same technique. The two nails should cross at the fracture site in opposite directions, creating balanced three-point fixation. Confirm on AP and lateral fluoroscopy that both nails have reached the proximal metaphysis without crossing the physis or perforating the cortex.

If the fracture is length-unstable, apply end caps to both nail ends now. The end caps are screwed onto the threaded nail tips and sit against the metaphyseal cortex, preventing shortening.

Step 6: Final Reduction Check and Wound Closure

Obtain full-length AP and lateral radiographs of the femur. Acceptable alignment: less than 5 degrees varus/valgus, less than 10 degrees anterior/posterior angulation, less than 5 degrees rotation, less than 1 cm shortening. If alignment is unacceptable, remove one nail, re-reduce, and re-insert.

Trim the nail ends flush with the metaphyseal cortex or leave 5 mm proud with end caps. Close the fascia and skin in layers. Apply a light dressing and a knee immobiliser or long-leg cast for comfort in younger children.

Post-operative Protocol

Early Phase (Day 0-14)

• Immobilisation: Knee immobiliser or long-leg cast for comfort in children under 8 years; removable brace in older children
• Weight bearing: Touch-down weight bearing for length-stable fractures; non-weight bearing or partial for unstable patterns until callus appears (usually 3-4 weeks)
• Analgesia: Paracetamol, NSAIDs, and short course of oral opioids; regional catheter if placed intra-operatively
• Wound care: Keep incisions dry for 10-14 days; suture removal at 12-14 days

Rehabilitation Phase (2-8 Weeks)

• Progressive weight bearing as callus forms on radiographs (usually 4-6 weeks)
• Active knee and hip range-of-motion exercises from week 2
• Physical therapy for gait training and strengthening
• Full weight bearing typically achieved by 6-8 weeks in stable fractures

Return to Activity

• Return to school: 2-4 weeks
• Sports: 3-6 months after radiographic union and full strength
• Nail removal: elective at 6-12 months once bridging callus is mature and remodelling has begun; earlier if symptomatic irritation

Special Case: Length-Unstable Fractures

Decision-Making

Length-unstable fractures (spiral, comminuted, long-oblique) have a 20-30 percent risk of shortening or angulation when treated with flexible nails alone. Options include:

• Add end caps to both nails and protect weight bearing for 4-6 weeks
• Supplement with external fixation for 4-6 weeks
• Convert to submuscular plating (preferred in most centres)

Technique Modification When Using Flexible Nails

• Pre-bend nails more aggressively to increase elastic force
• Ensure at least 60-70 percent canal fill
• Apply end caps before final reduction check
• Consider a third small-diameter nail if space permits (rarely used)

Special Case: Children Near Age/Weight Thresholds

10-12 Years or 45-55 kg

These borderline patients have higher complication rates with flexible nailing. Decision factors:

• Fracture stability: length-stable patterns may still be suitable
• Body habitus: thin children tolerate nails better than obese children of same weight
• Surgeon experience and family preference
• Many centres now default to submuscular plating for all children older than 10 years

Alternative Fixation in Older Children

• Submuscular plating: any age, any pattern, immediate weight bearing, lower malunion rate
• Lateral-entry rigid intramedullary nail: greater than 11 years, greater than 50 kg, avoids proximal femoral physis and AVN risk of piriformis entry