Exchange Intramedullary Nailing for Long-Bone Nonunion

Surgical Indications

Absolute Indications

• Aseptic hypertrophic or oligotrophic diaphyseal nonunion of the femur or tibia with a viable biological response after exclusion of infection
• Failed or undersized index intramedullary nail with persistent pain, instability or lack of radiographic progression at greater than 6-9 months
• Nonunion with acceptable alignment (less than 5 degrees varus/valgus, less than 10 degrees procurvatum/recurvatum) that can be maintained during exchange

Relative Indications

• Atrophic nonunion with poor biology when combined with bone grafting or adjunctive stimulation
• Nonunion with moderate bone loss (less than 1 cm) where reaming debris can provide local autograft
• Patient preference for a minimally invasive biological solution before considering open plating or transport

Contraindications

Absolute:

• Active or suspected infection (elevated inflammatory markers, draining sinus, positive cultures) — requires staged debridement and antibiotic management
• Severe bone loss greater than 2-3 cm or segmental defect requiring bone transport or Masquelet technique
• Gross malalignment or malrotation that cannot be corrected through the existing nail tract

Relative:

• Poor soft-tissue envelope or active ulceration over the proposed nail tract
• Severe osteoporosis or narrow canal diameter precluding adequate reaming and fill
• Non-compliant patient unable to follow protected weight-bearing protocol

Evidence for Exchange Nailing

Rationale and Biological Effect

• Reaming to a larger diameter increases the moment of inertia and bending stiffness of the implant (proportional to the fourth power of the radius)
• Reaming debris provides local autograft containing osteoprogenitor cells, growth factors and a scaffold that stimulates the healing response in viable nonunions
• The procedure simultaneously addresses both the mechanical and biological requirements for union in the majority of aseptic cases

Femoral versus Tibial Outcomes

• Femoral exchange nailing consistently achieves union rates greater than 90 percent in aseptic hypertrophic nonunions when infection is excluded and adequate stability is obtained
• Tibial exchange nailing achieves union in 70-85 percent of cases; the lower rate is attributed to poorer soft-tissue envelope, dependent blood supply and higher incidence of open injuries
• A systematic review of exchange nailing for femoral nonunion reported mean time to union of 6-8 months with low complication rates when performed for aseptic cases

Comparison with Alternative Techniques

• Plating with compression offers direct visualisation and the ability to apply absolute stability and bone graft but requires extensive exposure and carries higher infection risk in previously operated limbs
• Bone transport (Ilizarov or monolateral) is preferred when bone loss exceeds 2-3 cm or when the soft-tissue envelope is severely compromised
• The Masquelet induced-membrane technique is an alternative for large defects but requires two stages and is more invasive than exchange nailing for contained nonunions

Key Evidence

Relevant Surgical Anatomy for Exchange Nailing

Femoral Diaphysis and Nail Tract

• The femoral isthmus is the narrowest portion of the medullary canal, typically at the junction of the middle and distal thirds
• The original nail tract must be thoroughly cleared of fibrous tissue and sclerotic bone before reaming
• The greater trochanter and piriformis fossa are the entry points for antegrade femoral nailing; the intercondylar notch for retrograde
• The profunda femoris artery and its perforators lie medial to the proximal femur — at risk during proximal locking or if the nail perforates medially

Tibial Diaphysis and Nail Tract

• The tibial medullary canal is triangular in cross-section proximally, becoming more circular distally
• The anteromedial surface is subcutaneous — the most common site for open fractures and subsequent nonunion
• The popliteal artery and tibial nerve lie posterior to the proximal tibia; the common peroneal nerve winds around the fibular neck laterally
• The anterior tibial artery passes through the interosseous membrane at the proximal third — vulnerable during distal locking or reaming

Safe Intervals and Structures at Risk

• Anterolateral approach to the femur (for exposure if needed): between vastus lateralis and biceps femoris; the perforating branches of the profunda femoris are at risk
• Anteromedial approach to the tibia: between tibialis anterior and the medial border of the tibia; the saphenous vein and nerve are medial and must be protected
• During reaming, the radial nerve (for humerus, not relevant here) and the sciatic nerve (proximal femur) are at risk if the entry point is misplaced

Related Approaches

• The anteromedial approach to the tibial shaft is used when adjunctive plating or bone grafting is required
• The anterolateral approach to the femoral shaft allows access to the lateral cortex for plating or bone grafting if exchange nailing alone is insufficient

Positioning and Setup

Patient Positioning

• Supine on a radiolucent table with the affected limb free-draped and the contralateral limb also accessible for comparison
• For femoral nailing a traction table or manual traction with a femoral distractor may be used; ensure the perineal post is well padded
• For tibial nailing a bump under the ipsilateral hip helps with rotational control; the foot is left free for length assessment
• Image intensifier positioned on the contralateral side with the C-arm able to obtain anteroposterior and lateral views of the entire bone

Equipment and Implants

• Extraction set for the existing nail (extraction bolt, slap hammer, broken-screw removal instruments)
• Flexible reamers with sharp heads, starting from the diameter of the removed nail and increasing in 0.5 mm increments
• Exchange nail: typically 1.5-2 mm larger in diameter than the removed nail, same or longer length, with multiple proximal and distal locking options
• Intraoperative culture swabs, frozen section if infection suspected, and autograft harvesting instruments if needed

Step-by-Step Operative Technique

1. Exposure and Nail Removal

• Make a small incision over the original entry point (greater trochanter or tibial tuberosity) and expose the proximal nail end
• Remove proximal locking screws first, then attach the extraction device and remove the nail with steady traction and gentle rotation
• If the nail is incarcerated, use a broken-nail extraction kit or consider creating a cortical window
• Send the removed nail and any surrounding tissue for culture; obtain intraoperative frozen section if any concern for infection

2. Canal Preparation and Reaming

• Pass a guide wire through the existing tract into the distal fragment under image guidance, confirming it lies in the centre of the canal
• Sequentially ream the canal starting at the diameter of the removed nail and advancing in 0.5 mm increments until cortical chatter is obtained
• Ream at least 1.5-2 mm greater than the removed nail diameter to achieve adequate fill and deposit reaming debris at the nonunion site
• Irrigate copiously during reaming to reduce thermal necrosis and fat embolism risk; monitor for desaturation or rising end-tidal CO2

3. Reduction and Nail Insertion

• Reduce the nonunion site using traction, percutaneous clamps or a femoral distractor; correct any angular or rotational deformity
• Insert the new larger-diameter nail over the guide wire, ensuring it passes the nonunion site without creating a new fracture
• Confirm length and alignment with full-length images or comparison to the contralateral limb using the lesser trochanter profile or cortical step sign

4. Interlocking and Stability

• Lock the nail statically with at least two proximal and two distal screws; use a third screw if bone quality is poor
• For femoral nails, ensure the proximal locking screws engage the calcar or greater trochanter as appropriate for the nail design
• For tibial nails, avoid the popliteal vessels during proximal locking and the anterior tibial artery during distal locking
• Apply compression across the nonunion if possible by using a compression screw or back-slapping the nail before final distal locking

5. Adjuncts and Closure

• If the nonunion site remains mobile after nail insertion, consider percutaneous injection of reaming debris or autograft from the reamer
• Close the entry-point incision in layers; apply a sterile dressing and a well-padded splint or brace for comfort
• Document the final nail diameter, length, and number of locking screws in the operative note

Immediate Postoperative Protocol

Weight-Bearing and Mobilisation

• Touch weight-bearing for the first 2-4 weeks in most cases; progress to partial weight-bearing (20-30 kg) once pain allows
• Full weight-bearing is permitted when there is radiographic evidence of callus formation, typically at 6-12 weeks
• Tibial nonunions require longer protected weight-bearing than femoral cases because of the higher mechanical stress and poorer biology

Wound and Infection Surveillance

• Monitor the wound at 48 hours and 2 weeks; any erythema, drainage or fever prompts urgent CRP and wound swab
• Perioperative antibiotics are continued for 24-48 hours unless cultures were positive, in which case a full course is completed
• Patients with diabetes or immunosuppression require extended monitoring for wound complications

Pain and Swelling Management

• Elevation of the limb above heart level for the first 48-72 hours
• Multimodal analgesia including paracetamol, NSAIDs (if not contraindicated) and short-course opioids
• Ice and compression help reduce swelling; avoid circumferential dressings that restrict venous return

Rehabilitation Milestones

0-6 Weeks

• Gentle active and active-assisted range-of-motion exercises for knee and ankle
• Isometric quadriceps and hamstring exercises to maintain muscle tone
• Progressive weight-bearing as tolerated under physiotherapy supervision

6-12 Weeks

• Begin resistance exercises and gait training once partial weight-bearing is comfortable
• Monitor for signs of hardware loosening or increasing pain that may indicate delayed union

3-6 Months

• Full weight-bearing when bridging callus is visible on two radiographic views
• Functional testing (single-leg stance, step-up) before return to work or sport
• Smoking cessation counselling is critical — continued smoking doubles the risk of persistent nonunion

Adjunctive Measures

• Bone stimulators (low-intensity pulsed ultrasound or pulsed electromagnetic fields) may be considered for high-risk tibial nonunions after 3 months
• Nutritional optimisation (vitamin D, calcium, protein) and glycaemic control in diabetics improve healing potential
• Dynamisation (removal of one proximal or distal screw) is considered only after 3-4 months if there is no progression and the nonunion appears axially stable

Intraoperative Complications

Fat Embolism and Pulmonary Effects

• Reaming of the femoral canal can produce fat emboli, especially in polytrauma patients with recent chest injury
• Prevention: sharp reamers, slow advancement, generous irrigation, continuous monitoring of oxygen saturation and end-tidal CO2
• Treatment: supportive ventilation, fluid resuscitation, consider delaying exchange nailing in high-risk patients

Iatrogenic Fracture or Perforation

• Occurs when the reamer or nail deviates from the canal or encounters sclerotic bone at the nonunion
• Prevention: careful guide-wire placement, sequential reaming, and image confirmation at each step
• Management: cerclage wiring, longer nail spanning the fracture, or conversion to plating

Neurovascular Injury

• The sciatic nerve (proximal femur), common peroneal nerve (proximal tibia/fibula), and anterior tibial artery (distal tibia) are at risk
• Prevention: careful portal placement, gentle retraction, and avoidance of excessive traction on the limb

Early Postoperative Complications

Infection

• Occurs in 2-5 percent of apparently aseptic cases; may present as wound erythema, sinus formation or hardware loosening
• Management: urgent debridement, cultures, intravenous antibiotics, and conversion to a staged protocol with antibiotic spacer

Hardware Failure or Nail Breakage

• Rare with modern larger-diameter nails but can occur at the nonunion site if rotational stability is inadequate
• Prevention: static interlocking with multiple screws; protected weight-bearing until union

Late Complications and Persistent Nonunion

Persistent Nonunion

• Occurs in 5-10 percent of femoral and 15-30 percent of tibial exchange nailings
• Evaluation: repeat infection workup, CT to assess bone loss and stability, smoking and metabolic screening
• Management options:
  • Repeat exchange nailing with further reaming and bone grafting
  • Compression plating with autograft
  • Bone transport for defects greater than 2 cm
  • Masquelet induced-membrane technique for large defects with poor soft tissue

Malalignment and Leg-Length Discrepancy

• Rotational malalignment greater than 15 degrees or length discrepancy greater than 1 cm requires corrective osteotomy
• Prevention: meticulous intraoperative comparison with the contralateral limb

Chronic Pain and Functional Limitation

• May result from muscle scarring, joint stiffness, or neuropathic pain
• Management: structured physiotherapy, pain management referral, and realistic expectation setting preoperatively