Unusual Complication of Flexible Intramedullary Nail in Pediatric Femoral Shaft Fracture

Background of the Study: Femoral shaft fracture is the most common pediatric injury requiring hospitalization. For children less than 5 years old, non-surgical approach is recommended. For pediatric patients 5 - 14 years old, the most common mode of treatment is flexible intramedullary nailing with a known complication of pain at post-op site, inflammatory reaction/bursitis at the entry site, superficial and deep infection, knee synovitis, knee stiffness, leg length discrepancy, proximal nail migration, angulation or malunion, delayed and non-union, implant breakage. This study aims to present a rare complication of a femoral fracture fixed with flexible intramedullary nail. Methodology: We report the outcome of a 12-year-old male with peri implant fracture of the left femur. He underwent removal of plates and screws and subsequently fixed with flexible intramedullary nails. Patient was followed up at 1, 3, 7, and 10 months post-operatively. Varus-valgus, sagittal angulation, and limb shortening were measured pre- and post-operatively. Complications were recorded on each visit. Results: Pre-operative varus angulation was 10？, pro-curvatum of 55？ with limb shortening of 4 cm. Postoperatively, varus was maintained to 10？ but pro-curvatum was corrected to 4？ and limb shortening was reduced to 1 cm. However, after 1 month the varus angulation increased to 30？ while maintaining sagittal pro-curvatum. Limb shortening also increased to 2 cm. New bone formation started to appear along the mechanical axis of the left femur which is apparent at 3 months post-op and pro-curvatum increased to 20？. At 7 and 10 months post-op no signs of union was noted at the fracture site but the callus formation along the mechanical axis gradually matured and appeared as a new femoral shaft. Conclusion: Formation of new bone in response to unstable flexible intramedullary fixation in pediatric femoral shaft fracture is a very rare complication.