A Biomechanical Study of the Stability of Titanium Elastic Nails in the Treatment of Oblique Segmental Fracture of the Femur in Children

Purpose Titanium elastic nails are widely used in the treatment of femoral shaft fractures in children. The standard technique employs the retrograde insertion of two curved nails, with the apex of the curve at the fracture site. This study examines the biomechanical stability of this configuration of titanium elastic nails in segmental femoral fractures, an injury which is often highenergy and therefore inherently unstable. The stability of a new nailing technique is also tested, using an additional third nail inserted antegrade. Methods A model of a segmental femoral fracture was created in four synthetic femora. Two were fixed with the standard two retrograde nails and two with the third antegrade nail. A fifth was used as a control. Each was tested with axial, torsional and bending loads and the deflection measured. Result Minimal deviation of the models occurred under physiological loads in all forms of loading. There was statistically significant increased torsional and bending stiffness using the three-nail technique compared with the standard two-nail technique. Conclusion Titanium elastic nails in the standard two-nail retrograde system can provide a stable mechanical construct for the fixation of segmental femoral fracture. The use of a third nail inserted antegrade increased the stability in bending and torsion, however theoretically it carries a potential risk of splitting the femoral canal and creating subtrochantric fracture especially if the canal fill exceeds 80%. Accordingly we do not recommend the use of the three-nail system described in this study as a routine choice.Clinically Titanium elastic nail provide sufficient stability to avoid prolonged period in traction. Post-operative bed rest might be recommended to allow the development of early callus formation that further increase the stability of the fracture and allow weight bearing.