Biomechanical analysis of a synthetic femoral spiral fracture model: Do end caps improve retrograde flexible intramedullary nail fixation?

Abstract

Abstract Background Elastic Stable intramedullary Nailing (ESIN) of dislocated diaphyseal femur fractures has become an accepted method for the treatment in children and adolescents with open physis. Studies focused on complications of this technique showed problems regarding stability, usually in complex fracture types such as spiral fractures and in older children weighing > 40 kg. Biomechanical in vitro testing was performed to evaluate the stability of simulated spiral femoral fractures after retrograde flexible titanium intramedullary nail fixation with and without End caps. Methods Eight synthetic adolescent-size femoral bone models (Sawbones® with a medullar canal of 10 mm and a spiral fracture of 100 mm length identically sawn by the manufacturer) were used for each group. Both groups underwent retrograde fixation with two 3.5 mm Titanium C-shaped nails inserted from medial and lateral entry portals. In the End Cap group the ends of the nails of the eight specimens were covered with End Caps (Synthes Company, Oberdorf, Switzerland) at the distal entry. Results Beside posterior-anterior stress (4.11 Nm/mm vs. 1.78 Nm/mm, p Conclusion In this biomechanical study the use of End Caps did not improve the stability of the intramedullary flexible nail osteosynthesis.

Keywords

• Elastic stable intramedullary nailing
• ESIN
• Flexible intramedullary nails
• biomechanical testing
• femoral shaft fracture
• End Caps
• Adolescents
• Children