title: Biomechanical analysis of a synthetic femur spiral fracture model: Influence of different materials on the stiffness in flexible intramedullary nailing.
abstract: BACKGROUND
  Flexible intramedullary nail fixation of dislocated diaphyseal femur fractures has gained wide acceptance for children and adolescents with open physes. Studies with a special emphasis on complications reveal frequent problems regarding stability, usually in complex fracture types such as spiral fractures and in older children weighing >40kg. This biomechanical study analyses how much the material of the nails influences the stiffness in a synthetic bone model.
  
  
  METHODS
  Twenty-four composite grafts (Sawbones®, 4th generation, medullar canal of 10mm) with an identical spiral fracture were used in three configurations of eight grafts. Elastic stable intramedullary nailing was performed in a retrograde C-shaped manner with two nails of equal size (2×3.5mm). Close contact of the fragments could be achieved. We compared Group A (steel nails) with Group B and C (two types of titanium nails). All specimens underwent 4-point bending, torsion and axial compression in the 0° and 9° positions, and the results were analysed.
  
  
  RESULTS
  Group A (steel nails) revealed a significantly higher stiffness in all directions than Group B. Apart from compression in the 9° position this steel nail fixation showed significant higher stiffness than titanium nails of Group C. Comparing Group B and C did not show an systematic difference.
  
  
  CONCLUSIONS
  In this biomechanical study with composite artificial bones the use of steel Nails demonstrated the highest stiffness in our model when compared to two different titanium nail configurations. Apart from in cases of known allergy or planned MRI-examinations our results and data from the literature question the use of titanium nails.
authors.affiliation: Department of Paediatric Surgery, University Hospital Luebeck, Ratzeburger Allee 160, Luebeck, Germany. kaiser@medinf.mu-luebeck.de
authors.forename: M M
authors.initials: MM
authors.lastname: Kaiser
authors.forename: L M
authors.initials: LM
authors.lastname: Wessel
authors.forename: G
authors.initials: G
authors.lastname: Zachert
authors.forename: C
authors.initials: C
authors.lastname: Stratmann
authors.forename: R
authors.initials: R
authors.lastname: Eggert
authors.forename: N
authors.initials: N
authors.lastname: Gros
authors.forename: M
authors.initials: M
authors.lastname: Schulze-Hessing
authors.forename: B
authors.initials: B
authors.lastname: Kienast
authors.forename: M
authors.initials: M
authors.lastname: Rapp
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D001858:Bone Nails; D001842:Bone and Bones / Q000473:pathology; D002648:Child; D004548:Elasticity; D005264:Femoral Fractures / Q000601:surgery; D005269:Femur / Q000601:surgery; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation / Q000379:methods*; D050723:Fractures, Bone / Q000473:pathology; D006801:Humans; D016268:Internal Fixators; D008279:Magnetic Resonance Imaging / Q000379:methods; D013232:Steel / Q000737:chemistry; D013314:Stress, Mechanical; D014025:Titanium / Q000737:chemistry
chemical_list: D013232:Steel; D014025:Titanium