title: Angular stability potentially permits fewer locking screws compared with conventional locking in intramedullary nailed distal tibia fractures: a biomechanical study.
abstract: OBJECTIVE
  To compare mechanical stability of angle-stable locking construct with four screws with conventional five screw locking in intramedullary nailed distal tibia fractures under cyclic loading.
  
  
  METHODS
  Ten pairs of fresh-frozen human cadaveric tibiae were intramedullary nailed and assigned to either an angle-stable locking construct consisting of four screws or conventional five-screw locking. After simulating an unstable distal two-fragmental 42-A3.1 fracture, the specimens were mechanically tested under quasistatic and cyclic sinusoidal axial and torsional loading.
  
  
  RESULTS
  Bending stiffness of the angle-stable and the conventional fixation was 644.3 N/° and 416.5 N/°, respectively (P = 0.075, power 0.434). Torsional stiffness of the angle-stable locking (1.91 Nm/°) was significantly higher compared with the conventional one (1.13 Nm/°; P = 0.001, power 0.981). Torsional play of the angle-stable fixation (0.08°) was significantly smaller compared with the conventional one (0.46°; P = 0.002, power 0.965). The angle-stable locking revealed significantly less torsional deformation in the fracture gap after one cycle (0.74°) than the conventional one (1.75°; P = 0.005, power 0.915) and also after 1000 cycles (angle-stable: 1.56°; conventional: 2.51°; P = 0.042, power 0.562). Modes of failure were fracture of the distal fragment, loosening of distal locking screws, nail breakage, and their combination, equally distributed between the groups (P = 0.325).
  
  
  CONCLUSIONS
  Both the angle-stable locking technique using four screws and conventional locking consisting of five screws showed high biomechanical properties. Hence, angle-stable locking reflects a potential to maintain fixation stability while reducing the number of locking screws compared with conventional locking in intramedullary nailed unstable distal tibia fractures.
authors.affiliation: AO Research Institute Davos, AO Foundation, Davos, Switzerland. boyko.gueorguiev@aofoundation.org
authors.forename: Boyko
authors.initials: B
authors.lastname: Gueorguiev
authors.forename: Ben
authors.initials: B
authors.lastname: Ockert
authors.forename: Karsten
authors.initials: K
authors.lastname: Schwieger
authors.forename: Dirk
authors.initials: D
authors.lastname: Wähnert
authors.forename: Matthew
authors.initials: M
authors.lastname: Lawson-Smith
authors.forename: Markus
authors.initials: M
authors.lastname: Windolf
authors.forename: Karl
authors.initials: K
authors.lastname: Stoffel
mesh_terms: D000368:Aged; D001858:Bone Nails; D002102:Cadaver; D055119:Elastic Modulus; D019544:Equipment Failure Analysis; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D013718:Tensile Strength; D013978:Tibial Fractures / Q000503:physiopathology* / Q000601:surgery*; D016896:Treatment Outcome