title: Fracture strain and stability with additional locking screws in intramedullary nailing: a biomechanical study.
abstract: BACKGROUND
  We studied the effect of additional locking screws on fracture strain and stability in tibial intramedullary nailing.
  
  
  METHODS
  We drilled an additional diaphyseal locking hole into 8-mm solid tibial nails 185 mm from the proximal end of the nail, and locked it proximally and distally. An osteotomy was produced 4.5 cm distal to the additional hole, and the construct loaded axially, in flexion, extension, and torsion. The nails were also tested for their fatigue strength.
  
  
  RESULTS
  With the additional locking screw, strain increased proximally during loading in neutral and flexion. Strain decreased on loading in extension. The extra locking screw decreased strain close to the osteotomy site in all loading positions. A significant reduction in angular motion at the osteotomy site occurred with the addition of the extra locking screw. The nails survived the fatigue test, although the stress increased around the additional locking hole
  
  
  CONCLUSIONS
  Nails with additional locking options, by altering strain and motion at the fracture site, may have the clinical potential to affect fracture healing.
authors: Department of Trauma and Orthopaedic Surgery, Keele University School of Medicine, Staffordshire, England.
authors: Murali K
authors: MK
authors: Sayana
authors: Benjamin J
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