title: Pediatric supracondylar humerus fractures: effect of bone-implant interface conditions on fracture stability.
abstract: BACKGROUND
  Closed reduction and percutaneous fixation with Kirschner wires (KWs) is the standard of care of pediatric supra-condylar humerus fractures (SCHFs). Failure modes leading to loss of reduction are not clear and have not been quantified. Multiple factors may weaken the KW-bone interface bonding conditions. To the best of our knowledge, the possible effect of this decrease on different KW configurations and fracture stability has never been studied.
  
  
  OBJECTIVE
  To investigate the effect of bone-KW friction conditions on SCHF post-operative mechanical stability and to formulate clinical guidelines for KW configuration under different conditions.
  
  
  METHODS
  Finite element-based model of a fixated SCHF was used to simulate structure stability for two lateral divergent versus crossed lateral and medial KW configurations under varying KW-bone friction conditions.
  
  
  RESULTS
  Finite element simulations demonstrated that crossed KWs provide superior stability compared with the divergent configuration when KW-bone bonding is compromised. When KW-bone bonding conditions are adequate, crossed and divergent KW configurations provide similar, sufficient fracture stability.
  
  
  CONCLUSIONS
  Under normal bone-implant interface conditions, the two diverging lateral KW configuration offers satisfactory mechanical stability and may be the preferred choice of SCHF fixation. When KW-bone bonding is suboptimal, as when one or more of the lateral KWs are re-drilled, addition of a medial KW should be considered in order to improve stability despite risk to ulnar nerve.
authors.affiliation: Pediatric Orthopedics, Hadassah University Hospital, P.O.B. 12000, Jerusalem, Israel.
authors.forename: Ron
authors.initials: R
authors.lastname: Lamdan
authors.affiliation: Department of Orthopaedic Surgery, Hadassah University Hospital, P.O.B. 12000, Jerusalem, Israel.
authors.forename: Meir
authors.initials: M
authors.lastname: Liebergall
authors.affiliation: The Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, 69978 Ramat Aviv, Israel.
authors.forename: Amit
authors.initials: A
authors.lastname: Gefen
authors.affiliation: Department of Orthopaedic Surgery, Hadassah University Hospital, P.O.B. 12000, Jerusalem, Israel.
authors.forename: Naum
authors.initials: N
authors.lastname: Symanovsky
authors.affiliation: Department of Biomedical Engineering, Hadassah University Medical Centre, P.O.B. 12000, Jerusalem, Israel.
authors.forename: Eran
authors.initials: E
authors.lastname: Peleg
keywords: Finite elements; Kirschner wires; Pediatric; Supra-condylar