title: Plate Positioning in Periprosthetic or Interprosthetic Femur Fractures With Stable Implants-A Biomechanical Study.
abstract: Angular stable plate fixation is a widely accepted treatment option for interprosthetic or periprosthetic femoral fractures with stable implants. This biomechanical study tries to establish a safe distance of the plate from the tip of a femoral prosthesis.
  
  
  
  A total of 38 composite femurs were reamed to an inner diameter of 23 mm to create an osteoporotic bone model. A Weber hip stem was cemented into each and a distal femoral NCB plate applied with the distance to the stem varying from 8 cm apart to 6 cm overlap in 2-cm steps. Each specimen was tested in cyclic axial loading (400 N-1500 N) and then cyclic torsion (0.6 Nm-50 Nm). Peak strain on the femur around the tip of the plate was measured with a 3D image correlation system and averaged over 26 cycles (excluding the first 3 and the last cycles). Finally, each femur was axially loaded to failure.
  
  
  
  Strain increased with decreasing overlap or gap. Seven specimens failed early between 2-cm overlap and 2-cm gap. Results were divided into a far group with a distance of >4 cm and a close group of <4 cm. Strain was significantly higher in the close group for axial (P < .001) and torsional (P < .001) loading. Failure load was significantly lower in the close group (P = .002).
  
  
  
  A minimal gap and/or overlap of at least 6 cm is recommended in osteoporotic bone to avoid stress risers.
authors.affiliation: Department of Orthopaedic Surgery, Orthopädische Klinik König-Ludwig-Haus, University of Würzburg, Würzburg, Germany.
authors.forename: Matthias G
authors.initials: MG
authors.lastname: Walcher
authors.affiliation: Department of Orthopaedic Surgery, Kantonsspital St. Gallen, St. Gallen, Switzerland.
authors.forename: Karlmeinrad
authors.initials: K
authors.lastname: Giesinger
authors.affiliation: University of Western Australia, Royal Perth Hospital, Perth, Western Australia, Australia.
authors.forename: Ryan
authors.initials: R
authors.lastname: du Sart
authors.affiliation: Department of Medical Engineering and Physics, Royal Perth Hospital, University of Western Australia, Perth, Western Australia, Australia.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Day
authors.affiliation: The University of Western Australia, Perth Orthopaedic Sports Medicine Centre, West Perth, Australia.
authors.forename: Markus S
authors.initials: MS
authors.lastname: Kuster
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D001842:Bone and Bones; D005264:Femoral Fractures / Q000601:surgery*; D005269:Femur / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D056888:Patient Positioning; D057068:Periprosthetic Fractures / Q000601:surgery*
keywords: biomechanics; cortical strain; locked plate; periprosthetic fractures; total hip arthroplasty