title: Plate fixation in periprosthetic femur fractures Vancouver type B1-Trochanteric hook plate or subtrochanterical bicortical locking?
abstract: BACKGROUND
  Proximal plate fixation in periprosthetic femur fractures can be improved by plate anchorage in the greater trochanter (lateral tension band principle) or bicortical locking screw placement beside the prosthesis stem in an embracement configuration. Both concepts were compared in a biomechanical test using a femoral hook plate (hook) or a locking attachment plate (LAP).
  
  
  METHODS
  After bone mineral density (BMD) measurement in the greater trochanter, six pairs of fresh frozen human femora were assigned to two groups and instrumented with cemented hip endoprostheses. A transverse osteotomy was set distal to the tip of the prosthesis, simulating a Vancouver B1 fracture. Each pair was instrumented using a plate tensioner with either hook or LAP construct. Cyclic testing (2Hz) with physiologic profile and monotonically increasing load was performed until catastrophic failure. Plate stiffness was compared in a four-point-bending-test. Paired student's-t-test was used for statistical evaluation (p<0.05).
  
  
  RESULTS
  Mean BMD was 250mgHA/ccm±47. The hook construct exhibited a significantly (p=0.015) lower number of cycles and load to failure (26'177cycles±2777; 3'118N±778) correlating significantly with BMD (R2=0.83; p=0.04) compared to the LAP construct (37'423cycles±5'299; 4'242N±1'030) (R2=0.71;p=0.11). BMD was a significant covariate (p=0.01). Plate stiffness was in a comparable range (hook Plate 468N/mm±7; LCP 445N/mm±6).
  
  
  CONCLUSIONS
  Subtrochanterically placed LAP provides an increased fixation strength under repetitive loading compared to hook plate fixation in the greater trochanter. Trochanteric fixation is highly BMD dependent and may be restricted to major greater trochanteric involvement requiring stabilization.
authors.affiliation: AO Research Institute Davos, Clavadelerstrasse 8, CH-7270, Davos-Platz, Switzerland; Department of Trauma, Hand and Reconstructive Surgery, University Hospital Jena, Am Klinikum 1, D-07747 Jena, Germany. Electronic address: lenzmar@web.de.
authors.forename: Mark
authors.initials: M
authors.lastname: Lenz
authors.affiliation: Cantonal Hospital Baselland, Rheinstrasse 26, CH-4410 Liestal, Switzerland; University of Basel, Basel, Switzerland. Electronic address: Karl.Stoffel@ksbl.ch.
authors.forename: Karl
authors.initials: K
authors.lastname: Stoffel
authors.affiliation: Department of Anatomy and Cell Biology, Martin-Luther-University Halle-Wittenberg, Faculty of Medicine, D-06097 Halle (Saale), Germany. Electronic address: heike.kielstein@medizin.uni-halle.de.
authors.forename: Heike
authors.initials: H
authors.lastname: Kielstein
authors.affiliation: Hansjörg Wyss Hip and Pelvis Center, University of Washington School of Medicine, 1959 Northeast Pacific Street B307, Seattle, WA 98195, USA. Electronic address: mayok@comcast.net.
authors.forename: Keith
authors.initials: K
authors.lastname: Mayo
authors.affiliation: Department of Trauma, Hand and Reconstructive Surgery, University Hospital Jena, Am Klinikum 1, D-07747 Jena, Germany. Electronic address: gunther.hofmann@med.uni-jena.de.
authors.forename: Gunther O
authors.initials: GO
authors.lastname: Hofmann
authors.affiliation: AO Research Institute Davos, Clavadelerstrasse 8, CH-7270, Davos-Platz, Switzerland. Electronic address: boyko.gueorguiev@aofoundation.org.
authors.forename: Boyko
authors.initials: B
authors.lastname: Gueorguiev
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D015519:Bone Density; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D005264:Femoral Fractures / Q000473:pathology / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D010027:Osteotomy; D057068:Periprosthetic Fractures / Q000473:pathology / Q000601:surgery*
keywords: Hook plate; Locking attachment plate; Periprosthetic femur fracture; Plate fixation; Vancouver B1