title: [Periprosthetic and interimplant femoral fractures: Biomechanical analysis].
abstract: BACKGROUND
  The requirements for treatment of femoral fractures are increasing with the rising age of the patients. The aim of this study was to evaluate femoral stiffness and the fracture risk after inserting different implants and implant combinations.
  
  
  METHODS
  A total of 48 cadaveric femors were harvested and 8 groups were randomized on the basis of the bone mineral density (BMD). Different osteosyntheses following prosthetic stem implantation (hip and knee prostheses) were performed and compared with native femurs. All specimens were biomechanically tested in a four-point bending until fracture.
  
  
  RESULTS
  The insertion of a femoral stem decreases the stiffness by approximately 33%. Ipsilateral retrograde nailing reduces the force to failure even more. This instable situation can be stabilized by a lateral locking compression plate. The most stable situation occurred in the presence of two cemented stems.
  
  
  CONCLUSIONS
  Taken together these results clearly indicate that a hip prosthesis significantly weakens the femur, whereas two stems produce the most stable situation at all. The situation of a hip prosthesis and an retrograde nail should be avoided or covered by a bridging-osteosynthesis. In clinical practice an extramedullary fixation technique for distal femoral fractures should be preferred.
authors.affiliation: Klinik und Poliklinik für Unfall-, Hand- und Wiederherstellungschirurgie, Universitätsklinik Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Deutschland.|Abteilung für Kinderorthopädie, Altonaer-Kinderkrankenhaus Hamburg, Hamburg, Deutschland.
authors.forename: M
authors.initials: M
authors.lastname: Rupprecht
authors.affiliation: Klinik und Poliklinik für Unfall-, Hand- und Wiederherstellungschirurgie, Universitätsklinik Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Deutschland.
authors.forename: C
authors.initials: C
authors.lastname: Schlickewei
authors.affiliation: Klinik und Poliklinik für Unfall-, Hand- und Wiederherstellungschirurgie, Universitätsklinik Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Deutschland.
authors.forename: F
authors.initials: F
authors.lastname: Fensky
authors.affiliation: Institut für Biomechanik, Technische Universität Hamburg-Harburg, Hamburg-Harburg, Deutschland.
authors.forename: M
authors.initials: M
authors.lastname: Morlock
authors.affiliation: Instituts für Rechtsmedizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg-Eppendorf, Deutschland.
authors.forename: K
authors.initials: K
authors.lastname: Püschel
authors.affiliation: Klinik und Poliklinik für Unfall-, Hand- und Wiederherstellungschirurgie, Universitätsklinik Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Deutschland.
authors.forename: J M
authors.initials: JM
authors.lastname: Rueger
authors.affiliation: Klinik und Poliklinik für Unfall-, Hand- und Wiederherstellungschirurgie, Universitätsklinik Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Deutschland. w.lehmann@uke.de.
authors.forename: W
authors.initials: W
authors.lastname: Lehmann
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation* / Q000379:methods; D019245:Compressive Strength; D055119:Elastic Modulus; D005260:Female; D005264:Femoral Fractures / Q000503:physiopathology* / Q000628:therapy*; D005269:Femur / Q000503:physiopathology*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D013314:Stress, Mechanical; D013718:Tensile Strength; D016896:Treatment Outcome
keywords: Bridging osteosynthesis; Fracture, femoral; Fracture, interprosthetic; Load stability; Osteoporosis