title: Morphologic analysis of periprosthetic fractures after hip resurfacing arthroplasty.
abstract: BACKGROUND
  Periprosthetic fractures have long been recognized as one of the major complications of hip resurfacing arthroplasty. The objective of this study was to develop a systematic and morphologic classification of the fracture mode based on pathogenesis.
  
  
  METHODS
  One hundred and seven retrieved specimens consisting of the femoral remnant and the femoral component of a total hip resurfacing arthroplasty that had failed as a result of a periprosthetic fracture were analyzed with regard to the morphologic failure mode. The location of the fracture line was used to differentiate the fractures. The fractures were also classified histopathologically as acute biomechanical, acute postnecrotic, or chronic biomechanical.
  
  
  RESULTS
  Fifty-nine percent (sixty-three) of the fractures occurred within the bone inside the femoral component. Fifty-one percent (fifty-five) of the fractures were classified morphologically as acute postnecrotic; 40% (forty-three), as chronic biomechanical; and 8% (nine), as acute biomechanical. Acute biomechanical fractures were found exclusively in the femoral neck and occurred earlier (mean time [and standard deviation] between implantation and revision, 41 +/- 57 days) than acute postnecrotic fractures (mean time between implantation and revision, 149 +/- 168 days; p = 0.002) or chronic biomechanical fractures (mean time between implantation and revision, 179 +/- 165 days; p = 0.001). The latter two fracture types both occurred predominantly in the bone inside the femoral component.
  
  
  CONCLUSIONS
  Three distinct fracture modes were characterized morphologically. Osteonecrosis was the most frequent cause of fracture-related failures. We suggest that an intraoperative mechanical injury of the femoral neck such as notching and/or malpositioning of the femoral component might lead to changes in the loading pattern or in the resistance to fracture of the femoral neck and may result in both acute and chronic biomechanical femoral neck fractures. These findings may serve as feedback information for the surgeon and possibly influence future therapeutic strategies.
authors.affiliation: Departments of Pathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. j.zustin@uke.uni-hamburg.de
authors.forename: Jozef
authors.initials: J
authors.lastname: Zustin
authors.forename: Matthias
authors.initials: M
authors.lastname: Krause
authors.forename: Stefan
authors.initials: S
authors.lastname: Breer
authors.forename: Michael
authors.initials: M
authors.lastname: Hahn
authors.forename: Christoph
authors.initials: C
authors.lastname: von Domarus
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Rüther
authors.forename: Guido
authors.initials: G
authors.lastname: Sauter
authors.forename: Michael M
authors.initials: MM
authors.lastname: Morlock
authors.forename: Michael
authors.initials: M
authors.lastname: Amling
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D001696:Biomechanical Phenomena; D019544:Equipment Failure Analysis; D005260:Female; D005264:Femoral Fractures / Q000473:pathology*; D006621:Hip Joint / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D015207:Osteoarthritis, Hip / Q000601:surgery; D057068:Periprosthetic Fractures / Q000473:pathology*; D012086:Reoperation