title: Increased peak contact stress after incongruent reduction of transverse acetabular fractures: a cadaveric model.
abstract: BACKGROUND
  The objective of this study was to determine the peak contact pressure with varying degrees of articular cartilage step-off in a transtectal acetabular fracture model.
  
  
  METHODS
  Five fresh frozen cadaveric hip joints were potted in a custom loading fixture. The five specimens were then tested at loads of 445 N (newton) (100 lb) and 1,335 N (300 lb) intact and after a transverse osteotomy at step-off levels from 0 to 5 mm in 1-mm increments.
  
  
  RESULTS
  Articular cartilage step-off of greater than 1 mm led to significantly increased contact stress at the loaded acetabular articular surface. Mean peak pressure measured at 1,335 N of loading in all intact specimens before the osteotomy was approximately 10 MPa. Peak pressure after a transverse acetabular fracture did not change when the fracture was perfectly reduced. At 1 mm of step-off, the peak pressure increased by approximately 20% but was not statistically significant. With step-off of > 2 mm or greater, the peak pressure increase was approximately 50% and was statistically significant.
  
  
  CONCLUSIONS
  On the basis of our study, transverse acetabular fractures with greater than 1 mm of displacement can lead to significant increase in peak pressure at the articular surface.
authors.affiliation: Department of Orthopaedic Surgery, Orthopaedic Bioengineering Research Laboratory, University of Louisville, Louisville, Kentucky, USA. art.malkani@louisvill.edu
authors.forename: A L
authors.initials: AL
authors.lastname: Malkani
authors.forename: M J
authors.initials: MJ
authors.lastname: Voor
authors.forename: G
authors.initials: G
authors.lastname: Rennirt
authors.forename: D
authors.initials: D
authors.lastname: Helfet
authors.forename: D
authors.initials: D
authors.lastname: Pedersen
authors.forename: T
authors.initials: T
authors.lastname: Brown
mesh_terms: D000077:Acetabulum / Q000293:injuries*; D000368:Aged; D000704:Analysis of Variance; D002102:Cadaver; D002358:Cartilage, Articular / Q000502:physiology*; D050723:Fractures, Bone / Q000150:complications / Q000473:pathology*; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D015207:Osteoarthritis, Hip / Q000209:etiology / Q000517:prevention & control; D016474:Weight-Bearing