title: Finite element predictions of cartilage contact mechanics in hips with retroverted acetabula.
abstract: BACKGROUND
  A contributory factor to hip osteoarthritis (OA) is abnormal cartilage mechanics. Acetabular retroversion, a version deformity of the acetabulum, has been postulated to cause OA via decreased posterior contact area and increased posterior contact stress. Although cartilage mechanics cannot be measured directly in vivo to evaluate the causes of OA, they can be predicted using finite element (FE) modeling.
  
  
  OBJECTIVE
  The objective of this study was to compare cartilage contact mechanics between hips with normal and retroverted acetabula using subject-specific FE modeling.
  
  
  METHODS
  Twenty subjects were recruited and imaged: 10 with normal acetabula and 10 with retroverted acetabula. FE models were constructed using a validated protocol. Walking, stair ascent, stair descent and rising from a chair were simulated. Acetabular cartilage contact stress and contact area were compared between groups.
  
  
  RESULTS
  Retroverted acetabula had superomedial cartilage contact patterns, while normal acetabula had widely distributed cartilage contact patterns. In the posterolateral acetabulum, average contact stress and contact area during walking and stair descent were 2.6-7.6 times larger in normal than retroverted acetabula (P ≤ 0.017). Conversely, in the superomedial acetabulum, peak contact stress during walking was 1.2-1.6 times larger in retroverted than normal acetabula (P ≤ 0.044). Further differences varied by region and activity.
  
  
  CONCLUSIONS
  This study demonstrated superomedial contact patterns in retroverted acetabula vs widely distributed contact patterns in normal acetabula. Smaller posterolateral contact stress in retroverted acetabula than in normal acetabula suggests that increased posterior contact stress alone may not be the link between retroversion and OA.
authors.affiliation: Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, United States; Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT 84112, United States. Electronic address: corinne.henak@utah.edu.
authors.forename: C R
authors.initials: CR
authors.lastname: Henak
authors.forename: E D
authors.initials: ED
authors.lastname: Carruth
authors.forename: A E
authors.initials: AE
authors.lastname: Anderson
authors.forename: M D
authors.initials: MD
authors.lastname: Harris
authors.forename: B J
authors.initials: BJ
authors.lastname: Ellis
authors.forename: C L
authors.initials: CL
authors.lastname: Peters
authors.forename: J A
authors.initials: JA
authors.lastname: Weiss
mesh_terms: D000077:Acetabulum / Q000002:abnormalities* / Q000473:pathology / Q000503:physiopathology; D000328:Adult; D002358:Cartilage, Articular / Q000503:physiopathology*; D016022:Case-Control Studies; D005260:Female; D020342:Finite Element Analysis; D006621:Hip Joint / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008953:Models, Anatomic; D009043:Motor Activity / Q000502:physiology; D015207:Osteoarthritis, Hip / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D012307:Risk Factors; D013314:Stress, Mechanical; D016138:Walking / Q000502:physiology; D055815:Young Adult
keywords: Acetabular retroversion; Cartilage mechanics; Finite element; Hip; Osteoarthritis