title: Risk of edge-loading and prosthesis impingement due to posterior pelvic tilting after total hip arthroplasty.
abstract: BACKGROUND
  Proper implant orientation is essential for avoiding edge-loading and prosthesis impingement in total hip arthroplasty. Although cup orientation is affected by a change in pelvic tilt after surgery, it has been unclear whether surgeons can prevent impingement and edge-loading by proper positioning by taking into account any change in pelvic alignment associated with alteration of hip range of motion.
  
  
  METHODS
  We simulated implant orientation without edge-loading and prosthesis impingement, even with a change in pelvic tilt and associated change in hip range of motion after surgery, by collision detection using implant models created with computer-aided design.
  
  
  RESULTS
  If posterior pelvic tilting with a corresponding hyperextension change in hip range of motion after surgery remains within 10°, as occurs in 90% of cases, surgeons can avoid edge-loading and impingement by correctly orienting the implant, even when using a conventional prosthesis. However, if a 20° change occurs after surgery, it may be difficult to avoid those risks.
  
  
  CONCLUSIONS
  Although edge-loading and impingement can be prevented by performing appropriate surgery in most cases, even when taking into account postoperative changes in pelvic tilt, it may also be important to pay attention to spinal conditions to ensure that pelvic tilting is not extreme because of increasing kyphosis.
authors.affiliation: Department of Orthopedic Surgery, Osaka National Hospital, Osaka, Japan. Electronic address: miki_osaka@nifty.com.
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Miki
authors.affiliation: Department of Orthopedic Surgery, Osaka National Hospital, Osaka, Japan. Electronic address: t_kyo@seichokai.or.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kyo
authors.affiliation: Department of Orthopedic Surgery, Osaka National Hospital, Osaka, Japan. Electronic address: cro_magnons5@yahoo.co.jp.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kuroda
authors.affiliation: Department of Orthopedic Surgery, Osaka National Hospital, Osaka, Japan. Electronic address: ichiro614@nifty.com.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Nakahara
authors.affiliation: Department of Orthopedic Surgery, Medical School of Osaka University, Osaka, Japan. Electronic address: n-sugano@umin.net.
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Sugano
mesh_terms: D000465:Algorithms; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods* / Q000592:standards; D017076:Computer-Aided Design; D019544:Equipment Failure Analysis / Q000379:methods; D006622:Hip Prosthesis; D006801:Humans; D010384:Pelvic Bones / Q000033:anatomy & histology / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011474:Prosthesis Design / Q000379:methods; D016059:Range of Motion, Articular
keywords: Cup orientation; Edge-loading; Pelvic tilt; Prosthesis impingement; Total hip arthroplasty