title: Modular neck for prevention of prosthetic impingement in cases with excessively anteverted femur.
abstract: BACKGROUND
  It is important to adjust stem anteversion in cases of excessive femoral version to avoid prosthetic impingement-related complications in total hip arthroplasty. Although modular necks are considered an effective solution, their application in cases with wide variations in femoral anteversion remains to be elucidated. This study aimed to simulate the effects of different modular necks on prevention of prosthetic impingement due to excessive femoral anteversion.
  
  
  METHODS
  We investigated range of motion without prosthetic impingement by collision detection using implant computer-aided design models of the ANCA-Fit system.
  
  
  RESULTS
  Modular necks could provide an adequate range of motion in cases with up to 60° of femoral anteversion. However, few alternative necks were available in cases with excessive femoral anteversion, while many options could be used for femoral offset and version control in cases with average amounts of femoral anteversion without prosthetic impingement.
  
  
  CONCLUSIONS
  We conclude that modular necks might provide a marginal advantage over other options such as cemented, conical or modular stems for cases with an excessively anteverted femur, although they could help to maintain the femoral offset in some cases with average femoral anteversion.
authors.affiliation: Department of Orthopedic Surgery, Osaka National Hospital, Japan. miki_osaka@nifty.com
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Miki
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Sugano
mesh_terms: D000077:Acetabulum / Q000601:surgery; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D002516:Ceramics; D003198:Computer Simulation; D017076:Computer-Aided Design; D005269:Femur / Q000033:anatomy & histology*; D006621:Hip Joint / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D011474:Prosthesis Design / Q000379:methods*; D016059:Range of Motion, Articular; D012984:Software