title: Effects of hip joint center location and femoral offset on abductor muscle strength after total hip arthroplasty.
abstract: OBJECTIVE
  The purposes of this study were 1) to examine the changes in the hip joint center (HJC) position and the femoral offset (FO) after total hip arthroplasty (THA) and 2) to investigate the effects of the HJC and FO on isometric abductor muscle strength.
  
  
  METHODS
  We evaluated 51 patients who underwent unilateral primary THA. The FO, and horizontal and vertical distances from the HJC to the tip of the teardrop were measured and isometric hip abductor muscle strength was measured.
  
  
  RESULTS
  The HJC of the affected side moved medially postoperatively compared with that of the unaffected side (p < 0.05), and the FO was reconstructed similarly to the unaffected side. There were significant negative correlations between the changes in the horizontal distance from the HJC and FO to the tip of the teardrop. An increase in the FO and infero-medial cup position optimized hip abductor muscle strength.
  
  
  CONCLUSIONS
  The HJC was reconstructed medially and superiorly, and the change in the FO after THA was influenced by the change in the horizontal distance of the HJC. Multiple regression analysis revealed that the medial and inferior HJC and increase in the FO constitute an effective procedure for restoring abductor strength.
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University , Yokohama , Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Tezuka
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Inaba
authors.forename: Naomi
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ike
authors.forename: So
authors.initials: S
authors.lastname: Kubota
authors.forename: Masaki
authors.initials: M
authors.lastname: Kawamura
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Saito
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D005269:Femur; D005271:Femur Head Necrosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D011184:Postoperative Period; D011859:Radiography; D012189:Retrospective Studies
keywords: Femoral offset; Hip abductor strength; Hip joint center; Total hip arthroplasty