title: Does component alignment affect gait symmetry in unilateral total hip arthroplasty patients?
abstract: BACKGROUND
  Component malposition in total hip arthroplasty patients has been associated with adverse clinical outcomes. However, whether the component alignment influences hip dynamic performance following total hip arthroplasty remains unclear. The purpose of this study was to investigate the relationship between the component alignment and in vivo hip kinematics during gait.
  
  
  METHODS
  Nineteen unilateral total hip arthroplasty patients received CT scan for creation of 3D hip models. The component alignment between the non-implanted and implanted hips were measured and compared. Three-dimensional hip kinematics for both hips of the total hip arthroplasty patients during gait was quantified using a dual fluoroscopic imaging technique. The differences between the implanted and non-implanted hip kinematics during gait were calculated. A forward stepwise multiple linear regression was performed to evaluate the relationships between the changes in implanted hip kinematics and the differences in component alignment with respect to the non-implanted hips.
  
  
  RESULTS
  An average 5.1° (SD 6.5°; range -11.1° to 18.3°) increase in internal rotation was observed in the implanted hip than the contralateral non-implanted hip and significantly correlated with a linear combination of the increase of cup anteversion, cup medial translation and leg lengthening (R=0.81).
  
  
  CONCLUSIONS
  Results suggested that the total hip arthroplasty patients compensated the changes in hip geometry by altering the dynamic movement during gait. Restoration of the native hip geometry, including acetabular cup anteversion, position and leg length could be one of the factors that influence the hip kinematics symmetry in total hip arthroplasty patients during gait.
authors.affiliation: Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Tsung-Yuan
authors.initials: TY
authors.lastname: Tsai
authors.affiliation: Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Jing-Sheng
authors.initials: JS
authors.lastname: Li
authors.affiliation: Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Dimitriou
authors.affiliation: Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA. Electronic address: ymkwon@mgh.harvard.edu.
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Kwon
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000503:physiopathology*; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D005471:Fluoroscopy; D005684:Gait; D006615:Hip / Q000000981:diagnostic imaging / Q000601:surgery; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D014057:Tomography, X-Ray Computed
keywords: Component alignment; Fluoroscope; Gait; Kinematics; Total hip arthroplasty