title: Preoperative and postoperative sagittal plane hip kinematics in patients with femoroacetabular impingement during level walking.
abstract: BACKGROUND
  Femoroacetabular impingement (FAI) has been linked to osteoarthritis. Treatment options range from nonoperative to operative, and current outcome measures are generally subjective or not conducted under actual activities of daily living. Thus, there is a need for the use of motion capture techniques to quantitatively assess the outcome of surgical intervention for those treated for FAI.
  
  
  OBJECTIVE
  The gait of FAI patients 1 year after operative treatment (arthroscopic hip reshaping) will be significantly closer to the normal range and pattern of hip flexion motion, relative to pretreatment.
  
  
  METHODS
  Case series; Level of evidence, 4.
  
  
  METHODS
  Eleven patients between 18 and 44 years of age with diagnosed FAI were enrolled in this study. Kinematics and kinetics for this group of patients were collected using motion capture techniques before arthroscopic bone-reshaping surgery and again 1 year after surgery. Pain and perceived activity level (Tegner scale) were also collected. All collected data were compared using a paired t test.
  
  
  RESULTS
  Overall hip sagittal plane range of motion increased on the affected side from 27.6° ± 5.0° to 30.7° ± 4.3° (P = .02). The presence of abnormal reversals (second-order change in the slope in the hip flexion/extension curve) that was present in 5 patients preoperatively disappeared or was reduced in prevalence and magnitude in 4 of the patients postoperatively. Additionally, pain decreased and activity level increased postoperatively.
  
  
  CONCLUSIONS
  The results supported the hypothesis that surgical intervention for FAI restores more normal patterns of gait and provides objective support that the surgical procedure is useful. The results help establish motion capture as a potential method for quantitatively assessing the outcome in FAI surgical interventions. The presence of abnormal reversals in hip flexion has been reported in end-stage hip osteoarthritis, and the presence of these reversals in FAI patients reinforces the idea of FAI being a precursor to hip osteoarthritis.
authors.affiliation: Mechanical Engineering, Stanford University, Stanford, CA 94305-4038, USA. rylandjh@stanford.edu
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Rylander
authors.forename: Beatrice
authors.initials: B
authors.lastname: Shu
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Andriacchi
authors.forename: Marc R
authors.initials: MR
authors.lastname: Safran
mesh_terms: D000293:Adolescent; D000328:Adult; D001182:Arthroscopy / Q000379:methods; D001696:Biomechanical Phenomena; D005260:Female; D057925:Femoracetabular Impingement / Q000503:physiopathology / Q000601:surgery*; D006615:Hip / Q000033:anatomy & histology* / Q000502:physiology; D006801:Humans; D008297:Male; D017063:Outcome Assessment, Health Care / Q000379:methods*; D016059:Range of Motion, Articular; D016138:Walking / Q000502:physiology*; D055815:Young Adult