title: A pre-operative approach of range of motion simulation and verification for femoroacetabular impingement.
abstract: BACKGROUND
  Femoroacetabular impingement (FAI) is increasingly recognized as a potential cause of hip osteoarthritis. A system capable of pre-operatively simulating hip range of motion (ROM) by given surface models from either healthy or FAI diseased bone is desirable.
  
  
  METHODS
  An impingement detection system using bounding sphere hierarchies was first developed. Both precision and accuracy of the impingement detection system were verified by a custom-designed phantom to imitate ball-and-socket hip movement. The impingement detection system was then implemented into the hip ROM simulation system to simulate the ROM of (1) healthy pelvis and femur, and (2) healthy pelvis and pathologic femur. The ROM simulation system was also verified by manipulating sawbones under the navigation of an optical tracking system.
  
  
  RESULTS
  The impingement detection system achieved a distance error of 0.53 ± 0.06 mm and an angular error of 0.28 ± 0.03°. The impingement detection accuracies were 100%, 100%, and 96% in three different phantom orientations, respectively. The mean errors between simulated and verified ROM were 0.10 ± 1.39° for the 'healthy pelvis and femur' group, and - 2.38 ± 3.49° for the 'healthy pelvis and pathologic femur' group.
  
  
  CONCLUSIONS
  The present study demonstrates a pre-operative approach to virtually simulate and predict the functional hip ROM based on the given bone models. The impingement detection and ROM simulation systems developed may also be used for other orthopedic applications.
authors.affiliation: Department of Biomedical Engineering, University of Miami, 1251 Memorial Drive, Coral Gables, FL, 33146 USA; MAKO Surgical Corp., 2555 Davie Road, Ft. Lauderdale, FL, 33317 USA.
authors.forename: Ta-Cheng
authors.initials: TC
authors.lastname: Chang
authors.forename: Hyosig
authors.initials: H
authors.lastname: Kang
authors.forename: Louis
authors.initials: L
authors.lastname: Arata
authors.forename: Weizhao
authors.initials: W
authors.lastname: Zhao
mesh_terms: D000077:Acetabulum / Q000473:pathology; D000465:Algorithms; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D057925:Femoracetabular Impingement / Q000601:surgery*; D005269:Femur / Q000473:pathology / Q000601:surgery; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D009985:Orthopedics / Q000379:methods; D010388:Pelvis / Q000601:surgery; D019047:Phantoms, Imaging; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D012371:Robotics; D012399:Rotation; D012984:Software