title: A complete-pelvis segmentation framework for image-free total hip arthroplasty (THA): methodology and clinical study.
abstract: BACKGROUND
  Complete-pelvis segmentation in antero-posterior pelvic radiographs is required to create a patient-specific three-dimensional pelvis model for surgical planning and postoperative assessment in image-free navigation of total hip arthroplasty.
  
  
  METHODS
  A fast and robust framework for accurately segmenting the complete pelvis is presented, consisting of two consecutive modules. In the first module, a three-stage method was developed to delineate the left hemi-pelvis based on statistical appearance and shape models. To handle complex pelvic structures, anatomy-specific information processing techniques were employed. As the input to the second module, the delineated left hemi-pelvis was then reflected about an estimated symmetry line of the radiograph to initialize the right hemi-pelvis segmentation. The right hemi-pelvis was segmented by the same three-stage method,
  
  
  RESULTS
  Two experiments conducted on respectively 143 and 40 AP radiographs demonstrated a mean segmentation accuracy of 1.61±0.68 mm. A clinical study to investigate the postoperative assessment of acetabular cup orientations based on the proposed framework revealed an average accuracy of 1.2°±0.9° and 1.6°±1.4° for anteversion and inclination, respectively. Delineation of each radiograph costs less than one minute.
  
  
  CONCLUSIONS
  Despite further validation needed, the preliminary results implied the underlying clinical applicability of the proposed framework for image-free THA.
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, CH-3014, Bern, Switzerland.|Graduate School for Cellular and Biomedical Sciences, University of Bern, Switzerland.|BG Trauma Centre Ludwigshafen at Heidelberg University Hospital, Ludwigshafen, Germany.
authors.forename: Weiguo
authors.initials: W
authors.lastname: Xie
authors.affiliation: BG Trauma Centre Ludwigshafen at Heidelberg University Hospital, Ludwigshafen, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Franke
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, CH-3014, Bern, Switzerland.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.affiliation: BG Trauma Centre Ludwigshafen at Heidelberg University Hospital, Ludwigshafen, Germany.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Grützner
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, CH-3014, Bern, Switzerland.
authors.forename: Steffen
authors.initials: S
authors.lastname: Schumann
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, CH-3014, Bern, Switzerland.
authors.forename: Lutz-P
authors.initials: LP
authors.lastname: Nolte
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, CH-3014, Bern, Switzerland.
authors.forename: Guoyan
authors.initials: G
authors.lastname: Zheng
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000601:surgery; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D010388:Pelvis / Q000000981:diagnostic imaging / Q000601:surgery; D011859:Radiography; D025321:Surgery, Computer-Assisted / Q000379:methods*
keywords: acetabular cup orientation; computer-assisted orthopaedic surgery; image-free total hip arthroplasty; radiograph segmentation; statistical model