title: Clinical evaluation of a biomechanical guidance system for periacetabular osteotomy.
abstract: BACKGROUND
  Populations suffering from developmental dysplasia of the hip typically have reduced femoral coverage and experience joint pain while walking. Periacetabular osteotomy (PAO) is one surgical solution that realigns the acetabular fragment. This challenging surgery has a steep learning curve. Existing navigation systems for computer-assisted PAO neither track the released fragment nor offer the means to assess fragment location. An intraoperative workstation--the biomechanical guidance system (BGS)--developed for PAO incorporates intraoperative fragment tracking and acetabular characterization through radiographic angles and joint biomechanics. In this paper, we investigate the accuracy and effectiveness of the BGS for bone fragment tracking and acetabular characterization in clinical settings as compared to conventional techniques and postoperative assessments. We also report the issues encountered and our remedies when using the BGS in the clinical setting.
  
  
  METHODS
  Eleven consecutive patients (aged 22-48, mean 34, years) underwent 12 PAO surgeries (one bilateral surgery) where the BGS collected information on acetabular positioning. These measurements were compared with postoperative CT data and manual measurements made intraoperatively.
  
  
  RESULTS
  No complications were reported during surgery, with surgical time-95-210 (mean 175) minutes-comparable to reported data for the conventional approach. The BGS-measured acetabular positioning showed strong agreement with postoperative CT measurements (-0.3-9.2, mean 3.7, degrees), whereas larger differences occurred between the surgeon's intraoperative manual measurements and postoperative CT measurements (-2.8-21.3, mean 10.5, degrees).
  
  
  CONCLUSIONS
  The BGS successfully tracked the acetabular fragment in a clinical environment without introducing complications to the surgical workflow. Accurate 3D positioning of the acetabulum may provide more information intraoperatively (e.g., anatomical angles and biomechanics) without adversely impacting the surgery to better understand potential patient outcomes.
authors.affiliation: Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD, 20723, USA. Ryan.Murphy@jhuapl.edu.
authors.forename: Ryan J
authors.identifier: http://orcid.org/0000-0003-3065-7700
authors.initials: RJ
authors.lastname: Murphy
authors.affiliation: Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD, 20723, USA.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Armiger
authors.affiliation: Orton Orthopaedic Hospital, Helsinki, Finland.
authors.forename: Jyri
authors.initials: J
authors.lastname: Lepistö
authors.affiliation: Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD, 20723, USA.|Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Mehran
authors.initials: M
authors.lastname: Armand
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000601:surgery*; D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D061646:Operative Time; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult
keywords: Biomechanics; Computer-assisted surgery; Dysplasia; Periacetabular osteotomy