title: Comparing conventional and computer-assisted surgery baseplate and screw placement in reverse shoulder arthroplasty.
abstract: BACKGROUND
  Preoperative planning and intraoperative navigation technologies have each been shown separately to be beneficial for optimizing screw and baseplate positioning in reverse shoulder arthroplasty (RSA) but to date have not been combined. This study describes development of a system for performing computer-assisted RSA glenoid baseplate and screw placement, including preoperative planning, intraoperative navigation, and postoperative evaluation, and compares this system with a conventional approach.
  
  
  METHODS
  We used a custom-designed system allowing computed tomography (CT)-based preoperative planning, intraoperative navigation, and postoperative evaluation. Five orthopedic surgeons defined common preoperative plans on 3-dimensional CT reconstructed cadaveric shoulders. Each surgeon performed 3 computer-assisted and 3 conventional simulated procedures. The 3-dimensional CT reconstructed postoperative units were digitally matched to the preoperative model for evaluation of entry points, end points, and angulations of screws and baseplate. Values were used to find accuracy and precision of the 2 groups with respect to the defined placement. Statistical analysis was performed by t tests (α = .05).
  
  
  RESULTS
  Comparison of the groups revealed no difference in accuracy or precision of screws or baseplate entry points (P > .05). Accuracy and precision were improved with use of navigation for end points and angulations of 3 screws (P < .05). Accuracy of the inferior screw showed a trend of improvement with navigation (P > .05). Navigated baseplate end point precision was improved (P < .05), with a trend toward improved accuracy (P > .05).
  
  
  CONCLUSIONS
  We conclude that CT-based preoperative planning and intraoperative navigation allow improved accuracy and precision for screw placement and precision for baseplate positioning with respect to a predefined placement compared with conventional techniques in RSA.
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada. Electronic address: 0gv@queensu.ca.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Venne
authors.affiliation: Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Rasquinha
authors.affiliation: Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada; Department of Surgery, Queen's University, Kingston, ON, Canada; Kingston General Hospital, Kingston, ON, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Pichora
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada; Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada; Department of Surgery, Queen's University, Kingston, ON, Canada; Kingston General Hospital, Kingston, ON, Canada; School of Computing, Queen's University, Kingston, ON, Canada.
authors.forename: Randy E
authors.initials: RE
authors.lastname: Ellis
authors.affiliation: Department of Surgery, Queen's University, Kingston, ON, Canada; Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Ryan
authors.initials: R
authors.lastname: Bicknell
mesh_terms: D019643:Arthroplasty, Replacement / Q000379:methods*; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D006801:Humans; D021621:Imaging, Three-Dimensional; D012540:Scapula / Q000601:surgery; D012785:Shoulder Joint / Q000601:surgery*; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: Computer-assisted surgery; reverse shoulder arthroplasty