title: Three-dimensional planning and use of patient-specific guides improve glenoid component position: an in vitro study.
abstract: BACKGROUND
  Glenoid component positioning is a key factor for success in total shoulder arthroplasty. Three-dimensional (3D) measurements of glenoid retroversion, inclination, and humeral head subluxation are helpful tools for preoperative planning. The purpose of this study was to assess the reliability and precision of a novel surgical method for placing the glenoid component with use of patient-specific templates created by preoperative surgical planning and 3D modeling.
  
  
  METHODS
  A preoperative computed tomography examination of cadaveric scapulae (N = 18) was performed. The glenoid implants were virtually placed, and patient-specific guides were created to direct the guide pin into the desired orientation and position in the glenoid. The 3D orientation and position of the guide pin were evaluated by performing a postoperative computed tomography scan for each scapula. The differences between the preoperative planning and the achieved result were analyzed.
  
  
  RESULTS
  The mean error in 3D orientation of the guide pin was 2.39°, the mean entry point position error was 1.05 mm, and the mean inclination angle error was 1.42°. The average error in the version angle was 1.64°. There were no technical difficulties or complications related to use of patient-specific guides for guide pin placement. Quantitative analysis of guide pin positioning demonstrated a good correlation between preoperative planning and the achieved position of the guide pin.
  
  
  CONCLUSIONS
  This study demonstrates the reliability and precision of preoperative planning software and patient-specific guides for glenoid component placement in total shoulder arthroplasty.
authors.affiliation: Centre Orthopédique Santy, Hôpital Privé Jean Mermoz, Lyon, France. Electronic address: walch.gilles@wanadoo.fr.
authors.forename: Gilles
authors.initials: G
authors.lastname: Walch
authors.affiliation: Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Vezeridis
authors.affiliation: Hôpital de L'Archet 2, Nice, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Boileau
authors.affiliation: Tornier, Grenoble, France.
authors.forename: Pierric
authors.initials: P
authors.lastname: Deransart
authors.affiliation: Telecom Bretagne, Brest, France; Imascap, Brest, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Chaoui
mesh_terms: D000368:Aged; D019643:Arthroplasty, Replacement / Q000379:methods*; D002102:Cadaver; D003198:Computer Simulation; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D066298:In Vitro Techniques; D008297:Male; D010347:Patient Care Planning; D015203:Reproducibility of Results; D012540:Scapula / Q000000981:diagnostic imaging / Q000601:surgery; D012785:Shoulder Joint / Q000601:surgery*; D012984:Software; D014057:Tomography, X-Ray Computed
keywords: 3D; Total shoulder arthroplasty; computed tomography; glenoid component position; patient-specific guides; preoperative planning