title: Testing of a novel pin array guide for accurate three-dimensional glenoid component positioning.
abstract: BACKGROUND
  A substantial challenge in total shoulder replacement is accurate positioning and alignment of the glenoid component. This challenge arises from limited intraoperative exposure and complex arthritic-driven deformity. We describe a novel pin array guide and method for patient-specific guiding of the glenoid central drill hole. We also experimentally tested the hypothesis that this method would reduce errors in version and inclination compared with 2 traditional methods.
  
  
  METHODS
  Polymer models of glenoids were created from computed tomography scans from 9 arthritic patients. Each 3-dimensional (3D) printed scapula was shrouded to simulate the operative situation. Three different methods for central drill alignment were tested, all with the target orientation of 5° retroversion and 0° inclination: no assistance, assistance by preoperative 3D imaging, and assistance by the pin array guide. Version and inclination errors of the drill line were compared.
  
  
  RESULTS
  Version errors using the pin array guide (3° ± 2°) were significantly lower than version errors associated with no assistance (9° ± 7°) and preoperative 3D imaging (8° ± 6°). Inclination errors were also significantly lower using the pin array guide compared with no assistance.
  
  
  CONCLUSIONS
  The new pin array guide substantially reduced errors in orientation of the central drill line. The guide method is patient specific but does not require rapid prototyping and instead uses adjustments to an array of pins based on automated software calculations. This method may ultimately provide a cost-effective solution enabling surgeons to obtain accurate orientation of the glenoid.
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine and M.S. Hershey Medical Center, Hershey, PA, USA.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Lewis
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine and M.S. Hershey Medical Center, Hershey, PA, USA.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Stevens
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine and M.S. Hershey Medical Center, Hershey, PA, USA. Electronic address: aarmstrong@hmc.psu.edu.
authors.forename: April D
authors.initials: AD
authors.lastname: Armstrong
mesh_terms: D019643:Arthroplasty, Replacement / Q000379:methods*; D001858:Bone Nails; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008954:Models, Biological; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000601:surgery*; D015203:Reproducibility of Results; D012540:Scapula / Q000601:surgery; D012785:Shoulder Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Glenoid positioning; alignment guide; preoperative planning; three-dimensional imaging; total shoulder arthroplasty