title: Reverse shoulder glenoid baseplate fixation: a comparison of flat-back versus curved-back designs and oval versus circular designs with 2 different offset glenospheres.
abstract: BACKGROUND
  In this glenoid loosening study, we compared the fixation strength of multiple generic reverse shoulder glenoid baseplates that differed only in backside geometry and shape and size to optimize design from a fixation perspective.
  
  
  METHODS
  The fixation strength of 4 generic baseplates was quantified in a low-density polyurethane substrate to isolate the contribution of baseplate profile and size (25 mm circular vs 25 × 34 mm oval) and backside geometry (flat back vs curved back) on fixation using 2 center-of-rotation glenospheres (0 mm and 10 mm lateral). The cyclic test simulated 55° of abduction as a 750 N load was continuously applied to induce a variable shear and compressive load. Before and after cyclic loading, baseplate displacement was measured in the directions of the applied static shear and compressive loads. Each generic baseplate was cyclically tested 7 times with each offset glenosphere for a total of 56 samples.
  
  
  RESULTS
  Circular baseplates were associated with significantly more shear displacement in both the superior-inferior (SI) and anterior-posterior (AP) directions after cyclic loading than oval baseplates. No such significant differences in fixation were observed between flat-back and curved-back baseplates. Circular baseplates were also associated with significantly more SI and AP shear displacement with 10 mm glenospheres than with 0 mm glenospheres. No significant difference in SI or AP motion was observed with oval baseplates between 0 mm and 10 mm glenospheres.
  
  
  CONCLUSIONS
  Our results suggest that baseplate shape and size affects fixation strength more than backside geometry. The 25 × 34 mm oval baseplates showed better fixation characteristics than their 25 mm circular counterparts; no discernible difference in fixation was observed between flat-back and curved-back baseplates.
authors.affiliation: Exactech, Gainesville, FL, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Roche
authors.affiliation: Exactech, Gainesville, FL, USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Stroud
authors.affiliation: Bordeaux-Merignac Clinic, Bordeaux-Merignac, France.
authors.forename: Pierre-Henri
authors.initials: PH
authors.lastname: Flurin
authors.affiliation: Department of Orthopedics, University of Florida, Gainesville, FL, USA.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Wright
authors.affiliation: Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, NY, USA. Electronic address: joseph.zuckerman@nyumc.org.
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Zuckerman
authors.affiliation: Department of Orthopaedic Surgery, Wright State University, Dayton, OH, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: DiPaola
mesh_terms: D019643:Arthroplasty, Replacement / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D001860:Bone Plates; D019544:Equipment Failure Analysis; D007595:Joint Prosthesis; D008953:Models, Anatomic; D011474:Prosthesis Design; D012540:Scapula / Q000601:surgery; D012785:Shoulder Joint / Q000601:surgery
keywords: Reverse shoulder arthroplasty; glenoid fixation