title: Impact of inferior glenoid tilt, humeral retroversion, bone grafting, and design parameters on muscle length and deltoid wrapping in reverse shoulder arthroplasty.
abstract: OBJECTIVE
  This study quantifies the ability of humeral retroversion, glenoid tilt, bone graft, and varying prosthesis design parameters to restore anatomic muscle length and deltoid wrapping with reverse shoulder arthroplasty.
  
  
  METHODS
  A computer model simulated abduction and internal and external rotation for a normal shoulder, the RSP reverse shoulder, the Equinoxe reverse shoulder, and the Grammont reverse shoulder when implanted using various implantation methods. The length of eight different muscles and the deltoid wrapping angle were quantified to evaluate the ability of each implantation method and design to restore anatomic muscle tensioning.
  
  
  RESULTS
  Each reverse shoulder shifted the center of rotation medially and inferiorly relative to the normal shoulder and caused a corresponding shift in the position of the humerus. Each reverse shoulder elongated each head of the deltoid and shortened the internal and external rotators relative to the normal shoulder. The surgical techniques and prosthesis designs, which resulted in a more lateral humeral position, were associated with more deltoid wrapping and better tensioning of the anterior and posterior shoulder muscles.
  
  
  CONCLUSIONS
  Muscle tensioning and deltoid wrapping can be substantially altered by surgical implantation meth- ods using the Grammont reverse shoulder. However, the results of this study demonstrate that more anatomic muscle tensioning and improved deltoid wrapping are achieved using alternative prosthesis designs that better restore the lateral position of the humerus.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Roche
authors.forename: Phong
authors.initials: P
authors.lastname: Diep
authors.forename: Matthew
authors.initials: M
authors.lastname: Hamilton
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Crosby
authors.forename: Pierre-Henri
authors.initials: PH
authors.lastname: Flurin
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Wright
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Zuckerman
authors.forename: Howard D
authors.initials: HD
authors.lastname: Routman
mesh_terms: D019643:Arthroplasty, Replacement / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D016025:Bone Transplantation; D003198:Computer Simulation; D057645:Deltoid Muscle / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D006811:Humerus / Q000503:physiopathology / Q000601:surgery*; D007595:Joint Prosthesis; D008953:Models, Anatomic; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012785:Shoulder Joint / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome