title: Optimal glenoid component inclination in reverse shoulder arthroplasty. How to improve implant stability.
abstract: OBJECTIVE
  The purpose of this study is to demonstrate that inferior inclination of the glenosphere is a protecting factor from joint dislocation in reverse total shoulder replacement. The hypothesis is that an average of 10° of inferior inclination of the glenoid component would determine a significant inferior rate of dislocation as compared to neutral inclination.
  
  
  METHODS
  A retrospective case (dislocation)-control (stability of the implant) study was performed. Inclusion criteria were the homogeneity of the prosthetic model and availability of pre- and postoperative imaging of the shoulder, including antero-posterior and axillary X-ray views. Glenoid and glenosphere inclination were calculated according to standardized methods. Difference in between the angles determined the inferior tilt.
  
  
  RESULTS
  Thirty-three cases fit the inclusion criteria. Glenoid and glenosphere inclination measured, respectively, 74.1° and 83.5°. The average tilt of the glenosphere measured 9.4°. The average tilt in stable patients was 10.2°. Tilt in patients with atraumatic dislocation measured, respectively, -6.9° (superior tilt) and 2.4°, while it was 8.3° for the patient with traumatic instability. The association between the tilt of glenosphere and atraumatic dislocation was significant.
  
  
  CONCLUSIONS
  A 10° inferior tilt of the glenoid component in reverse shoulder arthroplasty is associated with a reduced risk of dislocation when compared to neutral tilt.
authors.affiliation: Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Milan, Italy. pietro.randelli@unimi.it.|IRCCS Policlinico San Donato, Via Morandi 30, 20097, San Donato Milanese, Milan, Italy. pietro.randelli@unimi.it.
authors.forename: P
authors.initials: P
authors.lastname: Randelli
authors.affiliation: IRCCS Policlinico San Donato, Via Morandi 30, 20097, San Donato Milanese, Milan, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Randelli
authors.affiliation: IRCCS Policlinico San Donato, Via Morandi 30, 20097, San Donato Milanese, Milan, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Arrigoni
authors.affiliation: IRCCS Policlinico San Donato, Via Morandi 30, 20097, San Donato Milanese, Milan, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Ragone
authors.affiliation: IRCCS Policlinico San Donato, Via Morandi 30, 20097, San Donato Milanese, Milan, Italy.
authors.forename: R
authors.initials: R
authors.lastname: D'Ambrosi
authors.affiliation: IRCCS Policlinico San Donato, Via Morandi 30, 20097, San Donato Milanese, Milan, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Masuzzo
authors.affiliation: Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Milan, Italy.|IRCCS Policlinico San Donato, Via Morandi 30, 20097, San Donato Milanese, Milan, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Cabitza
authors.affiliation: Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Milan, Italy.|IRCCS Istituto Ortopedico Galeazzi, Milan, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Banfi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019643:Arthroplasty, Replacement / Q000379:methods; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007593:Joint Instability; D007595:Joint Prosthesis; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome
keywords: Glenosphere inferior tilt; Instability; Reverse shoulder arthroplasty