title: Bony increased-offset reversed shoulder arthroplasty: minimizing scapular impingement while maximizing glenoid fixation.
abstract: BACKGROUND
  Scapular notching, prosthetic instability, limited shoulder rotation and loss of shoulder contour are associated with conventional medialized design reverse shoulder arthroplasty. Prosthetic (ie, metallic) lateralization increases torque at the baseplate-glenoid interface potentially leading to failure.
  
  
  OBJECTIVE
  We asked whether bony lateralization of reverse shoulder arthroplasty would avoid the problems caused by humeral medialization without increasing torque or shear force applied to the glenoid component.
  
  
  METHODS
  We prospectively followed 42 patients with rotator cuff deficiency treated with bony increased-offset reverse shoulder arthroplasty. A cylinder of autologous cancellous bone graft, harvested from the humeral head, was placed between the reamed glenoid surface and baseplate. Graft and baseplate fixation was achieved using a lengthened central peg (25 mm) and four screws. Patients underwent clinical, radiographic, and CT assessment at a minimum of 2 years after surgery.
  
  
  RESULTS
  The humeral graft incorporated completely in 98% of cases (41 of 42) and partially in one. At a mean of 28 months postoperatively, no graft resorption, glenoid loosening, or postoperative instability was observed. Inferior scapular notching occurred in 19% (eight of 42). The absolute Constant-Murley score improved from 31 to 67. Thirty-six patients (86%) were able to internally rotate sufficiently to reach their back over the sacrum.
  
  
  CONCLUSIONS
  Grafting of the glenoid surface during reverse shoulder arthroplasty effectively creates a long-necked scapula, providing the benefits of lateralization. Bony increased-offset reverse shoulder arthroplasty is associated with low rates of inferior scapular notching, improved shoulder rotation, no prosthetic instability and improved shoulder contour. In contrast to metallic lateralization, bony lateralization has the advantage of maintaining the prosthetic center of rotation at the prosthesis-bone interface, thus minimizing torque on the glenoid component.
  
  
  METHODS
  Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery & Sports Traumatology, Hôpital de L'Archet-University of Nice-Sophia-Antipolis, 151 Route de St Antoine de Ginestière, 06202 Nice, France. boileau.p@chu-nice.fr
authors.forename: Pascal
authors.initials: P
authors.lastname: Boileau
authors.forename: Grégory
authors.initials: G
authors.lastname: Moineau
authors.forename: Yannick
authors.initials: Y
authors.lastname: Roussanne
authors.forename: Kieran
authors.initials: K
authors.lastname: O'Shea
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019643:Arthroplasty, Replacement / Q000009:adverse effects / Q000295:instrumentation; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D016025:Bone Transplantation / Q000009:adverse effects / Q000295:instrumentation; D005260:Female; D005602:France; D006801:Humans; D006811:Humerus / Q000637:transplantation*; D007595:Joint Prosthesis; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012540:Scapula / Q000293:injuries; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D013314:Stress, Mechanical; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D019415:Torque; D014182:Transplantation, Autologous; D016896:Treatment Outcome