title: Effect of scapular pillar anatomy on scapular impingement in adduction and rotation after reverse shoulder arthroplasty.
abstract: BACKGROUND
  Notching of the scapular pillar is the main radiographic complication seen during follow-up of reverse shoulder arthroplasties. Several recommendations pertaining to the implantation technique and glenoid component design have been suggested. No studies have investigated potential anatomic risk factors for inferior scapular impingement.
  
  
  OBJECTIVE
  A specific anatomic shape of the scapular pillar promotes the development of notching.
  
  
  METHODS
  The Aequalis Reversed(®) (Tornier Inc., Edina, MN, USA) prosthesis was implanted into 40 cadaver scapulae. We measured maximal range-of-motion (ROM) in internal rotation, external rotation, and adduction. The anatomic specimens were then imaged using two-dimensional computed tomography (CT) and the scapular neck angle, surface area under the scapular pillar, and distance from the central glenosphere peg to the inferior glenoid rim were measured. Associations between these CT parameters and ROM values were assessed using statistical independence tests.
  
  
  RESULTS
  ROM values were greatest when the surface area under the scapular pillar was above 0.8 cm(2) (P<0.5). This feature combined with a scapular neck angle less than 105° produced the largest ROM values (P<0.5).
  
  
  CONCLUSIONS
  The scapular neck angle alone is not sufficient to identify a scapular morphology that increases the risk of notching. The surface area under the scapular pillar, in contrast, discriminates between scapulae with and without a high risk of notching. The surface area under the scapular pillar is influenced by the inferior glenoid offset.
  
  
  CONCLUSIONS
  We were unable to define a specific scapular shape at high risk for notching. The prevention of notching should rely chiefly on a rigorous glenoid component implantation technique, with particular attention to the inferior offset.
  
  
  METHODS
  III, experimental study.
authors.affiliation: Service d'orthopédie traumatologie 2A, CHRU Trousseau, faculté de médecine de Tours, université François-Rabelais de Tours, 1C, avenue de la République, 37170 Chambray-les-Tours, France; Laboratoire d'informatique, école d'ingénieurs polytechnique universitaire de Tours, université François-Rabelais de Tours, 64, avenue Portalis, 37200 Tours, France. Electronic address: julien.berhouet@gmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Berhouet
authors.affiliation: Service d'orthopédie traumatologie 2A, CHRU Trousseau, faculté de médecine de Tours, université François-Rabelais de Tours, 1C, avenue de la République, 37170 Chambray-les-Tours, France.
authors.forename: P
authors.initials: P
authors.lastname: Garaud
authors.affiliation: Laboratoire d'informatique, école d'ingénieurs polytechnique universitaire de Tours, université François-Rabelais de Tours, 64, avenue Portalis, 37200 Tours, France.
authors.forename: M
authors.initials: M
authors.lastname: Slimane
authors.affiliation: Laboratoire d'informatique, école d'ingénieurs polytechnique universitaire de Tours, université François-Rabelais de Tours, 64, avenue Portalis, 37200 Tours, France.
authors.forename: J
authors.initials: J
authors.lastname: Nicot
authors.affiliation: Laboratoire d'informatique, école d'ingénieurs polytechnique universitaire de Tours, université François-Rabelais de Tours, 64, avenue Portalis, 37200 Tours, France.
authors.forename: J
authors.initials: J
authors.lastname: Banah
authors.affiliation: Service de radiologie, clinique Saint-Gatien, 8, place de la Cathédrale, 37000 Tours, France.
authors.forename: E
authors.initials: E
authors.lastname: Waynberger
authors.affiliation: Service d'orthopédie traumatologie 2A, CHRU Trousseau, faculté de médecine de Tours, université François-Rabelais de Tours, 1C, avenue de la République, 37170 Chambray-les-Tours, France.
authors.forename: L
authors.initials: L
authors.lastname: Favard
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019643:Arthroplasty, Replacement / Q000379:methods*; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D012540:Scapula / Q000000981:diagnostic imaging*; D019534:Shoulder Impingement Syndrome / Q000517:prevention & control*; D012785:Shoulder Joint / Q000601:surgery*; D014057:Tomography, X-Ray Computed
keywords: Glenosphere offset; Notching; Scapular pillar; Shoulder; Total reverse shoulder arthroplasty