title: Activities of daily living with reverse prostheses: importance of scapular compensation for functional mobility of the shoulder.
abstract: OBJECTIVE
  The nonanatomical design of reverse shoulder prostheses induce medial displacement of the center of rotation, impingements and may reduce the mobility of the shoulder. The aim of this study is to test the hypothesis that during activities of daily living functional mobility of the shoulder can be restored by scapular compensation.
  
  
  METHODS
  A numerical 3-dimensional model was developed to reproduce the movement of the scapula and humerus, during 4 activities of daily living measured experimentally. This hypothesis was tested in 4 configurations of the aequalis reverse prosthesis (standard 36-mm glenosphere, 42-mm glenosphere, lateralized 36-mm glenosphere, lateralized Bony Increased-Offset Reverse Shoulder Arthroplasty [BIO-RSA]), which were implanted in the virtual model. All impingement positions were evaluated, as the required scapular compensation to avoid impingements.
  
  
  RESULTS
  With the 36-mm glenosphere, impingements occurred only for rest of hand to back-pocket positions. The 42-mm partly improved the mobility. The 2 lateralized glenospheres were free of impingement. When impingements occurred, the scapular compensation was less than 10°.
  
  
  CONCLUSIONS
  Most reverse prostheses impingements reported in clinical and biomechanical studies can be avoided, either by scapular compensation or by a glenosphere lateralization. After reverse shoulder arthroplasty, a fraction of the mobility of the gleno-humeral is transferred to the scapulo-thoracic joint.
authors: Laboratory of Biomechanical Orthopedics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland. alexandre.terrier@epfl.ch
authors: Alexandre
authors: A
authors: Terrier
authors: Patricia
authors: P
authors: Scheuber
authors: Dominique P
authors: DP
authors: Pioletti
authors: Alain
authors: A
authors: Farron
mesh_terms: D000203:Activities of Daily Living; D000222:Adaptation, Physiological; D019643:Arthroplasty, Replacement / Q000379:methods*; D003198:Computer Simulation; D006801:Humans; D021621:Imaging, Three-Dimensional; D007595:Joint Prosthesis; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016059:Range of Motion, Articular / Q000502:physiology; D012540:Scapula / Q000502:physiology*; D019534:Shoulder Impingement Syndrome / Q000517:prevention & control*; D012785:Shoulder Joint / Q000503:physiopathology / Q000601:surgery