title: Three-Dimensional Scapular Kinematics in Patients with Reverse Total Shoulder Arthroplasty during Arm Motion.
abstract: BACKGROUND
  There have been few reports on altered kinematics of the shoulder after reverse total shoulder arthroplasty (RTSA). We investigated differences in 3-dimensional (3D) scapular motions assessed using an optical tracking system between RTSA treated shoulders and asymptomatic contralateral shoulders during arm motion.
  
  
  METHODS
  Thirteen patients who underwent RTSA were assessed for active arm elevation in 2 distinct elevation planes (sagittal plane flexion and scapular plane abduction). Their mean age was 72 years (range, 69 to 79 years) and the mean follow-up was 24.4 months (range, 13 to 48 months). The dominant side was the right side in all the 13 patients, and it was also the side treated with RTSA. Scapular kinematics was recorded with an optical tracking system. The scapular kinematics and the scapulohumeral rhythm (SHR) of the RTSA shoulders and asymptomatic contralateral shoulders were recorded and analyzed during arm elevation.
  
  
  RESULTS
  There were no significant differences in internal/external rotation and anterior/posterior tilting of the scapula between shoulders during arm motion (p > 0.05). However, upward rotation of the scapula differed significantly during arm motion (p = 0.035 for sagittal plane flexion; p = 0.046 for scapular plane abduction). There were significant differences in the SHR between the two shoulders (p = 0.016 for sagittal plane flexion; p = 0.021 for scapular plane abduction).
  
  
  CONCLUSIONS
  The shoulder kinematics after RTSA showed significant differences from the contralateral asymptomatic shoulders. Increased upward rotation and decreased SHR after RTSA indicate that RTSA shoulders use more scapulothoracic motion and less glenohumeral motion to elevate the arm.
authors: Department of Orthopedic Surgery, Eulji University School of Medicine, Daejeon, Korea.
authors: Kwang Won
authors: KW
authors: Lee
authors: Department of Orthopedic Surgery, Sewoori Hospital, Daejeon, Korea.
authors: Yong In
authors: YI
authors: Kim
authors: Department of Orthopedic Surgery, Eulji University School of Medicine, Daejeon, Korea.
authors: Ha Yong
authors: HY
authors: Kim
authors: Department of Orthopedic Surgery, Eulji University School of Medicine, Daejeon, Korea.
authors: Dae Suk
authors: DS
authors: Yang
authors: Department of Orthopedic Surgery, Eulji University School of Medicine, Daejeon, Korea.
authors: Gyu Sang
authors: GS
authors: Lee
authors: Department of Orthopedic Surgery, Eulji University School of Medicine, Daejeon, Korea.
authors: Won Sik
authors: WS
authors: Choy
mesh_terms: D000368:Aged; D001132:Arm / Q000502:physiology; D000072228:Arthroplasty, Replacement, Shoulder / Q000379:methods*; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D005260:Female; D057918:Fiducial Markers; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D016059:Range of Motion, Articular / Q000502:physiology*; D012540:Scapula / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*
keywords: 3D scapular motions; Optical tracking system; Reverse total shoulder arthroplasty; Scapulohumeral rhythm; Shoulder