title: Three-dimensional shoulder kinematics normalize after rotator cuff repair.
abstract: BACKGROUND
  Patients with a rotator cuff (RC) tear often exhibit scapular dyskinesia with increased scapular lateral rotation and decreased glenohumeral elevation with arm abduction. We hypothesized that in patients with an RC tear, scapular lateral rotation, and thus glenohumeral elevation, will be restored to normal after RC repair.
  
  
  METHODS
  Shoulder kinematics were quantitatively analyzed in 26 patients with an electromagnetic tracking device (Flock of Birds) before and 1 year after RC repair in this observational case series. We focused on humeral range of motion and scapular kinematics during abduction. The asymptomatic contralateral shoulder was used as the control. Changes in scapular kinematics were associated with the gain in range of motion. Shoulder kinematics were analyzed using a linear mixed model.
  
  
  RESULTS
  Mean arm abduction and forward flexion improved after surgery by 20° (95% confidence interval [CI], 2.7°-36.5°; P = .025) and 13° (95% CI, 1.2°-36.5°; P = .044), respectively. Kinematic analyses showed decreases in mean scapular protraction (ie, internal rotation) and lateral rotation (ie, upward rotation) during abduction by 3° (95% CI, 0.0°-5.2°; P = .046) and 4° (95% CI, 1.6°-8.4°; P = .042), respectively. Glenohumeral elevation increased by 5° (95% CI, 0.6°-9.7°; P = .028) at 80°. Humeral range of motion increased when scapular lateral rotation decreased and posterior tilt increased.
  
  
  CONCLUSIONS
  Scapular kinematics normalize after RC repair toward a symmetrical scapular motion pattern as observed in the asymptomatic contralateral shoulder. The observed changes in scapular kinematics are associated with an increased overall range of motion and suggest restored function of shoulder muscles.
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands; Laboratory for Kinematics and Neuromechanics, Department of Orthopaedics and Rehabilitation, Leiden University Medical Center, Leiden, The Netherlands. Electronic address: a.kolk@lumc.nl.
authors.forename: Arjen
authors.initials: A
authors.lastname: Kolk
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands; Laboratory for Kinematics and Neuromechanics, Department of Orthopaedics and Rehabilitation, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Pieter Bas
authors.initials: PB
authors.lastname: de Witte
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands; Laboratory for Kinematics and Neuromechanics, Department of Orthopaedics and Rehabilitation, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Jan Ferdinand
authors.initials: JF
authors.lastname: Henseler
authors.affiliation: Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Erik W
authors.initials: EW
authors.lastname: van Zwet
authors.affiliation: Department of Orthopaedic Surgery, Medical Center Haaglanden, The Hague, The Netherlands.
authors.forename: Ewoud R A
authors.initials: ER
authors.lastname: van Arkel
authors.affiliation: Department of Orthopaedic Surgery, Medical Center Haaglanden, The Hague, The Netherlands.
authors.forename: Peer
authors.initials: P
authors.lastname: van der Zwaal
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Rob G H H
authors.initials: RG
authors.lastname: Nelissen
authors.affiliation: Laboratory for Kinematics and Neuromechanics, Department of Orthopaedics and Rehabilitation, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Jurriaan H
authors.initials: JH
authors.lastname: de Groot
mesh_terms: D000368:Aged; D001178:Arthroplasty; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D017006:Rotator Cuff / Q000503:physiopathology* / Q000601:surgery; D000070636:Rotator Cuff Injuries / Q000503:physiopathology* / Q000601:surgery; D012540:Scapula / Q000503:physiopathology* / Q000601:surgery; D012782:Shoulder / Q000503:physiopathology* / Q000601:surgery; D012785:Shoulder Joint / Q000503:physiopathology* / Q000601:surgery
keywords: Rotator cuff; kinematics; kinesiology; movement; shoulder; surgery; tears