title: Subacromial anaesthetics increase asymmetry of scapular kinematics in patients with subacromial pain syndrome.
abstract: BACKGROUND
  Subacromial pain syndrome (SAPS) and scapular dyskinesis are closely associated, but the role of pain is unknown. We hypothesized that pain results in asymmetrical scapular kinematics, and we expected more symmetrical kinematics after infiltration of subacromial anaesthetics.
  
  
  OBJECTIVE
  To investigate the effect of subacromial anaesthetics on scapular kinematics in patients with SAPS.
  
  
  METHODS
  Observational cohort study.
  
  
  METHODS
  We evaluated shoulder kinematics in 34 patients clinically and radiologically (magnetic resonance arthrography) identified with unilateral SAPS using three-dimensional electromagnetic motion analysis (Flock of Birds). Scapular internal rotation, upward rotation and posterior tilt of the affected shoulder were compared with the kinematics of the unaffected shoulder and following subacromial anaesthetics. Additionally, the association of pain (Visual Analogue Scale, VAS) and scapular rotation was analysed.
  
  
  RESULTS
  Compared with the contralateral healthy shoulder, 5° more (95% CI 0.4-9.7, p = 0.034) scapular internal rotation was observed in the affected shoulder at 110-120° of abduction. Following subacromial anaesthetics in the affected shoulder, internal rotation increased (2°, 95% CI 0.5-3.9, p = 0.045) and posterior tilt decreased (3°, 95% CI 1.5-5.0, p = 0.001) at 110-120° of abduction. Less scapular upward rotation was significantly associated with higher pain scores before infiltration (R = 0.45, p = 0.013).
  
  
  CONCLUSIONS
  More scapular internal rotation was observed in affected shoulders of patients with SAPS compared with unaffected shoulders. Subacromial infiltration did not restore kinematics toward symmetrical scapular motion. These findings suggest that subacromial anaesthesia is not an effective means to instantly restore symmetry of shoulder motion.
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postzone J11R, PO Box 9600, 2300RC Leiden, the Netherlands; Laboratory for Kinematics and Neuromechanics, Leiden University Medical Center, Postzone J11R, PO Box 9600, 2300RC 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, Postzone J11R, PO Box 9600, 2300RC Leiden, the Netherlands; Laboratory for Kinematics and Neuromechanics, Leiden University Medical Center, Postzone J11R, PO Box 9600, 2300RC Leiden, the Netherlands.
authors.forename: Jan Ferdinand
authors.initials: JF
authors.lastname: Henseler
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postzone J11R, PO Box 9600, 2300RC Leiden, the Netherlands; Laboratory for Kinematics and Neuromechanics, Leiden University Medical Center, Postzone J11R, PO Box 9600, 2300RC Leiden, the Netherlands.
authors.forename: Pieter Bas
authors.initials: PB
authors.lastname: de Witte
authors.affiliation: Department of Orthopaedic Surgery, Medical Center Haaglanden, Postzone A2-72, PO Box 432, 2501CK The Hague, the Netherlands.
authors.forename: Ewoud R A
authors.initials: ERA
authors.lastname: van Arkel
authors.affiliation: Department of Orthopaedics, Rijnland Hospital, PO Box 4220, 2350CC Leiderdorp, the Netherlands.
authors.forename: Cornelis P J
authors.initials: CPJ
authors.lastname: Visser
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postzone J11R, PO Box 9600, 2300RC Leiden, the Netherlands.
authors.forename: Jochem
authors.initials: J
authors.lastname: Nagels
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postzone J11R, PO Box 9600, 2300RC Leiden, the Netherlands.
authors.forename: Rob G H H
authors.initials: RGHH
authors.lastname: Nelissen
authors.affiliation: Laboratory for Kinematics and Neuromechanics, Leiden University Medical Center, Postzone J11R, PO Box 9600, 2300RC Leiden, the Netherlands.
authors.forename: Jurriaan H
authors.initials: JH
authors.lastname: de Groot
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000777:Anesthetics / Q000009:adverse effects*; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D020820:Dyskinesias / Q000209:etiology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology*; D017006:Rotator Cuff / Q000503:physiopathology*; D012540:Scapula / Q000503:physiopathology*; D019534:Shoulder Impingement Syndrome / Q000139:chemically induced*
chemical_list: D000777:Anesthetics
keywords: Impingement syndrome; Kinematics; Pain; Rotator cuff; Scapula; Shoulder