title: Rotator cuff tear pain and tear size and scapulohumeral rhythm.
abstract: BACKGROUND
  The body of knowledge concerning shoulder kinematics in patients with rotator cuff tears is increasing. However, the level of understanding regarding how pain and tear size affect these kinematic patterns is minimal.
  
  
  OBJECTIVE
  To identify relationships between pain associated with a full-thickness rotator cuff tear, tear size, and scapulohumeral rhythm (SHR) and to determine whether pain and tear size serve as predictors of SHR.
  
  
  METHODS
  A test-retest design was used to quantify pain and SHR before and after a subacromial lidocaine injection. Correlation and multivariate analyses were used to identify relationships among pain, tear size, and SHR.
  
  
  METHODS
  Orthopaedic biomechanics research laboratory.
  
  
  METHODS
  Fifteen patients (age range, 40-75 years) with diagnosed full-thickness rotator cuff tears participated. They were experiencing pain at the time of testing.
  
  
  METHODS
  Shoulder kinematic data were collected with an electromagnetic tracking system before and after the patient received a lidocaine injection.
  
  
  METHODS
  Pain was rated using a visual analog scale. Three-dimensional scapular kinematics and glenohumeral elevation were assessed. Scapular kinematics included anterior-posterior tilt, medial-lateral tilt, and upward-downward rotation. A regression model was used to calculate SHR (scapular kinematics to glenohumeral elevation) for phases of humeral elevation and lowering.
  
  
  RESULTS
  Linear relationships were identified between initial pain scores and SHR and between tear size and SHR, representing an increased reliance on scapular motion with increasing pain and tear size. Pain was identified as an independent predictor of SHR, whereas significant findings for the effect of tear size on SHR and the interaction between pain and tear size were limited.
  
  
  CONCLUSIONS
  We noted an increased reliance on scapular contributions to overall humeral elevation with increasing levels of pain and rotator cuff tear size. Pain associated with a rotator cuff tear serves as a primary contributor to the kinematic patterns exhibited in patients with rotator cuff tears.
authors.affiliation: Duquesne University, Department of Athletic Training, Pittsburgh, PA 15282, USA. scibekj@duq.edu
authors.forename: Jason S
authors.initials: JS
authors.lastname: Scibek
authors.forename: James E
authors.initials: JE
authors.lastname: Carpenter
authors.forename: Richard E
authors.initials: RE
authors.lastname: Hughes
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007270:Injections, Intra-Articular; D015601:Injury Severity Score; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010147:Pain Measurement / Q000379:methods*; D017288:Pain Threshold; D016059:Range of Motion, Articular / Q000502:physiology*; D012307:Risk Factors; D000070636:Rotator Cuff Injuries; D012680:Sensitivity and Specificity; D012785:Shoulder Joint / Q000503:physiopathology*; D013180:Sprains and Strains / Q000503:physiopathology
chemical_list: D008012:Lidocaine