title: The minimal detectable change of the Constant score in impingement, full-thickness tears, and massive rotator cuff tears.
abstract: OBJECTIVE
  The purpose of this study was to determine the minimal detectable change (MDC) for the Constant score in patients with impingement, a supraspinatus tear, or a massive rotator cuff (RC) tear as observed changes smaller than the MDC might be the result of measurement error.
  
  
  METHODS
  The Constant score was recorded in a total of 180 patients, including 34 patients with impingement, 105 with supraspinatus tears, and 41 with massive RC tears. We assessed the MDC in the 3 subgroups and total group using the samples standard deviation (SD), internal consistency (Cronbach α), and standard error of the measurement. Floor and ceiling effects were also reported.
  
  
  RESULTS
  The absolute mean Constant score was 72 (SD, 11.2) in the impingement group, 44 (SD, 14.7) in the supraspinatus tear group, and 46 (SD, 18.9) in the massive RC tear group. There were no floor and ceiling effects for the absolute Constant score. In the total group, the internal consistency was 0.8 and the standard error of the measurement was 8. The MDC was 23 points on the Constant score in the total group and 17, 18, and 23 points on the Constant score for impingement, RC tears, and massive RC tears, respectively.
  
  
  CONCLUSIONS
  This study demonstrates that the MDCs of the Constant score are different in patients with impingement, supraspinatus tears, and massive RC tears. Studies reporting the Constant score should be interpreted by use of the population-specific MDC and minimal clinical important change.
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands; Laboratory for Kinematics and Neuromechanics, Leiden University Medical Center, Leiden, The Netherlands. Electronic address: j.f.henseler@lumc.nl.
authors.forename: Jan Ferdinand
authors.initials: JF
authors.lastname: Henseler
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands; Laboratory for Kinematics and Neuromechanics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Arjen
authors.initials: A
authors.lastname: Kolk
authors.affiliation: Department of Orthopaedic Surgery, Medical Center Haaglanden, Den Haag, 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: Jochem
authors.initials: J
authors.lastname: Nagels
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Thea P M
authors.initials: TP
authors.lastname: Vliet Vlieland
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Rob G H H
authors.initials: RG
authors.lastname: Nelissen
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007592:Joint Diseases / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D017006:Rotator Cuff / Q000601:surgery; D000070636:Rotator Cuff Injuries; D012421:Rupture; D019534:Shoulder Impingement Syndrome / Q000175:diagnosis*; D013708:Tendon Injuries / Q000175:diagnosis*
keywords: Constant score; Minimal detectable change (MDC); minimal clinical important difference (MCID); minimal important change (MIC); rotator cuff; shoulder