title: Dynamic comparison of segmentary scapulohumeral rhythm between athletes with and without impingement syndrome.
abstract: BACKGROUND
  Patients who have shoulder pain usually have compensatory or contributory deviation of shoulder motion during arm elevation. In the traditional scapulohumeral rhythm, the share of the acromioclavicular (AC) and the sternoclavicular (SC) joint movements and also the role of AC internal rotation angle are unknown.
  
  
  OBJECTIVE
  The main purpose of this study was to measure and compare the segmentary scapulohumeral rhythm (SSHR) during scapular arm elevation at a steady rotational speed in athletes with and without impingement syndrome.
  
  
  METHODS
  Using a speedometer, the maximum speed of arm elevation was measured in 21 men in each of the involved and uninvolved groups. Using fluoroscopy on the dominant side, SSHR during scapular arm elevation at a rotational speed equal to 1/30 of maximum speed was compared between the two groups. The ratio of glenohumeral (GH) elevation angle to AC rotation angle in the scapular plane was considered as SSHR.
  
  
  RESULTS
  The maximum speed of arm elevation between the two groups was significantly different (P < 0.001). The rhythm of the involved group significantly exceeded the rhythm of the uninvolved group in a part of the first quarter range of the arm elevation. SSHR during arm elevation in the uninvolved group did not change significantly (P = 0.845); however, it decreased significantly in the involved group (P = 0.024).
  
  
  CONCLUSIONS
  Speed differences between the two groups were probably due to the pain in some ranges of arm elevation. SSHR in the involved group probably changed in order to compensate downward rotation of the scapula in the resting position. Study of the AC upward rotation range can be misleading; therefore, the study of scapulohumeral rhythm is recommended.
authors.affiliation: Department of Physical Therapy, Faculty of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Cyrus
authors.initials: C
authors.lastname: Taghizadeh Delkhoush
authors.affiliation: Department of Physical Therapy, Faculty of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Nader
authors.initials: N
authors.lastname: Maroufi
authors.affiliation: Department of Physical Therapy, Faculty of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Ismail
authors.initials: I
authors.lastname: Ebrahimi Takamjani
authors.affiliation: School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran.
authors.forename: Farzam
authors.initials: F
authors.lastname: Farahmand
authors.affiliation: Advanced Diagnostic and Interventional Radiology Research Center (ADIR), Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Shakourirad
authors.affiliation: Faculty of Health Management and Information Science, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Hamid
authors.initials: H
authors.lastname: Haghani
keywords: Acromioclavicular Joint; Biomechanical Phenomena; Shoulder Impingement Syndrome