title: Full can test: Mechanisms of a positive test in patients with shoulder pain.
abstract: BACKGROUND
  The full can test is theorized to produce compressive loads on the supraspinatus tendon within the subacromial space. Characterizing the width of the subacromial outlet, scapular orientation, and shoulder pain during the full can test will improve the mechanistic understanding of the positive full can test.
  
  
  METHODS
  Cross-sectional repeated measures design. Participants with subacromial pain syndrome (n=30) were compared to a matched control group (n=30) during 2 conditions: passive support, and the full can test. The full can test was performed with the arm elevated to 90° in the scapular plane. In both conditions, measurements were taken of acromiohumeral distance with ultrasonography, scapular position using electromagnetic tracking, shoulder strength using a dynamometer, and shoulder pain with the 11-point rating scale.
  
  
  RESULTS
  During the full can test, both groups had a decreased acromial humeral distance, scapular upward rotation, posterior tilt, external rotation and clavicular protraction as compared to passive support (p<0.05). The subacromial pain group as compared to the control group reported greater shoulder pain (p<0.001), reduced strength (p=0.002) and greater scapular anterior tilt (p<0.05) during the full can test.
  
  
  CONCLUSIONS
  This study indicates the mechanisms of a full can test are a reduction in the acromial humeral distance, accompanied by scapular kinematic changes. A positive test of increased pain and reduced strength in those with subacromial pain syndrome can be explained additionally by an increase in scapular anterior tilt. These mechanistic changes may lead to tendon compression, but this cannot be verified as direct tendon compression was not measured.
authors.affiliation: School of Kinesiology, College of Health Professions, Marshall University, Huntington, WV 25703, USA. Electronic address: timmonsm@marshall.edu.
authors.forename: Mark K
authors.initials: MK
authors.lastname: Timmons
authors.affiliation: Dokuz Eylul University, School of Physical Therapy and Rehabilitation, Inciralti Saglik Yerleskesi, Balcova, 35340 Izmir, Turkey.
authors.forename: Sevgi S
authors.initials: SS
authors.lastname: Yesilyaprak
authors.affiliation: Department of Veterans Affairs-Hunter Holmes McGuire VA Medical Center, Physical Medicine and Rehabilitation Section, Richmond, VA 23249, USA.
authors.forename: Jeff
authors.initials: J
authors.lastname: Ericksen
authors.affiliation: Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, USA.
authors.forename: Lori A
authors.initials: LA
authors.lastname: Michener
mesh_terms: D000174:Acromion / Q000503:physiopathology; D000328:Adult; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology; D017006:Rotator Cuff / Q000000981:diagnostic imaging; D012540:Scapula / Q000000981:diagnostic imaging; D019534:Shoulder Impingement Syndrome / Q000175:diagnosis* / Q000503:physiopathology; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000503:physiopathology; D020069:Shoulder Pain / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D055815:Young Adult
keywords: Acromial humeral distance; Full can test; Scapular position; Shoulder; Subacromial pain; Ultrasonography