Effects of scapular dyskinesis and scapular assistance test on subacromial space during static arm elevation.

Seitz AL, McClure PW, Lynch SS, Ketchum JM, Michener LA. J Shoulder Elbow Surg. 2011 Mar 26. [Epub ahead of print]

Scapular dyskinesis has been defined as an alteration in the motion and position of the scapula during arm elevation. It has been observed in patients with shoulders injuries including impingement syndrome and rotator cuff tears. The commonly observed altered scapular motions are decreased upward rotation, posterior tilt, and increased external rotation. These altered motions have been suggested to cumulatively decrease the subacromial space and cause compression of the supraspinatus tendon. The scapular assistance test (SAT) is a new clinical test that is designed to identify if there is scapular involvement associated with impingement syndrome. The SAT involves the clinician passively assisting scapular upward rotation and posterior tilt during arm elevation. A positive test is if the corrective action ameliorates the patient’s symptoms. However, it has not been determined if the SAT actually increases these motions and the subacromial space during arm elevation. This study divided 40 asymptomatic participants into two groups (20 obvious dyskinesis and 20 normal motion). Scapular motion was measured using a magnetic tracking system and the subacromial space was measured with a diagnostic ultrasound at rest, 45°, and 90° of arm elevation. All subjects were evaluated both with and without the SAT. The results indicate that there were no differences between groups for scapular kinematics or subacromial space. The SAT was found to increase upward rotation, posterior tilting, and subacromial space in both groups. The dyskinesis group had more upward rotation during the SAT compared to the normal motion group. 

This study evaluated the effectiveness of a new clinical test used to determine the amount of scapular involvement in subacromial impingement. It also examined scapular kinematics and subacromial space between a group with dyskinesis compared to normal controls. These results indicate that the SAT is effective at increasing the subacromial space by increasing scapular upward rotation and posterior tilting. On average the subacromial space was only increased by 1.8 mm and it is difficult to determine if this is clinically significant due to the measurement error being 1.1 mm. It also found that subjects with dyskinesis do not have any alterations in the measured scapular kinematics or subacromial space. This is in disagreement with other studies and suggests that these variables may not be altered even when obvious dyskinesis is present. Unlike other studies subjects did not present with shoulder pain or symptoms so the role of pain may need to be further investigated to determine if alterations are only associated in symptomatic patients. Clinically, this suggests that the SAT will increase scapular upward rotation and posterior tilting, although it is still unclear if the amount of subacromial space is a cause of shoulder injury or a consequence. Personally I have great success with the SAT to determine if patients suffering from impingement syndrome will benefit from scapular rehabilitation. What are your experiences?

Written by: Stephen Thomas
Reviewed by: Jeffrey Driban