Acromiohumeral distance and scapular position
It is generally believed that overhead athletes develop pathologic shoulder conditions as a result of both long and short term adaptations leading to a narrowed subacromial space. To gain more insight in this matter, the acute changes in acromiohumeral distance and 3-D scapular position after an overhead fatigue protocol were determined. Surprisingly, AHD increased and posterior tilt and upward and external rotation of the scapula increased.
Pathologic conditions of the shoulder joint are frequently seen overhead athletes. It is commonly believed that adaptations – resulting from exposure to repetitive overhead motion at high velocities – are causing the subacromial space to narrow. This in turn leaves only little room for the rotator cuff tendons, especially in elevation.
In order to gain insight in acute changes in acromiohumeral distance (AHD) and 3-D scapular position after fatigue due to high velocity overhead movements, 29 healthy overhead athletes underwent measurements of the AHD and 3-dimensional scapular position prior to and directly after an overhead fatigue protocol. AHD was determined for the dominant as well as the non-dominant side using ultrasound; 3-D scapular positions were collected using an electromagnetic motion-tracking system.
No differences in AHD and 3-D scapular position between the normal and fatigued state were observed with the arm in 0 degrees of abduction. At 45 and 60 degrees of abduction, the AHD increased and correspondingly, the scapula was more posteriorly tilted, upwardly and externally rotated – the opposite of what was expected.What could be the underlying mechanism behind these changes that seemingly contradict the current consensus in clinical practice?
> From: Maenhout et al., J Athl Train 50 (2015) 281-288. All rights reserved to the National Athletic Trainers’ Association, Inc. Click here for the Pubmed summary.