Measuring the three-dimensional movement of the scapula provides vital information in
the analysis and treatment of shoulder clinical disorders and contributes to our
understanding of its complex kinematics. However, the thick layer of skin overlying the
scapular region means that all skin-based techniques inaccurately determine the scapular
kinematics. The scapula locator makes use of a palpation technique in order to reduce the
problem of skin deformation. At present, the scapula locator is the most accurate noninvasive
method of measuring scapular movements, but to date the method has only been
used to measure the scapula position statically.
Here, a new method was developed to measure the scapula movements dynamically; the
method makes use of the scapula locator and feedback from pressure-sensors attached to
the locator probes to track the scapula during movement. The reliability of the method
after short-term practise as well as the intra-observer and inter-observer variations and the
inter-session repeatability were tested and quantified in a series of studies.
The method was found to be able to measure dynamic scapular movements in slow to
medium paced arm movements to a good degree of accuracy as well as provide
scapulothoracic measurements of high reliability compared to using the scapula locator
on its own and to previously reported results in the literature.
Finally, the new locator method was used to calibrate the acromial tracker in order to
improve the accuracy of the device and facilitate its use as an alternative to the scapula
locator in clinical studies involving fast (higher than functional velocities) dynamic
activities.
The new scapula locator method and the calibrated acromial tracker method present
significant improvements on the available scapular measurement techniques particularly
in measuring subtle scapular rotations of clinical importance, such as the scapular tilt. The
methods described will be used in future clinical and sport-related studies