Biomedical Engineering Reference
In-Depth Information
shoulder movements are still incredibly difficult to
standardize. Indeed, the shoulder complex groups together
several joints: the sterno-clavicular (between the sternum
and clavicle), acromioclavicular (between the clavicle and
scapula), scapulothoracic (between the scapula and thorax)
and the glenohumeral (between the scapula and humerus)
joints. Some studies consider the shoulder complex as a
whole, by referring to the relative rotations of the arms with
regard to the thorax [PET 07]; however, from a clinical point
of view, it is often useful to characterize scapulothoracic and
glenohumeral joint movements separately. In this case,
monitoring the scapula using non-invasive motion analysis
systems is tricky. The acromial method [MES 07, ŠEN 10],
involves placing a set of three markers, which define the
scapula segment, close to the acromion to limit measurement
errors caused by soft tissues; Brochard
et al.
[BRO 11]
showed that using a double calibration, at both extreme
positions of the movement analyzed (Figure 5.6), further
improves the accuracy of the scapula movement, making the
results acceptable in a clinical context (with a mean
quadratic error between 3 and 4.5°). In the literature review
by Lempereur
et al.
on this subject [LEM 14], 19 studies that
assessed the accuracy and repeatability of six methods
designed to monitor the scapula using cutaneous markers
have been analyzed and these authors recommended the
acromial method, specifying that beyond a 90° elevation of
the arm, using multiple calibration [PRI 11] further
improves this accuracy.
Another difficulty with respect to the shoulder complex is
its high mobility in all planes, which makes the choice of the
rotation sequence impossible to generalize when studying its
motion. To analyze the overall movements of the shoulder
complex, Bonnefoy
et al.
[BON 10] proposed, depending on
the motion studied, to take preference of a sequence for
which the floating axis corresponds to the lowest amplitude
of movement. To report the angles of the glenohumeral joint,
