effect on scapula 3-dimensional posture and kinematics in healthy male and
female populations

C, Croisier JL, Rigaux E, Denoel V, Bruls O, Forthomme B. J Shoulder Elbow
Surg. 2013: S1058-2746(13)00449-7.

Take Home Message:  Healthy individuals exhibit subtle but
significant asymmetries between the dominant and nondominant scapula during
glenohumeral motion.  Therefore, we
should be cautious when using the contralateral shoulder as a reference.

dyskinesis is an umbrella term describing abnormal scapular movement and
kinematics, associated with various shoulder injuries including rotator cuff
syndrome, impingement syndrome, and shoulder instability. When we evaluate
scapular dyskinesis we often compare the pathologic side with the contralateral
shoulder but this assumes that scapular movement is symmetrical between sides
in healthy individuals, which may not be the case. Schwartz et al. investigated
the effect of gender and type of glenohumeral motion on 3-dimensional scapular
motion bilateral symmetry in healthy populations, with the hypothesis that sex
and type of motion would influence symmetry. The authors recruited 22 volunteers without any complaints of shoulder
pain and no history of participation in sports using the upper extremity (11
men and 11 women; mean age of ~22 years). An examiner evaluated the
participants and ruled out any postural abnormalities, pathology or prior
surgeries involving the upper extremities or spine, and any sub-coracoacromial
or tendinous pathologies.  The authors
tracked the 3 dimensional position and movement of the scapulae as the
participant performed 3 motions for their dominant side: abduction in the
frontal plane, flexion in the sagittal plane, and glenohumeral internal/external
rotation with the arm abducted at 90 degrees and the elbow flexed at 90 degrees.
The participants had symmetrical resting positions for their scapula; however,
among men the dominant scapula may be a little more laterally or medially
positioned (0.5 cm) compared with the nondominant scapula. Despite similar
resting positions, the authors observed asymmetrical scapular motion during
glenohumeral movements, especially glenohumeral flexion and abduction. Males
tended to have more upward rotation of the dominant scapula compared with the
nondominant side during glenohumeral elevation. Meanwhile, women had
differences related to internal/external rotation and more upward rotation of
the dominant scapula during glenohumeral elevation.

We can
draw several conclusions with important clinical ramifications from this study.
For one, since subtle scapular asymmetries may exist in the healthy population,
clinicians should be parsimonious with treatment in the absence of symptoms;
such as, pain and range of motion deficits. Furthermore, until the threshold
between normal and abnormal asymmetries can be defined, one should be cautious
in classifying these scapular asymmetries as pathology. Additionally, the
authors found the scapulae can be fairly symmetrical in a resting position,
which may highlight a kinematic origin for scapular asymmetries. Since previous
research has implicated postural differences, particularly among an athletic population, we may still need
to consider the resting scapula position when developing a rehabilitation
regimen for our patient. The authors note there are difficulties to
extrapolating the data from the current participants to other clinical
populations given the influence of age, sex, and level of physical activity. Regardless
of these limitations, one should be careful when using the contralateral
shoulder as a reference given the inherent subtle differences in scapular
motion between dominant and non-dominant sides. 

Questions for Discussion: How do you
tailor rehabilitation regimens to patients with differences in scapular motion
between the dominant and nondominant sides? What impact of age, sex, and level
of physical activity have you noted on your own clinic populations?

by: Jason Brucker, MD; Kris Fayock, MD
by: Jeffrey Driban


Schwartz C, Croisier JL, Rigaux E, Denoël V, Brüls O, & Forthomme B (2013). Dominance effect on scapula 3-dimensional posture and kinematics in healthy male and female populations. Journal of Shoulder and Elbow Surgery PMID: 24280354