Article

Impingement syndrome is probably the most common cause of shoulder pain. Abnormal abduction and proximal humeral translation are associated
with this condition. We evaluated whether the relative distribution between
glenohumeral and scapular-trunk motions (the scapulohumeral rhythm) and the speed
of motion of the arm differed between patients with impingement and a control
group without shoulder symptoms. METHODS: 30 patients with shoulder
impingement (Neer stage 2) and 11 controls were studied during active abduction
and 21 patients and 9 controls were studied during passive abduction. Dynamic RSA
at a speed of 2 simultaneous exposures per second was used to record the shoulder
motions for 5-6 seconds. RESULTS: Within the interval statistically evaluated
(observations between 20-55 degrees of relative active abduction in the
glenohumeral joint), the patient group showed more scapular and trunk motions (p
= 0.04), especially at up to 40 degrees. The pattern of motion at passive
abduction was somewhat similar to that in the controls. Both controls and
patients showed an increasing absolute (i.e. global) proximal displacement of the
center of the humeral head with increasing active and passive abduction of the
glenohumeral joint and humerus, without any certain difference between the
groups. The mean maximum absolute proximal displacement in the patient and
control groups amounted to about 30 mm and 20 mm, respectively. The corresponding
relative displacement (with fixed scapula) was only 2.0 and 0.5 mm. Active
abduction was initiated with angular velocity of about 50 and 80 degrees per
second, respectively, in the patients and the controls. In both groups it
decreased with progressing abduction down to about 20 degrees per second
(controls) after 3 seconds without there being any statistically significant
difference. The angular velocities at passive abduction showed a similar pattern,
still without any difference. In both groups, the speed of proximal translation
during active abduction peaked 0.5-1 second later than the speed of rotation and
remained relatively even for about 1 second, followed by a deceleration.
INTERPRETATION: We found that the glenohumeral-thoracoscapular ratio during
abduction of the arm in our study, measured as the distribution of motion between
the glenohumeral joint and the trunk in both controls and patients with
impingement, was less than or equal to 1:1. This finding differs from earlier
results, probably due to the use of a method with high resolution and small
influence of motions out of the frontal plane.
The reason for reduced
glenohumeral motions in the early phase of active abduction in the patient group
is uncertain, but pain or avoidance of pain elicited by the motion was probably
of importance.

Langue : ANGLAIS