Atraumatic Shoulder Instability.
Last updated Thursday, February 10, 2005
Figure 2 - Age distribution of atraumatic instability patients Figure 3 - SST functional deficits: AMBRII patients HistoryWhat is the age distribution for atraumatic glenohumeral instability? The age distribution of 51 patients presenting to our service with the
atraumatic (AMBRII) instability shows that this appears to be a
condition which presents predominantly under the age of 30 (see figure
2).What causes atraumatic glenohumeral instability? AMBRII instability often begins with some minor event or series of
events which lead to progressive decompensation of the glenohumeral
stability mechanisms.
An awkward lift, reaching over the back seat of the car, or a sneeze
may be all that is necessary to launch the predisposed, but
compensated, shoulder down the path toward instability. The patient
notices that the shoulder has become loose and may feel it slip out and
clunk back in with different activities. These episodes almost never
require manipulative reduction.
The instability may be sufficiently subtle that the patient is
unaware of the humerus translating on the glenoid. The patient may only
be aware of a feeling that the shoulder does something unnatural in
certain positions, or that certain functions cannot be performed, such
as reaching out in front or lifting at the side.
In contrast to the situation in traumatic instability, discomfort
with activities of daily living may be a significant component of the
complaint. A patient may volunteer that he or she can make the shoulder
"pop out" and that at times the shoulder feels as if it "needs to be
popped out" on purpose.
The patient should indicate each and every position in which
problems with instability have been noted. Instability with the arm out
in front of the body and problems lifting or reaching down are
particularly suggestive of the AMBRII condition. It is important to
note how frequently the problem occurs and whether the problem is
"avoidable" if the patient concentrates on how the shoulder is used.
Finally, we record the extent and effectiveness of previous
non-operative and operative treatment and the presence or absence of
instability symptoms in the opposite shoulder or other joints.
How does the Simple Shoulder Test (SST) aid in understanding atraumatic multidirectional glenohumeral instability The Simple Shoulder Test provides a minimal data set for
characterizing some of the functional impairment from atraumatic
multidirectional glenohumeral instability. These patients had greatest
difficulty sleeping, lifting overhead, and throwing (see figure 3).
Particular emphasis is placed on the patient's functional goals with
respect to work and sport. We try to determine whether these goals are
realistic, considering the condition of the shoulder. Summary In summary, patients with atraumatic instability are usually young,
perhaps with a family predisposition to "loose shoulders." The
instability is most prevalent in midrange positions, those commonly
used in activities of daily living, such as lifting at the side or
raising the arm to the front. The contralateral shoulder may also seem
"loose." The patient may have difficulty defining exactly what it is
about the shoulder that is bothersome. The history does not reveal an
injury of sufficient magnitude to tear the capsule or ligaments.
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