1.1.1 Macro-traumatic Anterior Instability
- In traumatic anterior instability, the history is usually one of contact with the arm in 90° or
above, such as a fall, collision or tackling incident where the arm is forced back into a
combination of elevation, external rotation +/- extension (McCluskey & Getz, 2000).
This mechanism of injury is very typical of a sporting scenario but could also occur
in a workplace or home setting. - In traumatic anterior instability, particularly in a high-speed collision scenario, the humeral
head will dislocate anterior-inferiorly, creating damage to the anterior-inferior capsuloligamentous
and labral complex, plus or minus the anterior glenoid rim (Boney Bankart lesion)
and/or posterior humeral head (Hills-Sachs lesion). - If the HH locks out, (HH shifts over the glenoid rim and does not spontaneously reduce;
grade 3+) then it will need to be reduced (relocated) and the patient may report having to
have their shoulder relocated or “put back in” either by someone present at the scene or
in hospital (plus or minus the use of anaesthetic). In other scenarios, the HH may
spontaneously reduce once the patient moves, particularly if the underlying joint is hypermobile. - In some other macro-traumatic situations, the GHJ may not dislocate, but sublux, where
the humeral head has translated enough to almost come out over the glenoid rim but
fails to meet a grade 3+ dislocation. - A traumatic subluxation can also result in damage to the anterior inferior capsuloligamentous
and labral complex, plus or minus injury to the anterior glenoid rim and/or humeral head. - In some, less common scenarios, an anterior dislocation or subluxation in lesser ranges
of elevation, such as a collision or fall with the arm tucked in by the patient’s side. - In some situations, the HH can be displaced more anterior superiorly. Examples
include a fall onto the point of the elbow (which drives the HH anterosuperior) or a fall onto
an outstretched arm with the arm behind the body ( e.g. slipping over on ice). This can
result in a traumatic SLAP lesions or combined SLAP and superior glenohumeral
ligament (SGHL). - Patients with macro-traumatic anterior instability will typically report apprehension,
weakness, positional specific pain, and/or avoidance in combined positions of abduction
and ER at 90° of elevation; such as reaching back behind their head or getting their arm
back to throw a ball (see more in aggravating factors and symptomology section).