Scapular Alignment & Shoulder Impingement

Most clinicians involved in treating shoulder impingement syndromes acknowledge the role of scapulo-thoracic joint alignment in impingement patients.  The clinical challenges is to determine the relevance of postural symmetries in the shoulder girdle as part of the pathology. Clinicians will be aware of the two broad distinctions in shoulder impingement pathology as being either primary or secondary mechanisms.

Primary mechanisms relate to factors which reduce the subacromial space resulting in encroachment on the intervening tissues.

Secondary impingements do not result from space occupying pathology such as:

Osteophyytes

Tendon thickening,

AC joint mal-alignment,

Osseous anomalies in the acronimal shape.

These are variable parameters, which a treating therapist must evaluate in order to determine their relevance (or not) in the mechanism of impingement pain.

Understanding patterns of motion is essential if we are trying to determine relevant malalignment.  American physiotherapist Shirley Sahrmann in her classic text ‘Movement Impairment Syndromes’ describes a group of scapular mal-alignments associated with impingement together with a description of the functional anatomy and pathophysiology associated.

These include:

Superior scapular migration syndrome

Inferior scapular migration syndrome

Downward scapular rotation syndrome

Winging scapular syndrome

Anterior tilt

Scapular protraction.

The net result of variations in scapular position as outlined above alter the alignment of the Humerus relative to the Glenoid or perhaps more correctly, the Glenoid relative to the Humerus. This altered mechanical relationship produces changes in the length- tension characteristics of the relevant muscles of the scapular thoracic and rotator cuff complexes.  Such malalignments may alter either the antero-posterior force couple across the Gleno-humeral joint, or as is more traditionally perceived alter the superior inferior force couple across the joint with a potential for superior Humeral migration.

The challenge for the therapist in clinical practice is to….

1.       Determine the existence of the mal-alignment

2.       Identify the predominant mechanism behind this malalignment.

.

Having determined the existence of one or both of these features, then the key issue is to determine its relevance.

The relevance can be ascertained by passively correcting the perceived / hypothesised mal-alignment or facilitating movement with the mal-alignment corrected.

Changes in the objective clinical signs confirm or refute  the clinical hypothesis of “scapular contribution” to shoulder impingement