Australian Papers - Shoulder Impingement Part 2

Abstract

Shoulder impingement is known by other names, including frozen shoulder. This injury, or condition, has also many origins, and many side-effects, some of which may require surgery to rectify. This series of articles deals with one of the origins which do not require surgery, but which is often misunderstood, or mis-diagnosed, so that surgical intervention is wrongly recommended. The author has worked in the field of manual therapy for more than 25 years, and has conducted studies on treatment of shoulder malfunction for 15 years. During this latter period, the success rate of rectifying those incidents of frozen shoulder presenting at his Newcastle (Australia) clinic exceeded 50%.

The Structure

The shoulder assembly consists of four separate joints; only by considering the existence of, and the duties of each of these four joints will a full understanding emerge. As there are four joints in the shoulder assembly, on each side of the torso – the gleno-humeral, the aromio-clavicular, the sterno-clavicular, and the scapulo-thoracic, I suggest the term “shoulder joint” is no longer meaningful. At this early stage, we will concentrate on one of these joints, the gleno-humeral.

Here is a rear view of the gleno-humeral components, in the “at-rest” position. The red tape represents the vertebral column – note that at rest, the medial border of the scapula is almost parallel with the spine.
Where the rounded head of the humerus meets the shallow dish in the scapula we see the gleno-humeral joint.

Here is another image of the shoulder assembly, again from the rear.In anatomical terms, this is a posterior view, but now the arm has been elevated by a movement called abduction – the arm has been moved away
from the body, by about 45 degrees, and, although the humerus has travelled, the scapula has not. The only joint in action is the gleno-humeral. I have applied a small piece of black tape to the head of the humerus, to draw your attention to a “lump” growing off the bone surface – this is a process, a disfigurement in the bone, meant to act as an attachment point for connective tissue. Its name is the tubercle

In this next image, abduction has been taken a little further, and two things are worth noting – the scapula has still not moved, and, the tubercle is threatening to collide with a ridge of bone that grows, from the scapula, to form what is often referred to as a “roof” over the gleno-humeral joint.
If such a collision occurs, it is commonly called impingement, and significant pain would be experienced – the details of the pain source will be discussed in later chapters, whether it is bone on bone, bone on ligament, or one of the many other possibilities. For now, let’s continue with our study of the joint.

Many skilled surgeons do not grasp the point I am trying to make here – not because it is a difficult concept, and not because they are inept. It is so basic a point, that it is rarely included in University or College teaching programmes.

At this next point in the gleno-humeral journey, the humerus has travelled almost 90 degrees, and at last, the scapula has commenced its downward rotation, averting the risk of collision between the tubercle and the acromion.

Exactly at what point the scapula starts to rotate is (a) debatable, and (b) irrelevant; it’s sufficient for us to appreciate that abduction of the humerus is limited to about 90 degrees or slightly less, depending on the individual.

Impingement will occur if the scapula fails to rotate. Our question is, what prevents this pain-saving rotation.? Or, why doesn’t everyone experience the pain of impingement when they abduct the humerus beyond the horizontal ??

More next week, possums – it’s been a quiet week here, spring is just around the corner, and some productive bird has arranged the production of this never-seen-before flower in my garden – what does bwana think of this ?

BERNARD SCULLY,
NEWCASTLE AUSTRALIA,
SEPTEMBER, 2011