Shoulder instability and dislocation

luxation The shoulder is a complex part of the body made up of several joints.
The term “dislocation of the shoulder” refers to the dislocation of the scapulo-humeral joint (between the scapula and the humerus)

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Jocelyn-William LOUBRIAT
 
Definition

The shoulder is a complex part of the body made up of several joints.
The term “dislocation of the shoulder” refers to the dislocation of the scapulo-humeral joint (between the scapula and the humerus), meaning the dislocation of the head of the humerus comes out of its location.

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X-ray of a dislocation
source wikipedia commons

If the joint dislocates easily or if the structures maintaining the joint are strained, it is described as “instable”. The term of “laxity” is also used.

Anatomy – physiology

The scapulo-humeral joint is made up by the glenoid fossa or cavity (articular surface of the scapula), the glenoidale labrum (a fibrocartilaginous rim) and the head of the humeral.

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Anatomy of the scapulo-humeral joint

Contrary to the hip, a congruent joint that confers stability (meaning its elements fit closely together), the shoulder confers great mobility to the detriment of perfect stability (non-congruent joint). This stability is mainly provided by the muscles of the “rotators cuff” (Teres minor, infraspinatus, supraspinatus, subscapularis muscles). These muscles provide the coaptation of the aforementioned parts of the joint.

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muscles of the cuff
posterior and anterior

The function of the scapulo-humeral joint among “normal” human beings is either to move an object (carrying a load, and also throwing = open chain), to lean on something or hold oneself (=closed chain), but rarely to maintain a hanging position (open or closed chain using fixed point inversion).
Among homo-climbers, suspension which involves an over-solicitation of the coaptator muscles and therefore needs a perfectly integrated system is the main way of moving.


Mechanismof the lesion

Falls or shocks in most sports are at the origin of scapulo-humeral dislocations. When climbing, shocks are rather rare; but falls (when bouldering) are more common. A wrong position when landing on the arms and the humeral head dislocates. Especially when placing the arms behind, this puts the articulation in a weak position.
However, some dislocations may occur “during a movement” because our activity sometimes imposes special positions on us. If the articular elements are placed in a weak position at the same time certain muscles have strong contractions, the head of the humerus may come out of its location. This was the case with Loïc Gaidioz (interview here). The articulation can also dislocate when the dangling is not controlled the moment you grab a handhold after a dyno (dynamic movement). This happened to Jarno Zwiebel (interview here).
Dislocations are no light injuries and they can sometimes entail severe complications such as the detachment of the labrum (very common as for Loïc), fracture of the head of the humerus (or more rarely of the glenoid), affections of the nerves or the vessels that run in the axilla shallow (under the armpit), or even, as Jarno, stretching of the brachial plexus (in other words of the nerve roots of the arm).


Prevention

It is difficult to prevent a purely “accidental” accident, however the good functioning of the shoulder complex may avoid too much strain on certain structures at the expense of their function. In particular, making sure that the scapula has good mobility may avoid the increase of constraint on the scapulo-humeral joint.
Correction of the physical preparation:
Stretching exercises for all the shoulder muscles: the rhomboid, deltoid, pectoral, latissimus dorsi, biceps and triceps brachii muscles.
It is not possible to relax certain muscles on one’s own. One should therefore consider consulting a physiotherapist for preventive measures, especially since we are not always aware of the limitations of our mobility. An ounce of prevention is worth a pound of cure.

Treatment

Do not try to relocate a dislocation on our own or with the help of somebody else. This medical procedure must be carried out by a doctor, after having checked the entire the joint (no fracture and no nervous or vascular lesion). Trying to relocate it might entail irreversible damage.

After a dislocation without complications, the treatment consists of strict immobilisation, elbow against the body for around 3 to 6 weeks, followed by several weeks of intensive physiotherapy.

When suffering from instability (following an anterior dislocation), the mobility of the shoulder complex should be maintained and actively stabilized by exercising the appropriate muscles. Once again, preventive or maintaining physiotherapy may be better than suffering recurrent incidents.

In cases of frequent recurrences, surgery will be necessary.

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