Glenohumeral instability of the shoulder joint becomes a new clinical unit recently. An existence of glenohumeral instability is bound on an excessive motility of the head of the humerus towards the articular capsule. The excessive motility of the head of the humerus is not caused by a damage of the cotyle3, but mainly others, for stabilization of the glenohumeral articulation important structures which are :
tendinous – muscular apparatus, i.e. mainly muscles of the rotator cuff
which under the normal circumstances prevent to excessive movements. If their stabilizing function is impaired, subluxations or luxations of the head of the humerus with a following trauma of a surrounding soft component occur.
A prototype of this affection is a classical acute luxation of the glenohumeral articulation of traumatic etiology with a typical picture.
Picture of the luxation of the glenohumeral articulation
Ultrasound picture and scheme of the luxation of the
videoclip of the luxation of the glenohumeral articulation
X-ray picture of the luxation of the glenohumeral articulation
X-ray picture of the state after reattachment of the luxation
Similar changes as at acute luxation of the glenohumeral articulation4 also originate at instability and chronic subluxations where the changes are of course smaller. Small traumas of labrum glenoidale or changes in the stabilizing function of the rotator cuff can be the causes of the excessive motility of the glenohumeral articulation. A principle of the disorder is a slipping of the head of the humerus out of the cotyle in a certain position on which basis a trauma of the rotator cuff and articular capsule occurs. This situation is mostly coming during movements in extreme positions. An example of this movement can be a throwing the javelin etc. Affected people sometimes feel the slipping of the joint, and sometimes a blockade of the shoulder. But at some persons these subluxations are also developing during normal everyday activities, rather on the basis of a congenital laxity of the articular capsule, or in terrain where an injury damaged the stabilizing structures of the shoulder joint. The instability of the glenohumeral articulation can manifest itself at one level of the movement, or it can affected more directions all at once.
The instability of the shoulder joint can be bound only on one direction, or it can affect more of them. With regarding to the firm roof of the acromion, which is over the head of the humerus, and prevent to the dislocation in the direction upwards, only following directions of instability or eventual luxation are possible.
3it is too shallow to have a fundamental meaning for the stabilization of the shoulder joint
4even if of course more discreet