Chronic anterior glenohumeral instability.

Until relatively recently, discussion of shoulder instability referred only to traumatic and recurrent dislocations. Better clinical diagnosis and improved methods of investigation have now led to the recognition of subtle clinical lesions which present with no true dislocation, and show the increasing requirements of patients and sportsmen. Shoulder instability has become a fully-fledged syndrome, but precise terminology and rigorous classification are essential to obviate confusion. Instability should be considered from the point of view of the patient’s description of symptoms of pain or subluxation. Classification should be based on the frequency, degree, direction and presumed aetiology. Information is gained from an accurate history, which is essential, detailed clinical examination and the numerous tests to establish the distinction between instability and laxity. Standard radiographs and specific views may reveal pathognomonic bone lesions. A purely clinical classification includes three groups: Dislocation. This is a total and permanent loss of contact between the joint surfaces leading to a chronically displaced position of the arm requiring reduction. Subluxation. This is a partial loss of contact, permanent or temporary, at the glenohumeral joint. There can be no precise anatomical definition; the limits of normal excursion of the humeral head remain undefined. The patient describes a feeling of instability and can achieve selfreduction without assistance. It is sometimes difficult to differentiate between dislocation and subluxation, but this has little importance since the anatomical lesions are identical. Pain in the shoulder after an undetected episode of instability. There is no sensation of instability and the patient does not report episodes which suggest dislocation or subluxation. Pain is the sole symptom; it increases during overhead activity of the arm. Various imaging techniques or arthroscopy may reveal typical lesions that confirm instability. Each of these three types of instability can then be classified according to four clinical criteria: direction (anterior or posterior), frequency (acute, recurrent or chronic), aetiology (traumatic or atraumatic, voluntary or involuntary) and structural factors (inferior hyperlaxity) (Table I).