Shoulder instability is a common problem affecting patients most often in their 2nd and 3rd decades of life. Shoulder instability may result in GHJ dislocation, which is displaced anteriorly in 90% of cases. A partial dislocation (subluxation) means the head of the upper arm bone (humerus) is partially out of the socket (glenoid). A complete dislocation means it is all the way out of the socket. Both partial and complete dislocation cause pain and unsteadiness in the shoulder.
Incidence & Prevalence of Shoulder Instability
The risk of sustaining a traumatic anterior dislocation of the shoulder has been estimated at between 1% and 2% over one’s lifetime.
Assessment: Signs and Symptoms
Shoulder instability can be defined as “the loss of shoulder comfort and function due to undesirable translation of the humeral head on the glenoid” (Lippitt et al 1991). Chronic instability causes several symptoms. When the GHJ slips, but does not dislocate, or come completely out of the socket, it is called subluxation. The shoulder may actually feel loose. This commonly happens when the hand is raised above the head. Subluxation of the shoulder usually causes a quick feeling of pain, like something is slipping or pinching in the shoulder. Patients with shoulder instability may experience little or no symptoms. In atraumatic shoulder instability, the first sign of symptoms may be an episode of the shoulder subluxing (i.e. partially dislocating) or shoulder pain or ache either during, or following, certain activities.
A thorough examination from a medical professional is usually sufficient to diagnose shoulder instability. Further investigations such as an X-ray, CT scan, Ultrasound or MRI may be required to assist diagnosis and determine involvement of other structures (such as labral tears, rotator cuff tendonitis or fractures). A recent review of the literature by Monk et al (In Press) concluded that there is no agreement about which validated outcome tool should be used for assessing shoulder instability in patients.
Many treatments have been advocated for these various forms of instability. Most cases of shoulder instability respond well to conservative treatment, involving a limited period of immobilisation in a sling, followed by intensive rehabilitation exercises. Occasionally, surgery may be necessary to repair the loose or torn connective tissue that holds the shoulder in place or to correct other abnormalities associated with the shoulder instability (such as a labral tear or a rotator cuff tear). A Cochrane review concluded that there is evidence to support primary surgery for young adults, usually male, engaged in highly demanding physical activities who have sustained their first acute traumatic shoulder dislocation (Handoll and Al-Maiyah). However there is no evidence available to determine which treatment is better for other patient groups (Handoll and Al-Maiyah). Recent research has also concluded that there is limited evidence regarding the comparative effectiveness of surgical and non-surgical treatment of traumatic aterior shoulder instability, including a lack of evidence regarding the optimal timing of such treatments (Monk et al In Press). This review also highlighted that there is a need for a well-structured randomised control trial to assess the efficacy of surgical and non-surgical interventions for this common type of shoulder instability (Monk et al In Press).
Monk AP et al. Evidence in managing traumatic anterior shoulder instability: a scoping review. Br J Sports Med doi:10.1136/bjsports-2013-092296
Handoll HHG, Al-Maiyah MA. Surgical versus non-surgical treatment for acute anterior shoulder dislocation. Cochrane Database of Systematic Reviews 2004, Issue 1. Art. No.: CD004325. DOI: 10.1002/14651858.CD004325.pub2