Men are 2.5 times more likely to dislocate a shoulder than women, and the incidence rate is 2.8% of the population. Ninety percent of dislocations are anterior. Over ninety percent of dislocations are due to trauma, but some have inherently lax joints. Some are unstable as a consequence of abnormal neurological control of movement (‘muscle patterning instabilities’) and may respond to prolonged physiotherapy. Left untreated, unstable shoulders will continue to dislocate. Even after surgery approximately 26% will exhibit recurrent instability at 35 years. Arthritis in unstable shoulders arises in 55% at 25 years. Treatment of first time dislocation remains controversial, but a randomised trial of 76 young active patients undergoing surgery for a first time dislocation found a recurrence rate of 3% with surgery against 54% without (Thangarajah and Lambert, 2015).
THANGARAJAH, T. & LAMBERT, S. 2015. Management of the unstable shoulder. Bmj, 350, h2537.