**3. Natural history of anterior instability**

The natural history of anterior shoulder instability has been studied extensively and recurrence has been correlated with a younger age at the time of first dislocation. In a large cohort of 255 patients with primary traumatic anterior dislocation, who were treated with a sling for 4 weeks, there was a 55% incidence of an additional episode of instability within 2 years of the initial traumatic dislocation. Furthermore, 66% of the patients had an episode of instability within 5 years (Robinson et al, 2006). In another study, 324 shoulders were followed for at least 10 years after primary anterior dislocation. Ninety-four percent of the patients younger than 20 years had a recurrence compared with 14% of those older than 40 years. The patients without shoulder immobilization had a 70% recurrence rate that decreased to 26% to 46% when immobilized for 1 to 3 weeks (Rowe, 1956). These findings suggest that younger patients with primary anterior dislocations have a significantly higher rate of recurrence.

The effectiveness of rehabilitation is still in debate. In a study evaluating the effect of rehabilitation, 115 patients with traumatic and atraumatic recurrent shoulder subluxation, underwent a muscle-strengthening exercise regimen (Burkhead & Rockwood, 1992). Sixteen percent of the shoulders with traumatic etiology had excellent or good results in contrast to 80% of those with atraumatic etiology. The authors highlighted the importance of identifying the etiology of instability to ascertain a successful result out of conservative treatment. In a prospective randomized clinical trial, active patients aged less than 30 years who were treated with supervised physical therapy showed recurrence rates of 17 to 96% whereas arthroscopic instability repair had failure rates between 4% and 22% (Bottoni et al, 2002). These findings indicate that young, highly active patients would benefit from early, arthroscopic repair after first-time traumatic anterior shoulder dislocation compared with conventional nonoperative treatment.
