The main significance of subluxation and dislocation is after the first time, recurrence is very likely, especially in younger patients. The recurrence rate in patients under 20 years old is close to 95%. The recurrence rate goes down as age advances. In patients over age 40, there is only a 40 to 50% recurrence. Backward or posterior dislocation of the shoulder is rare and usually associated with a seizure disorder or high velocity trauma. Backward or posterior subluxation is also relatively rare, and is most often seen in football players, specifically offensive lineman.
Due to the high recurrence rates, the goal of any treatment is to reduce the possibility of recurrence. The minimal treatment for the first time dislocation should be immobilization in a sling and physical therapy for 3-6 weeks. In spite of this treatment, the recurrence rate of dislocation and subluxation is still fairly high. If the shoulder is not immobilized after a dislocation, the chances of redislocation are extremely high with unrestricted activity in the first 1-2 weeks.
Once a shoulder dislocates a second time, it will almost always continue to redislocate with the arm in certain positions and often with less and less trauma.
It is my opinion that once a shoulder subluxes, it will probably continue to do so, even if it is immobilized. If, however, treatment is sought for the first time subluxation, immobilization should be done for 3-6 weeks to take advantage of the off-chance that it will reduce the recurrence rate.