Dislocations of the shoulder occur when the head of the humerus is forcibly removed from its socket in the glenoid fossa. It's possible to dislocate the shoulder in many different directions, and a dislocated shoulder is described by the location where the humeral head ends up after it has been dislocated.Ninety percent or more of shoulder dislocations are anterior dislocations, meaning that the humeral head has been moved to a position in front of the joint. Other rare types of dislocations include luxatio erecta, an inferior dislocation below the joint, and intrathoracic, in which the humeral head gets stuck between the ribs.
Posterior dislocations may be hard to detect on standard AP radiographs, but are more readily detected on other views. After reduction, radiographs are usually repeated to confirm successful reduction and to detect bony damage. After repeated shoulder dislocations, an MRI scan may be used to assess soft tissue damage.Younger patients (teenagers and those aged 20 years) have a much higher frequency of redislocation than patients in their 50s and 60s. Many physicians believe that age is less of a predisposing risk factor for redislocation than activity level.