Background: The epidemiology of traumatic shoulder dislocations is poorly understood. The aim of the current study was to determine the incidence of shoulder dislocations presenting to hospital emergency departments in the United States and define demographic risk factors for these injuries.
Methods: The National Electronic Injury Surveillance System, a probability sample of all injuries presenting to emergency departments in the United States, was queried for shoulder dislocations from 2002 through 2006. Patient and injury characteristics were analyzed. United States Census data were utilized to calculate incidence rates for the United States population and subgroups. Incidence rate ratios were then calculated with respect to age, sex, and race.
Results: A total of 8940 shoulder dislocations were identified, resulting in an overall incidence rate in the United States of 23.9 (95% confidence interval, 20.8 to 27.0) per 100,000 person-years. The male incidence rate was 34.90 (95% confidence interval, 30.08 to 39.73) per 100,000 person-years, with an incidence rate ratio of 2.64 (95% confidence interval, 2.39 to 2.88) relative to the female incidence rate. It was found that 71.8% of the dislocations were in males. Stratified by decade, the maximum incidence rate (47.8 [95% confidence interval, 41.0 to 54.5]) occurred in those between the ages of twenty and twenty-nine years; 46.8% of all dislocations were in patients between fifteen and twenty-nine years of age. There were no significant differences based on race. Dislocations most frequently resulted from a fall (58.8%) and occurred at home (47.7%) or at sites of sports or recreation (34.5%). Overall, 48.3% of injuries occurred during sports or recreation.
Conclusions: The estimated incidence rate of shoulder dislocations in the United States is 23.9 per 100,000 person-years, which is approximately twice the previously reported value. A young age and male sex are risk factors for shoulder dislocation in the United States population.