Epidemiology of primary shoulder dislocations requiring surgery: A cohort study from a major trauma center during 7 years.

Purpose: The epidemiology of shoulder instability in the general population is lacking. The aim of the current study was to determine the incidence rate of primary shoulder dislocations requiring surgical interventions in a major trauma center within a large maintenance organization.

Methods: A retrospective cohort analysis of electronic health records database from 1 January 2014 and 31 December 2020 was conducted in major rural trauma center. This study included all patients aged 10 years or older with a primary shoulder dislocation that were treated with closed reduction in the emergency room department. An overall incidence density rates (IDR) (per 100,000 person-years) of primary shoulder dislocations and stabilization surgeries were determined for the entire cohort. The data was used to evaluate the age-specific and gender-specific epidemiology.

Results: During the study period of 7 years there were 1,302 patients who underwent closed reduction after a primary shoulder dislocation (mean age 45 years). Of those, a total of 106 shoulder stabilization surgeries (8%) were performed. The IDR of primary shoulder dislocations was 179 per 100,000 person-years. The IDR of primary shoulder stabilizations was 15 per 100,000 person-years. The peak in number of dislocations was observed in the age groups of 20-29 years and over 60 years. In the age groups under 59 years dislocations were more common in men while in ages over 60 years dislocations were more common in women. The vast majority of shoulder stabilization surgeries were performed in young patients (age under 39 years).

Conclusion: The IDR of primary shoulder dislocations calculated from a major trauma center of the largest health maintenance organization in Israel was 179 per 100,000 person-years. Shoulder dislocations had bimodal age distribution. Overall, eight percent of the patients (mainly young) with shoulder dislocations underwent shoulder stabilization surgery during the study period.