Purpose: To characterize shoulder instability within the state of Rhode Island from 2011 to 2019.
Methods: The Rhode Island All-Payer Claims Database (APCD) was used to identify all patients that make an insurance claim related to a shoulder instability event. All patients in the APCD with an ICD-9 code of 718.31, 718.32, or 831.00 through 831.19 or an ICD-10 code of S43.001 through S43.086 or M24.41 through M25.319 between January 1, 2011 and December 31, 2019 were selected. Chi-square analysis was used to compare age- and sex-delimited subgroups; multivariate logistic regression was used to assess for factors influencing rates of surgical intervention and recurrent instability; and Kaplan-Meier failure and log-rank analyses was used to analyze variation in the time to surgery and recurrence between age-delimited subgroups.
Results: The incidence of overall shoulder instability (subluxations and dislocations) in Rhode Island was 62.20 instability events (95% CI, 60.61-63.78) per 100,000 person-years. The incidence of dislocations and subluxations were 49.46 injuries (95% CI, 48.05-50.88) and 12.73 injuries (95% CI, 12.02-13.45) per 100,000 person-years, respectively. Bivariate analysis demonstrated that male patients had significantly increased rates of surgical stabilization (6.36% vs. 2.80%) and recurrent instability (16.30% vs. 9.85%) compared to their female counterparts. However, after controlling for age at the primary instability event and the type and directionality of the instability, the difference in recurrence rates between males and females is no longer statistically significant (p = 0.326). Contrary to sex, age maintained its significance with those patients aged 20 and younger and 21-40 years at significantly increased odds of surgical stabilization (3.12 and 1.99, respectively) and experiencing a recurrent instability event (3.96 and 2.77, respectively).
Conclusion: These data characterize the epidemiology of shoulder instability within the state of Rhode Island and demonstrate how increasing age at a primary instability event decreases the likelihood of both surgical stabilization and rates of recurrence.
Keywords: epidemiology; glenohumeral instability; recurrent instability; shoulder instability; surgical stabilization.