Shoulder Dislocation 10-year Incidence And Chronic Injury Rate In The U.s. Army

Abstract

Active duty United States (US) Army soldiers represent a relatively young, active cohort of the US general population. Musculoskeletal injury is a leading cause of disability in the US Army. However, the recent rate and risk factors for shoulder dislocations in the US Army have not been determined. PURPOSE: Determine the 10-year incident rate of shoulder dislocations in the US Army, the percentage with recurrent instability, and demographic groups at risk for these injuries. METHODS: Medical encounter data for US Army soldiers was used to quantify shoulder dislocations from 2002-2011 using ICD-9 diagnosis codes. Ten-year incidence rate for shoulder dislocations was calculated, as was the percentage of chronic or recurrent injuries >3 months and ≤2 years following the initial diagnosis. A conditional logistic regression was performed using demographic variables (age, race, military career field, education level, marital status, and sex) to determine risk ratios (RR) for risk factors related to shoulder dislocation. A logistic regression was performed to calculate RR for risk factors for recurrent injury including concurrent diagnoses (brachial plexus or peripheral nerve injuries, fractures of the scapula or humerus). RESULTS: There were 15,471 incident shoulder dislocations, with a 10-year incidence rate of 3.10 per 1,000 person years. Compared to soldiers >40 years old, soldiers ≤30 years old had greater risk of injury (<20 years RR=2.35, 95% CI [2.10, 2.633], 21-25 years RR=2.14, 95% CI [1.94, 2.35], 26-30 years RR=1.71, 95% CI [1.55, 1.87]). The RR for males compared to females was 1.97, 95% CI [1.85, 2.09]. Recurrent injury occurred in 32.1% of cases. Concurrent peripheral nerve injury (RR=1.93, 95% CI [1.14, 3.29]) and age ≤30 years (<20 years RR=1.91 95% CI [1.51, 2.4], 21-25 years RR=1.93 95% CI [1.57, 2.36], 26-30 years RR=1.63, 95% CI [1.33, 2.00]) had greatest risk of recurrence. CONCLUSION: Within the active duty US Army, men and those 30 years of age or younger showed greater risk for shoulder dislocations. Roughly one third of incident cases became recurrent. Peripheral nerve injuries and younger age increased the risk of recurrent injury. The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.