Incidence and Characteristics of Traumatic Shoulder Instability in Japanese Military Cadets

Abstract

Little is known regarding the incidence of the shoulder instability in Japan. The aim of this study was to evaluate the incidence of traumatic shoulder instability among Japanese military cadets. A prospective cohort study was performed to capture all traumatic shoulder instability events between 2009 and 2012 among cadets in a military educational academy of the Japan Self Defense Forces. The total number of cadets in the cohort was 5,402 (average age 20.6 years). The incidence of instability events, including dislocation or subluxation, was calculated. Chronicity, demographics of participants, mechanism of injury, and athletic events were also evaluated. The incidence of traumatic dislocation was 4.1/1,000 person-years and that of subluxation was 6.1/1,000 person-years. The incidence of primary dislocation or subluxation was 5.4/1,000 person-years and that of recurrent dislocation or subluxation was 4.7/1,000 person-years. Of first dislocations or subluxations, 92% occurred during sports activities, including after-school sports activities, military training, and gym classes. In conclusion, the overall incidence of shoulder instability events among Japanese military cadets was 10.3/1,000 person-years, and was extremely high. Most shoulder instability events occurred during sports activities, and a program to prevent such injuries during sports activities is necessary for young participants.

Translation and validation of a Hebrew version of the Western Ontario Shoulder Instability index

“…Anterior shoulder dislocations are the primary cause of shoulder instability (SI), a condition that refers to the inability to maintain the humeral head in the glenoid fossa [1]. The incidence of primary shoulder dislocation is 8.2 to 23.9 per 100,000 person-years, and its estimated prevalence is 1.7% [2, 3]. About two thirds of shoulder dislocations will evolve into SI within five years [4].…”

Incidence and Risk Factors of Upper Extremity Injuries in Young Adult Men: A Nationwide Registry-Based Study of 128,714 Conscripts

“…In other studies with military populations, the incidence of shoulder joint dislocations is reported to be even higher. [28][29][30] Amako et al 29 reported an incidence of 410 per 100,000 person years among Japanese military cadets, Kardouni et al 30 reported an incidence of 313 per 100,000 person years among U.S. military soldiers, and Owens et al 28 reported an incidence of shoulder joint dislocation as high as 435 per 100,000 person years among U.S. military cadets.…”

The supine moving apprehension test—Reliability and validity among healthy individuals and patients with anterior shoulder instability

“…Shoulder dislocation often occurs during high-intensity athletic activities. 9 , 10 The majority of dislocations are anterior and typically occur when sudden forces at the extreme ends of glenohumeral abduction-external rotation are adequate to displace the humeral head anteriorly. 11 The anterior shoulder musculature, namely the pectoralis major, anterior deltoid, biceps brachii, coracobrachialis, and subscapularis are considered dynamic anterior stabilizers of the shoulder and therefore most suited to protect it from anterior dislocation.…”