Combined and Posterior Labral Tears are More Common in a Large Military Population with Operative Shoulder Instability than Previously Reported

OBJECTIVES: Shoulder instability is endemic in military and young athletic populations. Anterior shoulder instability is the most prevalent instability in civilian populations, but the unique physical demands placed upon military service members shoulders likely result in a different injury pattern. The purpose of the current investigation was to examine the distribution of labral tears across multiple military medical centers. We hypothesized there would be a higher incidence of posterior and combined labral tears treated operatively as compared to the civilian literature. METHODS: The Military Orthopaedics Tracking Injuries and Outcomes Network’s (MOTION) prospective Wounded Ill and Injured Registry (WIIR) was queried for all patients who had undergone a surgical stabilization procedure (CPT 29806, 23455, 23462) from October 2016 to January 2019. Patients with isolated superior labral repairs were excluded. Labral tear location was abstracted from intraoperative data collection forms. Chi-Square analyses (X2) compared the percentage of patients with isolated anterior, isolated posterior, isolated inferior, or combined labral tears between individuals in the current study cohort with a previously reported civilian Norway shoulder instability registry, a reported prevalence at the National Football League scouting combine, and with operative shoulder instability patients at a single military treatment facility. Chi-square analyses also compared differences in labral tear location between males and females. Statistical significance was set a priori at α ≤ 0.05. RESULTS: Three hundred fourteen patients (n=314) were identified who had undergone primary shoulder stabilization during the study period. Three patients were excluded due to insufficient data. Of the 311 remaining patients, 41 (13%) were female, 269 (87%) were male, 1 patient did not report a gender. All 311 patients’ military status was either active duty or active reserve (301 and 10, respectively). Ninety-four patients (30.23%) had isolated anterior labral tears (21 female, 73 male), 76 patients (24.44%) had isolated posterior labral tears (7 female, 69 male), 5 patients (1.61%) had isolated inferior tears, and 136 patients (43.73%) had combined labral tears. The number of posterior and combined labral tears in our data differed from previously reported percentages in the civilian literature (9.90% and 6.93%, respectively; X2(2)=208.94, p<0.00001). We also observed a higher percentage of combined tears than was previously reported from a military institution (18.61%; X2(2)=48.20, p<0.00001). The NFL combine cohort had 31% of players with anterior, 35% of players with posterior, and 35% with combined anterior/posterior labral tears (X2(2)=9.54, p=0.0085). Significantly more females (51.22%) had an isolated anterior labral tear, as compared to males (25.65%; X2(2)=9.25, p=0.009). CONCLUSION: The rate of posterior and combined labral tears in a military population with shoulder instability is higher than what is reported in the civilian literature, which is in keeping with a previous study at one Army medical treatment facility, although the rate of combined tears was even higher in the current cohort than previously reported in either population. The distribution of tear location is most similar tothat of an NFL combine population, supporting the thought that the military population should be thought of and treated as a population of athletes. Labral tears in females were more consistent with the civilian literature in that they had significantly more isolated anterior tears than posterior orcombined, which significantly differed from males. Military shoulder surgeons should be prepared to address multiple labral tears at the time of shoulder stabilization and be aware of the difference in tear location in females versus males.