Association between Baseline Demographics and Glenohumeral Joint Instability Injury- SOMOS 2025

m aderman, m donohue, s gee, m bradley, r robins, l leclere, r waltz, m slabaugh, t dekker, j dickens, k cameron

Abstracted accepted for a rapid-fire presentation at the 2025 Society of Military Orthopaedic Surgeons Annual Meeting.

INTRODUCTION: Active-duty military personnel and military service academy (MSA) cadets have demonstrated incidence rates of glenohumeral joint instability (GHJI) injuries approximately 20 times higher than the general population. These injuries can result in a diminished ability to meet the physical standards of the military which can ultimately lead to surgical intervention or medical separation. To decrease the incidence of GHJI injuries and mitigate the impact of these injuries on military readiness, identifying people at increased risk for sustaining a GHJI is critical. Therefore, the purpose of this study was to identify specific demographic and injury history factors associated with time to sustaining an incident GHJI injury during follow-up among MSA cadets.

METHODS: A prospective cohort study was conducted among cadets enrolled at a single United States MSA from August 2020 to August 2022. Demographic, health history, and sports participation information including sex (male, female), history of GHJI injuries (yes, no), history of surgery to correct GHJI (yes, no), current self-perceived GHJI instability in either shoulder (yes, no), and current participation in an overhead sport (yes, no) were collected at the time of consent upon accession. Participants were recruited to this study after their initial summer training during their first year at the MSA, prior to the start of the academic year. Injury surveillance was conducted among consented participants from enrollment until graduation or 16 May 2025. Any participants diagnosed with a glenohumeral dislocation or subluxation by an orthopedic surgeon, physical therapist, or athletic trainer was documented. The primary outcome of interest was time elapsed between enrollment in the study and an incident GHJI injury during follow-up. Kaplan-Meier survival estimates and univariate and multivariable Cox proportional hazards regression models were used to assess the association between both self-reported injury history and perceived joint stability and time to an incident GHJI injury while controlling for significant covariates. Descriptive statistics were calculated to quantify differences in time to injury by each covariate. Statistical significance was set at α<0.05.

RESULTS: During the study period, 1,326 participants (22% female; 18.89±1.63 y; 175.13±10.71 cm; 73.54±10.29 kg) agreed to participate in this study and 77 (26% female; 20.63±1.47 y; 174.37±10.27 cm; 75.10±11.62 kg) sustained an incident GHJI injury eligible for analysis. There were 32 dislocations and 45 subluxations diagnosed among the injured subjects. The mean time from baseline to GHJI injury was 462.88±362.77 days in participants who reported self-perceived instability at baseline, compared to 606.47±372.62 days among participants not endorsing perceptions of GHJI instability. Univariate Cox proportional hazards regression models revealed that participants reporting a history of GHJI (HR=6.370; 95% CI=3.83-10.60) and/or reporting current perceptions of GHJI in either shoulder (HR=6.085; 95% CI=3.13-11.87) at baseline were over 6 times more likely to sustain a GHJI injury during the follow-up period. Additionally, participants engaged in an overhead sport (HR=1.771; 95% CI=1.02-3.07) were 77% more likely to sustain a GHJI injury during follow-up than participants not participating in these activities. Sex (HR=1.232; 95% CI=0.74-2.05) and previous GHJI surgery (HR=0.907; 95% CI=0.28-2.89) reported at baseline were not associated with time to GHJI injury during follow-up. Kaplan-Meier survival estimates demonstrated similar results for each demographic and health history variable. Multivariable models controlling for sex and sport participation revealed that endorsing a history of GHJI (HR=6.409; 95% CI=3.79-10.83) and current self-reported perceptions of GHJI (HR=6.878; 95% CI=3.50-13.52) maintained a significant association with time to incident GHJI injury during the injury surveillance period.

DISCUSSION AND CONCLUSION: The endorsement of specific health history demographics upon accession to a MSA was associated with time to sustaining a GHJI injury during follow-up. Specifically, participants self-reported perception of GHJI and previous GHJI injury at baseline was associated with being over six times more likely to sustain an incident GHJI injury after accession. In addition to different patient-reported outcomes, demographics, and health history reported in previous research, self-reported instability in otherwise healthy MSA members may indicate they are at higher risk of sustaining a GHJI injury after accession.