Incidental Findings of Shoulder Instability for Incoming Service Academy Members- SOMOS 2025
r Robins, h gibbs, m bradley, j dowe, l Leclere, r waltz, k cameron, m donohue, m slabaugh, t dekker, j dickens
Abstracted accepted for a rapid fire presentation at the 2025 Society of Military Orthopaedic Surgeons Annual Meeting.
US service academy members have a forty-times higher increased risk of sustaining a shoulder instability event during their time of enrollment compared to the general population. As a result, great efforts have been made to identify risk factors, mitigate injury occurrence, optimize treatment, and promote return to duty strategies for those enrolled at the service academies. A recent multi-center study effort recruited freshman at the US service academies to prospectively collect bilateral shoulder screening magnetic resonant imaging (MRI) studies. This cohort of service academy members allows the opportunity to understand the morphology of shoulders before instability events occur and compare this morphology to post-injury scans in members who experience shoulder instability events while at the service academies. This study also allows the opportunity to identify presence of pre-existing instability pathology in undiagnosed shoulders for matriculating freshman and compare to their contralateral uninjured side.
An IRB-approved longitudinal imaging study aimed at recruiting three consecutive years of incoming freshmen classes (graduating in 2024, 2025, and 2026) at the U.S. Air Force Academy, the U.S. Military Academy, and the U.S. Naval Academy were consented for voluntary participation to have both shoulders imaged with MRI early in their academic career. If an individual then sustained a shoulder instability event, the pre-injury screening MRI will be available for comparison to the post-injury MRI. Each class is currently being followed over their 4 years at the service academies and beyond into their active-duty military careers. In the collection of the screening MRIs, we identified individuals who entered the service academies with previous histories of shoulder instability pathology in one of their shoulders allowing for comparison to the opposite non-injured shoulder. All pre-existing shoulder injury MRIs were measured and evaluated for comparison to the opposite shoulder’s screening MRI. A paired sample t test was performed to compare morphological measurements within subjects.
77 individuals were identified with shoulder instability injury when completing screening MRIs of both shoulders. Of this number, 10 individuals had a history of bilateral instability, leaving 67 individuals identified as having shoulder instability pathology in one shoulder that was then available for comparison to their non-injured side. A total of 132 shoulder MRIs were measured and analyzed. Mean glenoid bone loss was significantly greater in injured shoulders compared to healthy shoulders (9.1% vs 6.2%, p<0.001). Injured shoulders also demonstrated significantly greater glenoid retroversion (8.2deg vs 1.5deg, p<0.001), and reduced posterior acromial tilt (36.2deg vs 53.1deg, p<0.001) relative to healthy shoulders. Hill Sachs Lesions (HSL) were present in 65 of 66 injured shoulders, with a mean lesion area of 0.7mm2. As of June 2025, 10 of these 67 pre-existing injured shoulders went on to have subsequent injury and shoulder stabilization surgery.
Shoulder instability events are common in young active individuals, and risk of instability is magnified when matriculating to a US service academy. We identified 77 freshmen who presented with pre-existing shoulder instability pathology on screening MRI, and 15% of those with unilateral injury went on to have subsequent shoulder instability events requiring stabilization surgery. In the injured shoulders, we identified a moderate rate of glenoid bone loss and glenoid retroversion, and a high rate of Hill-Sachs lesions on screening MRIs.