Recurrent Anterior Shoulder Instability with Inferior Glenoid Fracture Leading to Mechanical Subacromial Impingement: Imaging Considerations and Diagnostic Algorithm
Ayten Akhundova
Ayten Akhundova
Scientific Surgery Center named after Academician M. Topchubashov, and the Central Clinical Hospital, Baku, Azerbaijan.
Background: Traumatic anterior shoulder instability is frequently associated with osseous defects of the
glenoid and humeral head, which significantly influence recurrence risk and surgical decision-making.
Beyond instability, structural bone loss may also contribute to secondary mechanical subacromial
impingement through altered glenohumeral biomechanics and superior humeral migration. The
coexistence of glenoid fracture and secondary post-traumatic impingement represents an underreported
clinical scenario, and an evidence-informed imaging strategy for this combined pathology has yet to be
clearly established.
Objective: To explore the complementary diagnostic utility of MRI and CT in a clinically
undercharacterized scenario - post-traumatic shoulder impingement secondary to inferior glenoid
fracture in recurrent anterior instability.
Case Presentation: A 41-year-old physically active male presented with persistent shoulder pain two
weeks following a traumatic episode on a background of recurrent anterior dislocations. The pain
intensified at night and during arm elevation above 90° and posterior movements, raising clinical
suspicion of subacromial impingement.
Methods: Initial evaluation with MRI revealed a post-traumatic fracture of the inferior glenoid rim
with partial displacement, narrowing of the glenohumeral joint space, partial superior migration of the
humeral head, reduced acromiohumeral distance, supraspinatus tendinopathy with partial-thickness
tearing and bone marrow edema, as well as subacromial bursitis and rotator cuff edema. Subsequent CT
imaging was performed to refine osseous assessment and demonstrated detailed fracture morphology,
articular surface deformation, displacement extent, and associated cystic osteodegenerative changes of
the humeral head.
Results: Imaging findings supported a sequential pathomechanism: glenoid bone defect → increased
instability → superior humeral migration → subacromial narrowing → supraspinatus compression and
degeneration. MRI proved superior for detecting soft tissue pathology and marrow edema, whereas CT
provided high-resolution characterization of fracture configuration and articular involvement, critical
for therapeutic planning.
Conclusion: In post-traumatic shoulder impingement associated with glenoid fracture and recurrent
instability, reliance on a single imaging modality may result in incomplete structural assessment. MRI
and CT serve complementary roles: MRI excels in evaluating soft tissue and inflammatory components,
while CT remains indispensable for precise osseous mapping and assessment of articular surface
displacement. A staged, multimodal imaging approach enhances diagnostic accuracy and supports
informed management decisions.
