Presentation
History of trauma two weeks ago, now presents with shoulder pain.
Patient Data
Axial nonarthrographic images clearly show anteroinferior labral injury with bony glenoid avulsion, a periosteal disruption, capsular injury, with free fluid tracking into the subscapularis muscle consistent with bony Bankart lesion. There is detachment of the labrum with mild anterior displacement of the labroligamentous complex. Fluid is seen to interpose between the detached osseous edge of anterior glenoid rim and the labro-osseous fragment. There is subjacent bone marrow oedema at the posterolateral humeral head which defines the Hill Sachs lesion. Some oedema is also noted at the posterior fibres of deltoid muscle, terminal pectoralis muscle and the coracoclavicular interval.
Coronal images show superior migration of the humeral head hence the incongruency at shoulder joint which contributes in the long run to instability and early rotator tendinosis.
Saggital images show widened anterior rotator cuff interval , which is distended with fluid, with poorly visualised middle glenohumeral ligament which is likely to be torn or damaged. Also seen is fraying and oedema at the anteroinferior labrum at site of injury
Case Discussion
Anteroinferior dislocation of the shoulder is the commonest type of shoulder dislocation, it involves injury to the anteroinferior glenoid margin with or without injury to the posterosuperior humeral head.
The fibrocartilaginous labrum lines the glenoid cup, deepening it and making the glenohumeral articulation more congruent and stable.
Injuries to the anteroinferior glenoid involve labral tear (soft Bankart) or bony injury, either a fracture fragment or microtrabecular injury (osseous Bankart). There is usually an associated area of subchondral marrow oedema at the humeral head with or without a depressed fracture. Needless to say that bone injuries are best assessed on CT.