Shifting paradigms: how the glenoid track changed the concept of shoulder instability

BACKGROUND : Historically, glenoid bone loss and humeral head defects (Hill-Sachs lesions) were evaluated independently. However, the clinical significance of a Hill-Sachs lesion depends on the morphology of the glenoid: an identical lesion may remain stable with an intact glenoid but become unstable in the presence of glenoid bone loss. Therefore, both lesions must be assessed simultaneously. LIMITATION OF TRADITIONAL ASSESSMENT: Traditional dynamic intraoperative examination has an inherent limitation. Engagement can be accurately assessed only after Bankart repair (post-repair examination), whereas remplissage, when required, must be performed before the repair (pre-repair examination). INTRODUCTION OF A NEW CONCEPT: To overcome this dilemma, the 'glenoid track' concept was introduced, enabling combined assessment of Hill-Sachs lesions and glenoid bone loss. Since its introduction, the concept has evolved through refinements such as consideration of subcritical glenoid bone loss, subdivision into central and peripheral tracks, and patient-specific adjustment of track width based on the range of motion. Efforts are also underway to establish accurate MRI-based assessment, facilitating widespread radiation-free application. EXTENSION OF THE CONCEPT: Furthermore, the concept has been extended to posterior shoulder instability through the development of the 'reverse glenoid track' concept, broadening its applicability across the spectrum of shoulder instability.