AJSM Webinar Series: Posterior Shoulder Instability: Understanding the Dark Side of the Shoulder-A New Concept of Reverse Glenoid Track to Determine Which Reverse Hill-Sachs Lesion Should Be Treated

A New Concept of Reverse Glenoid Track to Determine Which Reverse Hill-Sachs Lesion Should Be Treated

Pdf Summary

This study by Ishizu et al. introduces the "reverse glenoid track" concept to guide the surgical treatment of reverse Hill-Sachs lesions resulting from posterior shoulder dislocations. While the glenoid track concept is established for anterior dislocations—where the risk of lesion engagement depends on lesion location relative to a contact zone—the surgical indications for reverse Hill-Sachs lesions have been unclear.<br /><br />The researchers examined 20 shoulders from healthy volunteers using 3D MRI scans at three degrees of arm flexion (0°, 45°, 90°) with maximal internal rotation and horizontal flexion. They reconstructed 3D bone models and measured the contact areas between the humeral head and glenoid, revealing that as flexion increases, the glenoid contact area shifts along the lesser tuberosity from inferomedial to superolateral regions on the humeral head, creating a defined contact zone, termed the "reverse glenoid track."<br /><br />Key findings include that the reverse glenoid track width measured from the articular cartilage margin ranged from 50% to 59% of the glenoid width, while measurements from the rotator cuff footprint margin ranged 80% to 92%. Measurement reliability was higher using the cartilage margin. The study suggests a reverse Hill-Sachs lesion that extends medially beyond this reverse glenoid track risks engagement with the glenoid rim and thus warrants surgical treatment. Conversely, lesions contained within the track pose less risk and may not require surgery.<br /><br />The authors discuss that bone grafting procedures effectively treat off-track lesions by medializing the glenoid track to encompass the defect, preventing engagement. Limitations include small sample size, MRI resolution constraints, and measurement at only three flexion angles up to 90°. The study recommends using 3D CT imaging for more precise clinical assessment.<br /><br />In summary, this pioneering reverse glenoid track concept, analogous to the anterior glenoid track, provides a biomechanical basis for deciding which reverse Hill-Sachs lesions in posterior shoulder dislocations require surgical intervention, enhancing clinical decision-making and patient management.

Keywords

reverse glenoid track

reverse Hill-Sachs lesion

posterior shoulder dislocation

3D MRI shoulder imaging

humeral head contact area

surgical treatment indications

glenoid track concept

bone grafting procedures

lesion engagement risk

shoulder biomechanics