The prevalence of a large Hill-Sachs lesion that needs tobe treated

Background: A large Hill-Sachs lesion has been considered a risk factor for postoperative recurrence of shoulder instability. However, there are few reports describing the prevalence of Hill-Sachs lesions that engage with the glenoid. The purpose of this study was to clarify the prevalence of engaging Hill-Sachs lesions using the concept of the glenoid track. Materials and methods: The computed tomography images of 100 consecutive patients with unilateral recurrent anterior shoulder dislocations were assessed. An image in the plane perpendicular to the rotator cuff attachment was reconstructed from the DICOM (Digital Imaging and Communications in Medicine) data, and the maximum distance from the medial margin of the Hill-Sachs lesion to the medial margin of the rotator cuff footprint was measured. The location of the Hill-Sachs lesion in the glenoid track was assessed, and when the Hill-Sachs lesion extended medially over the glenoid track, it was defined as an "engaging Hill-Sachs lesion.". Results: Engaging Hill-Sachs lesions were observed in 7 of 100 cases (7%). There were 2 types of Hill-Sachslesions: a large and wide type (3 cases) and a narrow but medially located type (4 cases). All cases with an engaging Hill-Sachs lesion had a large bony defect of the glenoid at the same time. Conclusions: In our series of consecutive 100 cases, the prevalence of engaging Hill-Sachs lesions was 7%. There were 2 types of Hill-Sachs lesions: a wide and large type and a narrow but medially located type.