Does glenoid bone loss accompany posterior shoulder instability with only labral tear? A magnetic resonance imaging-based study.

BACKGROUND

The primary aim of this study was to investigate bone loss in the glenoid with magnetic resonance imaging in posterior shoulder instability with only a labral tear.

METHODS

A total of 76 patients operated on because of posterior and anteroposterior shoulder instability only with a labral tear between 2006 and 2019 (n = 40 and n = 36, respectively) were included in this study. The instability type, a presence of an additional superior labrum anteroposterior (SLAP) lesion, the number of dislocations, and the magnetic resonance imaging-based measurements (the glenoid diameter and the bone defect size in the glenoid, the Hill-Sachs lesion [HSL] and the reverse HSL [rHSL] length, the angle and the arc length of HSL and rHSL, and the humerus head diameter and its area) were analyzed.

RESULTS

The size of the anterior glenoid defect, the rHSL measurements (length, angle, and arc length), and the ratio of the anterior glenoid defect size to the glenoid diameter were significantly higher for anteroposterior instability (P < .01) cases. There was no significant difference (P = .49, .64, and .82, respectively) for the presence of an additional SLAP pathology, the glenoid diameter, the posterior glenoid defect, and the ratio of the posterior glenoid defect size to the glenoid diameter in posterior and anteroposterior instability groups. The increased number of dislocations was associated with increased rHSL length and total arc length (P = .04 and .03, respectively). An additional SLAP lesion in posterior shoulder instabilities was not associated with the bone defect size (P = .29).

CONCLUSION

Although the posterior shoulder instability with only a labral tear is likely to cause a bone defect, we have shown that the instability is not expected to be caused by the bone defect. Therefore, this study points out that only soft tissue repair without considering the bone defect could be promising in this patient group.