Some different slides are down here, but I'll thank you. So we have no relevant disclosures. So our purpose of this study was to investigate the impact of the acromion process on the risk of surgical failure of posterior labral repair. In terms of known risk factors, we believe that the glenoid, specifically its retroversion as well as its associated bone loss may be associated with failure or with initial posterior shoulder instability. But even these risk factors are an area of ongoing research and current research is mixed. Acromion morphology has been linked to rotator cuff pathology, but its impact on shoulder stability has otherwise not been looked at significantly until recently. Professor Gerber and his group recently looked at the impact of the acromion on posterior shoulder instability and appropriately termed it as a Swiss chalet roof steep protective effect as demonstrated here, hypothesizing that it serves as a backstop or osseous restraint to posterior translation of the humeral head. Acromion morphology has also recently been associated with glenoid bone loss in posterior shoulder instability. And data out of the ANA meeting this year that's upcoming demonstrated that failed posterior instability not approved treatment was associated with differences in acromion morphology with greater posterior acromial height and less posterior acromial coverage. So in summary, it's been demonstrated that acromion morphology has been correlated with risk of initial posterior shoulder instability events, but there's no data yet on whether that correlates with surgical outcomes or revision rates. So with that in mind, we sought to investigate differences in scapular morphology in a series of primary patients who had successful posterior labral repair versus revisions, patients who failed their initial primary repair and went on to revision surgery. We hypothesized that failed patients would have more glenoid bone loss, more glenoid retroversion and acromion morphology differences, specifically with lower acromial tilt and higher posterior acromial heights. This was a retrospective review from 2005 to 2019 of active duty military patients who underwent posterior shoulder stabilization surgery. We collected basic demographics and looked at their preoperative pre-index surgery, MRIs to measure glenoid and scapular acromion morphology. We identified 41 successful primary posterior stabilization patients and 17 who failed their initial surgery and went on to revision. Unsurprisingly in the military, the group was predominantly male and the revision patients were significantly younger than that of the successes. To our surprise, there was no difference between the two groups, between glenoid bone loss both at 4.5% nor in glenoid retroversion both at 8 degrees. However, when looking at the acromial tilt, the successful patients had much higher tilts than those of the failures. Similarly with posterior acromial heights, successful initial primary surgeries had a lower posterior acromial height as shown on the left versus those who went on to revision had a higher posterior acromial height on the right there. Again there was no differences at least in our series between glenoid bone loss or glenoid version while there were significant differences between acromial tilts and posterior acromial heights between the success and failure groups. So in conclusion, in patients who had failure of their posterior stabilization surgery, their index acromial tilt was lower or flatter and their posterior acromial height was higher than in patients who had successful primary surgery. With this, this is consistent that the potentially high and flat at-risk acromial morphology puts patients at risk versus a more steep protective Swiss chalet roof. And then in our series at least, glenoid bone loss and version were not statistically different between these two populations. The immediate potential clinical impact of these findings that if you identify a patient with a high and flat acromion, you want to of course ensure robust soft tissue labor and repair. You may want to consider slowing the rehabilitation and counseling them on potential higher risk of failure of their soft tissue repair. And then supplemental techniques to minimize failure risk in these patients with high and flat acromion morphology may be justified. Thank you.

acromion process

surgical failure

posterior labral repair

shoulder instability

acromion morphology