I'm Jamie Friedman from the University of Connecticut. I have no disclosures. The senior author has the following disclosures. With both glenoid and humeral head defects, there may be increased shoulder instability, but more importantly, there's a higher risk of fixation failure. The glenoid tract concept came into play several years ago as a way for us to objectively measure these two lesions as one bipolar lesion, which we now refer to as on and off track. Thinking of the bipolar lesions together is so important because we've found that the amount of critical glenoid bone loss may be much less than we initially thought when there's a concomitant Hillsex lesion. We predicted that an off track lesion measured by advanced imaging would correlate with a three plus load and shift exam under anesthesia. This was a retrospective study using three CPT codes with two surgeons over approximately two years. We collected the patient's demographic data and surgical information. We got their exam under anesthesia from the operative report while we used advanced imaging measured by two independent researchers that were not involved in the patient's care to allocate them to on or off track. Many disagreements between the researchers were settled by a fellowship trained MSK radiologist and we calculated the inter observer reliability. I'd just like to highlight, as you know, that a true three plus on the load and shift exam does require manual reduction as the humeral head locks out over the glenoid rim. So here's an example of an EUA with a three plus translation of a right shoulder requiring manual reduction. This is what we hypothesized would correlate to an off track lesion on advanced imaging. You can see it goes in right there. So sagittal and axial images of a CT or MRI were used to measure the glenoid track, excuse me, the glenoid and humeral head respectively. As demonstrated on this 3D reconstruction, we first measure the glenoid track and then subtract the glenoid bone loss and on the humeral side, we add the Hill Sachs lesion and the bony bridge to create the Hill Sachs index and then these two values are compared to each other to determine whether the lesion is on or off track. Of the 89 eligible patients for further review, we had approximately 70 percent males with an average age of 29 years. First we measured their advanced imaging and then we correlated this with their exam under anesthesia from the operative report. As you can see, 90 percent of the on track lesions did not lock out on an EUA and the majority, about 64 percent of the off track lesions did have a three plus EUA. So overall the glenoid track measurements on advanced imaging correlated with the exam under anesthesia 83 percent of the time. Our high specificity and negative predictive value indicate a low likelihood of an on track lesion having a three plus load and shift exam. Even though our positive predictive value seems low, it is still significantly higher than other studies that use a greater than 20 percent glenoid bone loss to predict an engaging lesion. There are also studies that question the reliability of the glenoid track measurements. However, our study did show excellent inter-observer reliability between the two independent researchers. There were five cases of disagreement between the researchers which were settled by a blinded MSK radiologist and our kappa statistic was 0.83. So overall we had both glenoid track measurements and an exam under anesthesia that were consistent within our study. But it is important to note that this is a retrospective study and it is also important to note that the majority of our patients come from a tertiary care center where we treat a wide variety of complex patients that are referred to us with possible previous failures and outside imaging. In conclusion we found a high correlation between the imaging and the exam under anesthesia in our study. But going forward the important thing that we're trying to find is how we review all of these patients' outcomes and correlate how they did on the outcomes to their preoperative imaging, the exam under anesthesia, and what type of surgical procedure they actually underwent. Thank you.

glenoid track

shoulder instability

off track lesions

advanced imaging

load and shift exam