Thank you, and thank you to my co-authors as well. We have no disclosures related to this study. The study was recently published in the March issue of the Journal of Arthroscopy if you want to learn more about it. So in patients with acetabular dysplasia, hip instability leads to chronic shear stress between the femoral head and the acetabular roof, leading to compensational labral hypertrophy in order to maintain the femoral head within the joint. And we know of multiple studies that have confirmed an inverse relationship between the degree of acetabular boning coverage and the size of the acetabular labrum. We all know what the lateral center edge angle is, and in this study we've defined a modified measurement of lateral coverage that includes the osseolabral structures measured on MRI. And we've defined this new parameter, the combined lateral center edge angle. The purpose of this study was to compare the combined lateral center edge angle between groups of patients with varying degrees of acetabular boning coverage, and we hypothesized that the labral hypertrophy that occurs in patients with acetabular dysplasia will compensate for the lack of bony coverage such that the combined lateral osseolabral coverage remains normal across patients. This was a retrospective observational cohort study with the lateral center edge angle determined on AP radiographs, and all patients were divided into four different groups based upon the degree of acetabular boning coverage, with borderline dysplasia defined by a center edge angle between 20 and 25 degrees, and frank hip dysplasia defined by a center edge angle under 20 degrees. The combined lateral center edge angle was measured on three Tesla MRI in all patients, and it was defined as the angle subtended by a line through the center of the femoral head and perpendicular to the teardrop line, and another line drawn from the center of the femoral head to the free edge of the lateral acetabular labrum. Finally, we performed a linear regression model in order to obtain predicted combined lateral center edge angle values based upon the lateral center edge angle. So to show an example of this, in figures A and B, we had the same patient with a normal degree of acetabular boning coverage and a center edge angle of 30 degrees, and you can see that when we measure the combined lateral center edge angle on MRI, this patient has a combined center edge angle of 45 degrees. Then in figures C and D, we have a patient with acetabular dysplasia and a center edge angle of only 16 degrees, but because the labral hypertrophy that's occurred in this patient, this patient has a combined center edge angle of 43 degrees, almost equivalent to that patient in figures A and B. So overall, 341 patients in 386 HIPs were included with a mean age of 33 years and a good distribution of patients based upon the degree of acetabular boning coverage. When we look at HIPs divided into groups based upon the degree of acetabular boning coverage, there were significant differences between the center edge angle and the combined center edge angle in all groups. However, when we look at the combined center edge angle values circled here in red, we can see no significant differences between patients with normal bony coverage and HIP dysplasia or borderline dysplasia. Also, if you just look at the absolute values of the combined center edge angle, you can see that there's a very narrow range between the different groups, with only eight degrees difference between patients with dysplasia and acetabular overcoverage. To further emphasize this, here are the results of our linear regression analysis, and again, when looking at such a wide range of patients based upon the center edge angle, going from zero to 43 degrees, still there's very narrow range of combined center edge angle values, with only a six degree difference from 42 degrees to 48 degrees. So in conclusion, with decreasing acetabular bony coverage, there's increasing labral size such that the total osseolabral coverage measured by the combined center edge angle value remains clinically unchanged, and HIPs with acetabular dysplasia exhibit equivalent lateral osseolabral coverage when compared with normal HIPs. Thank you.

acetabular dysplasia

hip instability

labral hypertrophy

lateral center edge angle

labral coverage