to present our research. We have no disclosures. Radiographic diagnoses in hip preservation surgery are essential for a number of reasons. First, they can determine the diagnosis, whether that's dysplasia or femoral acetabular impingement. Radiographic measurements can also identify patients who have both diagnoses of impingement and dysplasia, for example, and these diagnoses dictate our treatment plan for the patient. Having good radiographs can also establish consistency with pre- and post-operative evaluation, as well as intraoperative evaluation of the hip joint. Prior research has shown us that standing AP pelvic radiographs have decreased pelvic tilt when compared to supine radiographs, and this decreased pelvic tilt results in a lower incidence of pincer-type diagnoses found on radiographic imaging. Prior cadaveric studies have shown us that pelvic tilt also alters the measure of lateral center edge angle, crossover sign, and tonus angle, and then prior CT studies have shown us that changes in pelvic tilt will influence the functional orientation of the acetabulum. So currently, there are a large number of radiographic measurements that we use on AP pelvic radiographs. However, there's no current standardization amongst hip arthroscopists or hip preservation surgeons on whether we obtain these radiographs in the standing or supine position. So we sought to determine differences in radiographic measurements between supine and standing radiographs in the same patient in our hip preservation population. All new patients who presented to a single surgeon's clinic between the fall of 2017 and fall of 2018 were retrospectively reviewed. Those who had pelvic radiographs both standing and supine dated within two years of one another, and otherwise met our inclusion criteria were included in the study. And measurements were ultimately obtained on 52 hips with the surgeon making the measurements blinded to patient demographics and whether that film was obtained in a supine versus standing projection. Measurements obtained included the minimum joint space, lateral center edge angle, acetabular depth, acetabular inclination, tonus grade, crossover sign, whether it was present or absent, the posterior wall sign, and the ischial spine sign. So here's an example of a patient who presented with a supine pelvis radiograph positive for ischial spine sign and positive for bilateral crossover signs. On repeat standing radiograph you can see that these findings disappeared. This is another patient who presented with a supine pelvic radiograph with positive bilateral posterior wall signs, and on standing radiographs these signs disappeared. As we know the ideal AP pelvis radiograph is described as having the coccyx centered above the pubic symphysis and approximately one to three centimeters above that pubic symphysis with symmetric obturator foramen. We found that in patients who had supine pelvic radiographs that were acceptable based on those descriptions, findings such as bilateral crossover signs still disappeared when you got a standing x-ray. We found that standing radiographs resulted in a significantly lower lateral center edge angle, lower acetabular depth measurements, and a higher acetabular inclination measurement. Supine radiographs were significantly more likely to have a positive crossover sign and positive ischial spine sign. So in conclusion, supine AP pelvis radiographs are six times more likely to give a positive crossover sign and eight times more likely to give it a positive ischial spine sign than standing radiographs in that same patient. And standing AP pelvis films will result in a significantly lower lateral center edge angle measurement, lower acetabular depth measurements, and a higher acetabular inclination. So based on these results our recommendation is to obtain AP standing pelvis radiographs on all hip preservation patients. Thank you.

radiographic diagnoses

hip preservation surgery

dysplasia

femoral acetabular impingement

standing pelvis radiographs