So the title of this presentation is Borderline Dysplasia. My name is Joshua Harris and I want to thank Anna for the invitation to present. I want to thank also Drs. Noe, Mather, and Larson, our co-chairs for the course. And here are my disclosures, none of which are relevant to this presentation. So borderline dysplasia is this controversial nebulous topic surrounding its terminology and definitions, and it falls along the stability spectrum and it's probably best termed transitional acetabular coverage, and it falls between normal coverage and dysplastic coverage associated with structural instability. For purposes of this talk, we'll use the definitions used in the literature for borderline dysplasia, which is primarily revolved around a single lateral center edge angle of 20 to 25 degrees. But dysplasia and borderline dysplasia are far more complex than just a single number and can include a variety of other measures. So one of the key points in evaluating this borderline group is it's not just a lateral center edge angle. There's a lot more to it than just a single measure of lateral coverage. And when you look at lateral coverage, there are two ways to define the lateral center edge angle, either to the lateral edge of the sore seal or to the lateral edge of the bone. We know when you look at the lateral edge of the sore seal, this is more of an anterolateral or an anterosuperior coverage. When you look at the lateral edge of the bone, it's more superolateral. So these are the most common radiographic ways to evaluate your lateral coverage. When looking at anterior coverage, the same concept applies. The anterior edge of the sore seal and the anterior edge of the bone. Now, these differences between lateral center edge of the sore seal versus the bone average about four degrees. But when looking at the anterior coverage, that difference can average as much as 10 degrees. So this has important implications for both diagnosis and treatment. For posterior coverage, retroversion can be radiographically observed with prominent ischial spine signs and posterior wall signs. Looking at acetabular inclination, the tonus angle is the most commonly used metric with a borderline definition of between 10 and 15 degrees. The fear index is a more recent measure of instability, and this also evaluates inclination. Patients with a higher fear index are going to be more unstable, and patients with a lower fear index are going to be more impingement. And if their LCEA is less than 25 and their fear index is also less than 5, there's an 80% chance that hip's stable and can be treated arthroscopically as more of an impingement hip rather than an instability hip. At the lateral margin of the acetabulum, an upsloping lateral sore seal is a good radiographic finding for hip instability, and it's seen in about 83% of patients with dysplasia and only a little more than half of patients with borderline. But if you take this a little bit further, the presence of the upsloping lateral sore seal is associated with an elevated BITEN score in more than half individuals with that upsloping lateral sore seal. So taking all of this primarily radiographic information together, the dysplasia location, or even the borderline dysplasia location, can be characterized with the Ottawa classification as either anterior, posterior, lateral, or global undercoverage. Don't forget the femoral side though. Watch the patient's gait as this can really clue you into their femoral version. And so the range of femoral version can be significant. If you look at a large surgical cohort, this range can be as much as 90 degrees. And so if you look at acetabular coverage and femoral version, this combination can help you evaluate the patient's risk for instability. And a simple three category classification presented recently by Dr. Kelly uses the femoral version, but also your lateral center edge and your alpha angles to try to distinguish patients with instability versus impingement. Lower numbers are more instability and higher numbers are impingement. So when patients present, they'll typically display more lateral or posterolateral pain than your nondysplastic impingement cases. They'll display signs of snapping, either internal from the iliopsoas, the snapping you can hear, or external from your IT band, the snapping you can see. They'll have abductor fatigue and apprehension. And on imaging, signs of increasing instability are going to be your hypertrophic labrum, seen more with classical dysplasia, in addition to a hypertrophic iliocapsularis and a thin patchless capsule. The easiest way to classify this, to dichotomize this, is if their story, their exam, and their images are pointing to instability, then PAO is probably your best choice, with or without a concurrent scope. If the story, exam, and images are pointing to impingement, do a scope. And remember, these patients can typically hurt for a long time, similar to that of impingement. Patients on average have symptoms for over five years and they see more than three doctors before they ever even get a diagnosis. And so if you have good indications, you can do a good job for your patients. The combination of their exam and their imaging are important. And we know that higher tonus angles and lateral center edge and anterior center edge angles probably need a PAO. In this recent multicenter study, if the tonus angle was more than 10 degrees, which is how borderlines defined in literature, and it's how we defined it for this presentation, 10 to 15, then there was an 84% chance of needing a second operation. And this has been found with other radiographic measures as well. More reoperations, the lower the lateral center edge and the anterior center edge go. So if you take patients to arthroscopy, keep your interportal small. When capsulotomies fail, they typically do at the interportal. Never make them more dysplastic, so don't trim more rim. You always want to preserve your labrum and that labral suction seal. Do not cut the iliopsoas, as this is an anterior stabilizer of your femoral head. And don't remove your ligamentum and always close or placate your capsule. So at the time of surgery, a good prognosis can be estimated with a type of articular cartilage lesion you may see. For an impingement hip, as you can see here, it's typically the outside end from the chondrolabral junction waving or delaminating down toward the fovea. And compare that to the dysplastic or borderline dysplastic, where more of an inside out lesion is commonly seen. So with properly selected patients and skillful surgical technique, you can do a great job for your patients. Five-year outcomes in separate cohorts can be equivalent to that of non-borderline patients, with both statistically significant and clinically meaningful improvements at this midterm follow-up. And so borderline dysplasia is a controversial topic, but it doesn't need to be. I think with clear terminology and definitions, you can achieve excellent outcomes for your patients, equivalent to that of a normal coverage group, as long as you pay close attention to both the bony structural details and the soft tissue contributions with an arthroscopy. And if they're more than that, if they're more than borderline with true structural instability, do a PAL. Thank you.

Borderline Dysplasia

Radiographic evaluation

Instability

Treatment decisions

Surgical options