Dr. Justin Arner:               Welcome to Arthroscopy Association's Arthroscopy Journal Podcast. The views expressed in this podcast do not necessarily represent the views of the Arthroscopy Association or the Arthroscopy Journal. Welcome, everyone, I'm Dr. Justin Arner from the Steadman Clinic and Steadman Philippon Research Institute in Vail, Colorado.

                                                Today, I have the distinct privilege of speaking with one of my mentors and someone who needs no introduction, Dr. Marc Philippon, hip surgeon, fellowship director, and managing partner at the Steadman Clinic and chief medical officer of the Steadman Philippon Research Institute in Vail, Colorado.

                                                Dr. Philippon was the author of the paper entitled, “Predicting Severe Cartilage Damage In The Hip: A Model Using Patient-specific Data From 2,396 Hip Arthroscopies,” which is published in the July 2019 issue of the Arthroscopy Journal. Welcome, Dr. Philippon, and thank you for joining me.

Dr. Marc Philippon:         Well, thank you, Justin, for putting this together. I'm honored to be part of this podcast. Again, thank you very much for asking me to be part of it.

Dr. Justin Arner:               Thank you. Let's get right to it. What was your inspiration behind evaluating almost 2,500 patients to create this incredible cartilage predictive model?

Dr. Marc Philippon:         Well, you're right. This is a unique and powerful study evaluating the cartilage damage on the acetabulum and femoral head in young and active FAI patient without arthritis on x-ray. Really the idea came from notes we were taking in all our patient and the specific numbers I've used for many years, going back to when I was in Pittsburgh, actually. I like to have certain measurements in front of me when I do the surgery.

                                                A couple of years ago I had a very smart young man, a fellow from Japan. His name was Dr. Hajime Utsunomiya and also known as Jimmy. He noticed that with every single patient we had that little yellow note with numbers on it and we had a discussion. He asked me, he said, "Dr. Philippon, why are you using this?" I said, "Well, I like to know these measurements so I know what kind of cartilage damage we'll have in the hip before we start and just to be prepared." Based on this, we decided to do that study and work on this algorithm to predict severe cartilage damage in the hip.

Dr. Justin Arner:               That's really a unique and powerful study with a whole large number of patients. One thing I have found interesting that on arthroscopy, 41% of the hips had severe cartilage damage on the acetabulum, but 11% had severe lesions on the femoral head. Why do you think that is, especially when you excluded Tönnis 2 or 3 patients?

Dr. Marc Philippon:         Well, that's a good question. As you know, most of our hip arthroscopies involve treating the conflict from femoroacetabular impingement and, as you know, most of our patient have mixed-type impingement. We know what that with the mixed type of impingement, especially with the cam type, the stress really is at the chondrolabral junction.

                                                When you split that chondrolabral junction, there's a carpet delamination that starts at the acetabular chondral surface. I would say in most of our patient, if not all our patient, that junction is disrupted and, in my experience, that's the beginning of the chondral degeneration. It's really start on the acetabular side. Then of course, eventually depending on the stage of the patient we treat, the length of their symptoms, we'll see reciprocal changes on the femoral head.

                                                Now, as you know, we don't treat a lot of dysplastic patient because we refer them for PAO, or we do combined procedures. But the borderline dysplastic patient, we feel the mechanism of chondral damage is a little different. In our practice, we treat obviously FAI, borderline dysplastic traumatic injury, but truly we feel that the damage on the cartilage most of the time start on the acetabular side and that model proves that.

Dr. Justin Arner:               Yeah, it adds up with certainly your findings. I know there's been a few studies that show even 3T MRI has limited sensitivity in identifying chondral lesions of the hip. Why do you think that is? Do you find the femur or the acetabulum are easier to identify cartilage lesions?

Dr. Marc Philippon:         Well, 3T MRI is a big improvement from the 1.5, but I still feel it's very difficult to see chondral damage on the MRI. I feel it's easier on the acetabular side because I'm used to looking at the chondrolabral junction and, in my experience, it's been easier to determine precisely the damage to the cartilage on acetabular side versus the femoral head.

                                                Now subchondral edema is helpful also to evaluate as that leads us to the location of the cartilage damage. But I feel when we do our MRI on the hip, the patient is supine and, as you know, the hip joint is very congruent. So if there is no big joint effusion, sometime it's really difficult to see the displacement of the labrum and, therefore, seeing that chondral damage because the labrum is being reduced by the femoral head pushing against the acetabulum.

Dr. Justin Arner:               That makes sense. Before you started this study, did you have any factors that you thought might predict severe cartilage damage?

Dr. Marc Philippon:         Yes. As a matter of fact, I would refer to a paper we wrote with Dr. Johnston a few years back published in the Arthroscopy Journal, where we define the hip at risk. What we found in that paper was that the larger the alpha angle, the more damage we had to the acetabulum. So one of our hypothesis was that the larger the cam, the alpha, more damage we would see on the cartilage.

                                                Also, of course, the center edge angle is important, but also the Sharp angle. I know the Sir John Charnley used to use a Sharp angle for his dysplastic patient as probably a more predictable indices for assessing the shallowness of the acetabulum. Actually Dr. John Feagan, God bless him, he recently passed, but Dr. John Feagan wrote this paper on dysplasia of the hip with Sir John Charnley and he brought to the attention the importance of the Sharp's angle. So we felt that Sharp's angle will be an important measurement.

                                                Also the length of the symptoms is important. Also what I find important was that the actual motion at risk, understanding the activity at risk, ice hockey, American football, European football, soccer, baseball, golfers, these motion are different with subtleties. I feel that understanding the motion at risk really helps predict the repetition of the conflict and also helps us understand where the chondral stress or damage will be.

Dr. Justin Arner:               Since you brought that up, I was curious also how you counsel those patients with hips at risk, say for timing-wise, if they want to delay surgery for a more convenient time. I know you mentioned the longer period of symptom onset to surgery could be a risk factor as well.

Dr. Marc Philippon:         Yeah, that's a very good question and we looked at that, Justin. We reviewed 28 NHL hockey players that we treated with arthroscopic hip surgery for FAI and we published that in the peer-reviewed literature. We found in that group of professional hockey players that the longer they had their symptoms, the more chondral damage we saw at the time of surgery. But also we saw in analyzing the result, we found that these patient took longer to rehab. So the length of the symptoms, we feel, is also a predictor of chondral damage.

Dr. Justin Arner:               Just to summarize for the listeners, the findings of your study, the femoral head lesions were associated with lateral center edge angle and Tonnis angle while the acetabular lesions were associated with alpha angle, as you mentioned, males and higher BMI, as well as joint space and both lesions were associated with age. Do you have any thoughts about how you think through these things with factors that affect the acetabulum versus the femoral head and male patients being more susceptible?

Dr. Marc Philippon:         Yes. Yeah, I think it's important to understand that if I have a patient coming in with symptoms, who is a young 20-year-old ice hockey player, I will probably be more aggressive as far as intervention, surgical intervention, versus a 17-year-old pincer base impingement who is a ballerina. I think we have more room on these patient to wait with conservative treatment versus these young male or female with large cam who are involved with sports at risk. I think these factors, borderline dysplastic or dysplastic versus mixed type or large cam impingement, really helps us guide our clinical decision-making as far as intervention.

                                                As you know, it's always better a trial of conservative therapy, but if you have a patient coming in who was symptomatic for a year, sports at risk, certainly put the hip at risk as far as chondral damage. From what I've learned and we've all learned over the years, the more advanced the chondral damage, the more risk we will have to have a good outcome. Unfortunately, arthritis or more advanced chondral damage often correlates with a suboptimal outcome after a surgical intervention.

Dr. Justin Arner:               So would you say then the borderline dysplastic patient with a less risky sport profile you might be more willing to wait because likely their cartilage injuries maybe aren't as severe?

Dr. Marc Philippon:         Yeah. Borderline dysplastic, but there's no cam and their symptoms are coming from the borderline dysplasia.

                                                When I talk about borderline dysplasia, I'm thinking about 20 to 25 degrees of center edge angle, those patient I'll be less aggressive. But often though, unfortunately, these patient have large labrum with detachment, so definitely the labrum is pain generator, the chondrolabral junction is a pain generator. But those patients we'll be probably less aggressive as far as timing on intervention, because we don't have to deal with a large cam in most of them.

Dr. Justin Arner:               I noticed in this study you excluded patients less than 16 years old. Will you talk about, are you a little less aggressive in those skeletally immature patients? If they don't have a big cam, is it kind of the same procedure?

Dr. Marc Philippon:         Yeah. I really feel that during adolescence when we have skeletal immaturity, there's a lot of physiological changes that are happening, bone growth, muscular lengthening adjustment from the bone growth, lot of dynamics. I feel in that group of patient, 11 to 16, if we can avoid an intervention and wait until they have skeletal maturity, it will lead most of the time with better outcome.

                                                We publish also in Arthroscopy few years back looking at patient in the age group from 11 to 16 and we find in that age group, especially the female group, a higher rate of revisions due to often adhesions as high as close to a little over 9% versus males. So we feel that that age group often, if they don't have the combination of sports at risk and large cam, often we will try to wait for the surgical intervention until they reach skeletal maturity.

                                                Having said that, sometime in some sports we cannot wait because the labrum is flipped in and we have to repair it so we have to address the pain generator. So we operate on these patients, but again, we try to exhaust all conservative measures before we intervene.

Dr. Justin Arner:               Yeah. I thought about the labrum flipping in as another segue to another thought I had was I know there are some economic analyses, like Cunningham's, that have shown that exam and x-ray are commonly enough to diagnose FAI. Do you think models like this have the potential to replace preoperative MRI since maybe they're not as accurate for cartilage? Or what are your thoughts regarding those studies?

Dr. Marc Philippon:         Well, that's a very good and timely question. The reason why we did that model also is we felt that by good x-ray measurements, we can predict with high accuracy where the chondral damage will be. In certain part of the country or part of the world, MRI are not as easily accessible as we have in the US here in specialized clinic so we felt that having the ability to optimize all the information we can get from x-rays was very important. For sure, an MRI is very important because we can see more details about the bone marrow and periarticular musculature, tendonitis, all that and joint effusion. But I feel that having good x-ray series, you can gather a lot of very important information and guide your surgical intervention plan very, very precisely.

                                                Then, of course, having the luxury of getting MRIs, especially in 2020, it's easier to get MRIs, but I really think can get all that information from your x-rays. I wouldn't say it would replace the MRI, but in certain situation, if that's all you have, you can have a good prediction in combination with your physical exam, a good idea of what you're going to find at the time of surgery and be prepared for the intervention, be better prepared.

Dr. Justin Arner:               Do you see a role for three-dimensional imaging, such as 3D CT, or hopefully in the future, maybe 3D MRI to better define the cam or pincer lesion or aversion of the acetabulum or femur?

Dr. Marc Philippon:         Yes. I really like three-dimensional studies because, as you know, biplanar studies to treat a three-dimensional problem is more challenging.

                                                But I feel that in the future we'll have access to 3T MRI and then it will help us really assess more precisely the conflict, especially understanding the acetabular retroversion or pincer issue in the cam in combination. I feel it's very important to take into consideration not only the alpha angle, but also your acetabular pathology, because I see the femoroacetabular impingement syndrome as a couple, couple between the femoral side and the acetabular side. So I think it's important to take both into consideration and, certainly, the 3D analysis from CT or MRI is certainly a very important adjunct to our preop planning.

Dr. Justin Arner:               Yeah, 3D MRI would really add a lot, I think, without having to get another scan and I think we're getting closer. Could you tell us a little bit about how you treat focal cartilage lesions in 2020 and a little bit about microfracture and how you use different cartilage procedures in your practice?

Dr. Marc Philippon:         Yep. Most of the time, if we deal with a lesion on the acetabular side which, as we discussed earlier, it's more frequently, if I have carpet delamination versus a wave sign or a subchondral delam without a flap, I will advance the labrum, do my trim, advance the labrum. But then if we're left with a residual grade four, my go-to procedure still is the microfracture, and this is work in progress. Now our patient, in addition to having the microfracture protocol, we start to use losartan and we're doing a clinical trial with that medication right now, which blocks TGF-beta 1.

                                                You might know we did an animal study comparing a microfracture versus microfracture plus losartan. We found in the microfracture plus losartan group a 92% higher in collagen versus 40% of the microfracture group. We published that study and based on that now we're going to humans clinical trials. We feel that microfracture with the appropriate rehab protocol on the acetabular side as giving us very good outcome for chondral lesion.

                                                We also publish in Arthroscopy return to sport in the professional athlete for patients with FAI surgery, with and without microfracture and return to sport was the same. But also we look at their statistics and they were the same in the microfracture group and the non-microfracture group for FAI treatment, so we feel that on the acetabular side, it's a very good procedure. On the femoral head side, if we have good shoulders to contain the clot, we also perform microfracture.

                                                Now you're going to ask me probably about the size of the lesion. If the size is too large on the femoral head size side, I've looked and I have performed osteochondral plugs successfully. But most of the time I have to say that what we see in our practice is often traumatic injury of the femoral head. As long as the subchondral defect is not too deep, microfracture also works really well in the femoral head site. But I have also used collagen membrane, have used various other technique as well in certain situation. But I still feel the most predictable result in my hands are with the microfracture.

Dr. Justin Arner:               I think the technique really is important, like you mentioned, with the good shoulders and making sure you perform a microfracture appropriately and the adjuncts, I think, that you and your team perform with circumduction and the losartan, I think really make a big difference. So I think it certainly is dependent on how you do all those techniques.

                                                Thank you, Dr. Philippon, for sharing your thoughts with us today. I'd really like to thank you on behalf of all the listeners for being such a giant and pioneer in our field. You've taught us so much about the hip and continue to with your numerous innovations and really high-quality research. So thank you for all of that and thank you for your time today, Dr. Philippon.

Dr. Marc Philippon:         Thank you, Justin. Again, congratulations for your work and creating this podcast.

Dr. Justin Arner:               Thank you. Dr. Phillipon's article entitled, “Predicting Severe Cartilage Damage In The Hip: Model Using Patient-Specific Data From 2,396 Hip Arthroscopies,” which is published in the July, 2019 issue of the Arthroscopy Journal and is available online at www.arthroscopyjournal.org. Thank you for joining us.