2025 Great Debates: The Hip-Spine relationship does not matter for Anterior Approach

Great Debate: Does the Hip-Spine Relationship Matter for Anterior Approach?

🎙️ Join Joe Schwab in this intriguing episode of the AHF Podcast, where Dr. Nathaniel Nelms and Dr. Edwin Su debate a hot topic in orthopedics: 'Does the hip-spine relationship really matter for the anterior approach?' With thoughtful arguments from both sides, this episode delves into the importance of biomechanics and surgical techniques to achieve stable, durable, and predictable hip replacements. Whether you're a surgeon or simply interested in the nuances of anterior hip surgery, this discussion will sharpen your thinking! 💬 📌 Tags: #AHFPodcast #GreatDebates #AnteriorHipFoundation

Transcript

Joseph M. Schwab: 0:00

Hi, this is Joe Schwab and if you recognize my voice, it's probably because you've heard another episode of the AHF podcast, which means you're listening again, and I can't tell you how much I appreciate that. And because you're listening, again, I want to ask you a favor, if you could share this podcast with a colleague or a friend or somebody you think might be interested in this type of content. Or better yet, leave us a review on your podcast platform or give us five stars, or you could do all of those things. We really appreciate it and it helps us grow. Anyway, thank you so much for being a listener and a subscriber to the AHF podcast. Now let's get on with the show. Welcome to the AHF podcast. I'm your host, Joe Schwab. One of the reasons we host these great debates is pretty simple. Orthopedics moves forward when thoughtful surgeons disagree respectfully. So much of what we do in the operating room comes down to judgment, often more judgment than maybe we'd like to admit, and when the evidence isn't definitive. When two smart people can look at the same set of data and reach different conclusions, that's exactly the moment when debate becomes valuable. Today's topic is one that every anterior hip surgeon has wrestled with in one way or another. Does the hip spine relationship really matter for the anterior approach? Taking the pro position, we have Dr. Nathaniel Nelms taking the con position. Dr. Edwin Su. What you're about to hear isn't just a clash of viewpoints. It's a glimpse into how experienced surgeons think, how they weigh risk, and how they decide what matters in the pursuit of safer, more reliable outcomes. Let's get into it. The next debate topic is:"The hip spine relationship does not matter for anterior approach". Taking the pro position, Dr. Nathaniel Nelms, taking the con position, Dr. Edwin Su. Four minutes to you. Dr. Nelms.

Nathaniel Nelms: 2:33

Thank you very much. I posit to you that this is the most important debate that you guys are going to face. In your practice at all? I think that in everything we hear, we need to do more, more, more. You need technology, you need the robot, but have you guys all been made to feel guilty if you're not getting five extra hip and then spine x-rays and then all this extra technology? But I ask, where is the evidence? There is not one study that's published when it comes to anterior total hip that demonstrates any advantage to using the hip spine relationship period. End of debate right there. So you do not need to have functional spine x-rays, a full body EOS CT, save that for the posterior robotic total hip patients. First, let's come back to what's the problem. All that the hip spine relationship was ever designed to deal with was dislocation. And the problem came because surgeons that were doing their patients in a lateral position. And, um, we're having dislocations despite using navigation in robotics. Why was that? It was because they were putting the cup in a position relative to the pelvis, but not thinking about the functional position, which we can get just by laying the patient's supine and doing an anterior hip. The pelvic tilt is already accounted for when you use fluoroscopy and put the cup in an appropriate position. You're already taking into account those differences in pelvic position. So when it comes to evidence, is there, uh, any evidence? The hip spine relationship is important. Absolutely it works in the posterior approach. For the anterior hip, there is zero. Vigdorchik one of the founders of this principle. He applied this to a large group of patients. He found he was able to bring his dislocation rate down to 0.8%. That's still higher than most series with the anterior approach. And to do that, he had to use eight dual mobility. In 8% of his cases. Do we use dual mobility? 8% of our cases. We don't need to. It's an unneeded expense. There was a study in JOA in 2024, looked at 180 anterior versus 180 posterior approaches all two Bs. The worst hip spine classification, there was 0.6% dislocation in the anter approach. That's about the same as in the studies that aren't using it, and 2.7% in the posterior approach still not as good. So why does approach matter? It's because we're able to lay the patient's supine, but also we're able to disrupt the tissues less. You can keep your obturator externus intact. You can keep your posterior capsule intact, maybe repair your anterior capsule. Your stated goal could be wrong in making these corrections. You could actually make the problem worse. You could, IM measurement errors. It doesn't always take into account hip flexion contracture. Think about that. And femoral anteversion is often not even considered in the whole thing of, am I gonna adjust my composition? When you look at what's recommended in hip spine classification, if you put your cups at 40 degrees and 25 degrees of anteversion, you're gonna hit all of them, your one a's your two as. Two, two B's. Two, two a's all of those are included. So the difference you're gonna make is maybe five degrees in composition is always changing. Just the anteversion, you're really not making any difference at all. So what does matter? Do an anterior approach. Minimize soft tissue releases, recreate your leg length and offset. Stop worrying about this little tiny change of cup position that you can't actually make. Even with the robot, you might be hitting the wrong target. I yield my time.

Edwin Su: 5:37

Nathan, Nathan. Nathan. Uh, boy. Am I gonna school you? Uh, this is my first, uh, invitation here and, uh, I feel like I just got invited to a special club. So thank you to the organizers. Uh, so I, I, I, um, I'm gonna start this debate with a survey. So, how many of you are using fluoroscopy for your DA total hip replacements? Show of hands, please. 93 people. Okay. How many of you are positioning your cup based on the standing pelvic position? Show of hands. Okay. Not as many as I thought actually. Uh, so, um, well, I would argue that if you are trying to position your cup at the time of surgery to the standing pelvic position, then you are already taking into account the hip and spine position. And the mechanics and how it affects your, uh, cup stability, your hip stability. So you said that there were no holds barred for this debate. I tried to look up all dirt on Nathan. Uh, he runs a pretty clean ship. I didn't see any, uh, evidence on social media, so fortunately didn't have anything. Uh, but that may be because he's been living under a rock and he hasn't seen in the last five years about a hundred pa papers written about the hip and spine relationship. I wish I could believe your magical thinking, that DA approach could make our dislocations disappear. But we can't overcome the laws of physics. We are making an incision. We are gonna disrupt the soft tissues more in the anterior than the posterior granted. And I think you'll all do a beautiful job, and that's why we're here talking about the DA approach. But our dislocation rate will not be zero. The the ball that we insert is smaller. We have the soft tissue compromise and the hip spine mechanics will influence where the pelvis is in space. And we have to take that into account when we position our cup. The two situations where that's important are in the stiff spine and in pelvic tilting this will occur because the pelvis is a bridge between the hip joint and the spine. So Nathan, the hip bone is connected to the pelvis bone, which is connected to the spine bone, and that is why we need to take this into account. Okay? He's given some eloquent, uh, arguments that you don't need to take that to into account because our soft tissue envelope is good. Um, but I would submit to you even in those papers that show there, there is a reduced risk of dislocation with the DA approach. It is not zero. And you all are surgeons here who are interested in education, learning from others, and doing the best for our patients except for Ben Domb, who just came here for the social events. But, uh, I would submit to you if you are interested in that. Then you must take into account the hip and spine relationship. So from a practical standpoint, you don't need to get 14 studies, you just need to realize that the spine does influence the pelvis. And basically the two situations that I'm concerned about that keep me up at night are the stuck standing position where the pelvis does not roll back in the sitting position and then you're at risk for posterior dislocation. And I will give you that. The DA approach, I think mitigates. That to a large degree. So most of the time you don't really have to worry about that stuck standing position. It's the stuck sitting position that you really have to worry about when you look at that standing pelvis, and it looks like an ob, an outlet view, they are basically posteriorly tilted and they're gonna be at risk for anterior instability, and those are the ones that you have to be careful about. Minimize your cup position and even minimize your anteversion on the cup and consider dual mobility. So, um, in conclusion, Nathan, I think if you wanna do the best for your patient, you need to realize that the hip spine mechanics are a risk factor for dislocation. You recognize risk factors for other conditions and you don't ignore them. Why ignore the hip and spine relationship?

Joseph M. Schwab: 9:29

One minute rebuttal.

Nathaniel Nelms: 9:31

Wow. Um, I don't believe any of that. Let's start with that. Um, I think maybe what we should all do is do hip resurfacings. Like you, I'm sure you use all the hip spine classification for every one of your hip resurfacing patients you take care of. I just question, you know, I just go back to my points of, um. You know, can we keep it simple? Your goal is maybe to get it to 0% dislocation. Is that reasonable? Is that possible? There are some patients who have soft tissue abnormalities, they're hyper lax. Some of the recommendations from the, uh, hip spine classification are go dual mobility. Well, if, if you have to go dual mobility, can you really get an optimal composition that's gonna get you to 0% dislocation? So maybe we could get closer to 0% if we just put, dual mobility in all of our patients. But we're not gonna get there. Even doing that. There are weird things that happen. We all absolutely want to do our best, right? Do it. But this isn't gonna get us there.

Edwin Su: 10:26

I think it'll, I think it'll get us closer, Nathan. So if we recognize that in that, in that, uh, situation where the spine effects the pelvis, we can modify certain things, just little tweaks and try to get it as close to zero as possible. I think we're on the same page, but I think you should take into account the hip spine mechanics.

Joseph M. Schwab: 10:44

All right. Thank you. Thank you, debaters. Please go to your app. Vote for who won. At the end of the day, whether you lean towards Nathan's call for simplicity or Edwin's emphasis on biomechanics, there's one point they both agree on. Our goal is the same. We're all trying to give patients the most stable, durable, and predictable hip replacement possible. Some of us approach that by reducing variables. Others approach it by trying to measure and account for them. And the truth is both philosophies have merit depending on the patient in front of you. Hip spine mechanics won't matter for everyone and they won't matter in every case, but they do matter when they matter. And part of being a thoughtful surgeon might be knowing when that moment is. If today's debate helped you sharpen your thinking or reconsider your assumptions. Then it accomplished exactly what these conversations are meant to do. Thank you for joining me for this episode of the AHF Podcast. As always, please take a moment to like and subscribe so we can keep the lights on and keep sharing great content just like this. Please also drop any topic ideas or feedback in the comments below. You can find the AHF podcast on Apple Podcasts, Spotify, or in any of your favorite podcast apps. As well as in video form on YouTube slash at Anterior Hip Foundation, all one word. Episodes of the AHF Podcast come out on Fridays. I'm your host, Joe Schwab, asking you to keep those hips and spines happy and healthy.