Hospital for Special Surgery Perspectives

A Closer Look at Hip Impingement and Return to Play

Anya Romanowski, MS, RD

July 05, 2017

Editorial Collaboration

Medscape &

Femoroacetabular impingement is a condition of the hip joint in which bone overgrowth causes an abnormal shape and friction in the ball-and-socket joint. This leads to joint damage, pain, and limited mobility.

Bryan T. Kelly, MD

Medscape recently spoke with Bryan T. Kelly, MD, who specializes in sports medicine injuries and arthroscopic and open surgical management of nonarthritic disorders of the hip, to find out more about treating femoroacetabular impingement and expectations regarding hip preservation surgery. He is chief of the sports medicine service at the Hospital for Special Surgery and a professor of orthopedic surgery at New York Presbyterian's Weill Cornell Medical College in New York.

Current Thoughts on Hip Impingement in Athletes

Medscape: Can you describe your primary area of interest in orthopedics and your current research on treating hip impingement in athletes?

Dr Kelly: The question is whether treatment of impingement changes the natural history of chondral degeneration of the hip joint. We are looking at quantitative MRI images at 5 years postsurgery and comparing these with images from age-matched controls with similar mechanics who haven't had surgery, to see whether there's any difference in the chondral protective effects of the surgery.

My primary area of interest is femoroacetabular impingement, which is considered a prearthritic condition in the hip joint. In terms of research, the areas of interest are the impact of treatment on alleviation of early symptoms, and the ability of athletes who have been sidelined by this type of injury (to the cartilage inside the joint, particularly the labrum) to return to play.

We are also looking at the long-term benefits of treatment. Is there a hip preservation component to it? Does it provide a kind of protective benefit to the joint long-term?

Medscape: Are there particular sports that have more of an impact to a player's hip in terms of injuries, and which athletes have better outcomes from this procedure?

Dr Kelly: We spend a lot of time looking at sports-specific differences. If we look at the epidemiology of the athletes whom we treat, the most common sport is ice hockey. The other sports that are high on the list are lacrosse and soccer, which are land-based cutting sports. Other sports (such as football, baseball, and basketball) are affected by it, but it doesn't seem to be quite as prevalent.

The thought as to why that may be is that many of the morphologic variations we see in association with an impingement on the hip are related to the mechanical forces that the hip joint is subjected to in the development phase, before the growth plate is closed. If the immature growth plate is subjected to a lot of torsional forces before the femoral head is completely fused, alteration of the femoral head anatomy occurs, resulting in these bumps of bone that can lead to overload to the cartilage and labrum at the front of the hip joint.

That's probably why the joint is subjected to a lot of rotational torque in those cutting sports, such as ice hockey. Early research has been done looking at the actual mechanical loads that the physis may be subjected to in such sports as ice hockey, and there do seem to be increases in the physial loads. Once you have developed this nonspherical variation of the head and you're continuing to participate in sports where there's high flexion and rotation, that leads to these high-load contact points. So that's why we see it in those sports.

Return to Play Rates After Arthroscopy

Medscape: What influences an athlete's ability to return to play?

Dr Kelly: The ability to return an athlete to play is very high. We and other researchers have shown return-to-play rates at or above the level they were before their injuries (anywhere from 80% to 95%), depending on the level of the athlete in the studies. Arthroscopy is a good procedure to eliminate symptoms and get people back to play.

Probably the biggest thing that affects the ability to return to play is the severity of the cartilage wear. If there is progressive cartilage wear inside the joint at the time of the indexed procedure, then the prognosis is not as good. You want to intervene before this permanent cartilage wear occurs.

Different, more complex mechanical anatomy can coexist in the setting of impingement (mild forms of hip instability, excessive rotational deformity on the proximal femur, and socket deficiency). Instability and dysplasia are not well treated arthroscopically in the setting of impingement.

Medscape: Are there any differences in how the procedure is performed that have an impact on outcomes?

Dr Kelly: The first challenge is an appropriate indication. The diagnosis of symptomatic labral pathology in association with pathologic hip impingement (which is what we're treating) requires more investigative work when you're making the clinical diagnosis than whether or not you dislocated your shoulder or ruptured your anterior cruciate ligament. It's usually not an acute event; it's a chronic injury based on mechanical overload.

Understanding the specifics of the mechanical overload is important, because some types of problems are treated more or less easily with different types of surgical procedures. We have recognized that there are certain forms of occult or mild hip dysplasia (which is where the socket is shallow relative to the femoral head) that can be present in the setting of hip impingement. It is important to figure out what the dominant mechanical overload problem is, because dysplasia isn't treated well with arthroscopic surgery. The surgeries can be technically challenging to do well in making sure you have an adequate correction of the anatomy.

Postoperative rehab and having a good physical therapy program that can get the muscles to start firing properly, and build up their strength, endurance, proprioception, and sequencing (which are the phases of therapy), are really important. There are 27 muscles that surround the hip joint, and three to four layers of muscle. It's a much deeper joint than the shoulder or the knee, and the effect of the surgery in terms of the associated dysfunction and the musculature around it can make recovery a little bit more challenging.

And then the fourth phase is return to play. Return to play can be very challenging with any joint, and probably the one phase that is least supervised in our culture here, where athletes get discharged from therapy and cleared to return to play by their coaches.

To me, these are the four most important things: appropriate diagnosis, good technical surgery, good physical therapy, and good return to play.

Medscape: Is there a certain age group that has more favorable outcomes with this procedure?

Dr Kelly: Younger is better, only in the respect that there's typically less cartilage wear in the younger patient because there's been less time to create permanent cartilage wear. There is some question about the open growth plate, and whether or not it is advisable to operate and change the shape of a hip that hasn't fully fused yet. There's some concern that some regrowth of bony deformity may occur if these surgeries are performed in patients with an open growth plate. To date, there's been little research to prove that it's a clinically significant problem. However, we do have anecdotal and occasional evidence that open growth plate surgery may lead to recurrence of the impingement.

In general, I feel that these procedures are perfect for patients between the ages of 16 and 40 years. Occasionally, you'll see patients younger than 16 years who develop symptoms. If you have a 13-year-old who already has early impingement, you have to decide whether you want to wait for the growth plate to close, or whether you want to be more proactive about it. These are unusual occasions, and we don't have a consensus on what's the best way to treat these patients.

On the other hand, there are people over 40 who have healthy cartilage. But if you're over 40, the likelihood of having more permanent cartilage wear and tear, areas of full thickness, condylosis, and thinning are all potential things that compromise the ability to have a successful outcome.

Acetabular Rim Considerations

Medscape: In one of your research posters, you focused on the "danger zone" of hip arthroscopy and compared two techniques used to insert suture anchors during labral refixation. Can you talk about your findings?

Dr Kelly: This poster examined the technical aspects of the surgery. Access to the acetabular rim in the hip can be a little bit more challenging than access to the glenoid in the shoulder. Some people liken the hip to the shoulder because of the ball-and-socket joint. In terms of access, there are some angular problems that you need to be cautious about.

If you think of the acetabular rim as a clock face, most tears exist between 12:00 and 3:00 in the anterior-superior region. As you get more toward the 3:00 position, you have to be cautious about penetration outside of the acetabulum. There are two locations you can penetrate: The anchor can go into the hip joint, or it can penetrate the base of the anterior-inferior iliac spine, where the iliopsoas crosses the iliopectineal eminence on the acetabulum. That can lead to irritation in the psoas and some postoperative complications.

This poster was suggesting that as you get more anterior, you should change your portal access to make sure that you reduce the risk of having these perforations into areas that you don't want to be into.

Expectations of Hip Preservation Surgery

Medscape: Another paper described a new approach of using outcome score thresholds to compare what a patient perceives as considerable improvement after a hip procedure. What inspired you to take on this research in looking at these scores?

Dr Kelly: The biggest questions that we have in any of the surgeries, particularly new techniques, are: Are we satisfying patients' goals? Are we meeting their expectations? Are we making them better?

Traditionally, people have looked for statistical significance and outcome scores. You take a modified Harris Hip Score, where a perfect score is 100, "unable to ambulate" is 0, and everything in between gets a digit. You say, "Well, the patient came in, and their Harris Hip Score was 78 points. After the surgery, it was 86 points." And we do some stats on it. We say, "Well, that's a statistically significant difference. Therefore, that was a good outcome." We have randomly assigned values (< 70 is a poor outcome, 70-80 is fair, 80-90 is good, and > 90 is excellent). But these are kind of random.

You can have a high-level athlete who comes in, and they score a 96 preoperatively on their modified Harris Hip Score. After surgery, they can participate in their sport, and they end up with a 97. That's not a statistically significant difference, but it was a meaningful difference because the patient was able to return to play.

I think both the minimal clinically significant difference and the substantial clinically significant difference are trying to avoid ceiling effects and really look for what ultimately we hope to demonstrate to be more clinically relevant ways to interpret how people feel about their surgery in terms of whether they get better or not. These different statistical techniques are used to try to examine that question and seem to have more scientific merit to them.

A very interesting expectation study by Carol Mancuso and colleagues[1] was recently published in Arthroscopy.[1] Expectations of what the patient wants from surgery oftentimes affect their satisfaction with the surgery. If they say, "My hip hurts, and I can't sit. I can't sleep at night. I expect that after the surgery, I'm going to run ultramarathons," we might reply, "Well, that's not a reasonable expectation. But would you be happy if you could sleep at night, and you weren't requiring pain medication throughout the day?" And they say, "Well, maybe if you put it that way, I would be." You've reset their expectations.

One of the things we've found in this particular field is that the symptoms people have associated with this type of problem (symptomatic labral pathology with pathologic impingement) can be quite debilitating. They are highly active individuals, and their expectations are very high. Trying to match what their expectations are with the likelihood of their outcome is important. I think the minimally clinical and substantially clinical differences that Ben Nwachukwu and colleagues have worked a lot on help us understand the impact of expectations on outcome.

Computer Navigation Techniques to Assist in Surgery

Medscape: Have there been any recent technical advances as far as using robotic arms or other computer devices to assist during surgery?

Dr Kelly: Yes; we've actually worked on computer navigation techniques to assist in the surgery, and computer-simulated collision models. The surgery is classic surgery for the hip, and we're trying to make the mechanics better. If you're starting off with a square peg in a round hole and you want to make it a round ball in a round hole, you need to know where you're starting from and where you need to sculpt the bone properly.

Up until now, we've utilized two-dimensional imaging with plain radiographs and MRI to look for soft-tissue injury patterns, and then eyeballed it at the time of surgery—which can be challenging, because you're trying to recreate a concavity around a sphere, looking through a 70° scope that only looks at 10% of the whole field at one time. So you have to recreate the three dimensions in your mind. Three-dimensional CT before surgery is being utilized more and more. It allows us to develop a model of the hip to see exactly what the shape looks like, so we know what we're starting with, and remove it.

With collision models, where we actually move the hip on a computer and see where the contact points occur, we have the ability to perform a simulation of the surgery on the computer. We say, "If we take bone here and here, and then do the same thing, will it fit better?" And then bringing that into the operating room, we have a preoperative image that's in three dimensions. We have a collision model, which shows us where the mechanical contacts are occurring. We did a simulated surgery on the computer. Now it's more than just eyeballing it. We have a real template that we can bring in the operating room.

The final step would be to have a robot do it for us, but we haven't gotten to that point yet.

Medscape: When I spoke to Dr Alberts, he said that for the surgeon who has performed a procedure a zillion times, robotic surgery it isn't going to have as much of an impact. But for a younger, less experienced surgeon, it would be more appropriate to use the robotic arm.

Dr Kelly: That's very true, but if we look at revision hip surgery and the risk for failure, the number one reason for it is that there was inadequate or inappropriate resection of bone. You didn't do a good job, and the computer could at least help you avoid not doing a good job. There's technical things you have to do, and at the end, you have a pretty good critique of whether or not you did what you were supposed to do by the end of the surgery. Moreover, it could incentivize people to keep at it until they're done, rather than just sort of throwing in the towel too early.

Medscape: Are there any final comments that you have on any other advances that you'd like to share with other orthopedists?

Dr Kelly: I think this is still an emerging field, and our level of understanding of hip impingement and how it affects quality of life as well as the wear of the hip joint is exciting. We've made a lot of advances in it. The pathology is amazing to me, in terms of how much damage it causes. Our ability to reduce the rate at which things wear down is an exciting field to be in. The way you can positively affect people's lives by giving them their life back and function back is very encouraging.

There's still a lot that we need to know in terms of appropriate patient indications, and there's certainly a very good group of patients who are perfect for the surgery. However, there's a much larger group of patients who are kind of on the fringe, and I think we need to continue to learn more about the different indications, and what things make it more difficult to have a successful outcome. I want to focus on the patients whom we can really help, but continue to try to learn about the ones we haven't quite figured out yet. And I think we've made a lot of progress over the past 10 or 15 years, but there's still a lot that needs to occur.

Bryan T. Kelly, MD, has disclosed the following relevant financial relationships:
Serve(d) as a director, officer, partner, employee, advisor, consultant, or trustee for: Arthrex

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