Name: Diagnosis and Treatment of Atypical Impingement
Uploaded: 2016-07-19T00:00:00Z
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VPT1-00673-EN | A | Diagnosis and Treatment of Atypical Impingement

Asheesh Bedi

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Diagnosis and Treatment of Atypical Impingement

We fortunately talked a little bit about this already, but it's sort of talking about where we're extending now beyond just the intra-articular cam and so-called pincer and other things that can then create can create a conflict. So, you know, we've had great talks on this this morning, Tom and others on cam impingement. You know, this out of round asphericity that leads to this delamination and primary injury to the contralateral junction. And that's a little bit easy for us at least to mechanically understand. And then the the counter side of that, which is the rim impingement, where there's an area of focal acetabular retroversion and rather than delamination of the contralateral junction, this leads to impaction of the labrum induration and edema and sometimes ossification as a distinct mechanism of injury to the joint. But it's not always cam and pincer impingement all all of the time. And sometimes, for all of us who are caring for these, it's it's humbling to see you can flex a hip up to 90 or 100 degrees in what otherwise looks like a hip without cam or pincer impingement, and have and have a mechanical block to motion, and that can sometimes be extra articular impingement, which can either reflect deformity of the pelvis or proximal femur, or a combination of both. So while this becomes a little bit on the fringe of topics, it's at least important for us to identify not because you'll be treating these every day, but. But sometimes the more you see these patients, the more you want to identify them, because you may perform a cam and pincer resection and be disappointed that you didn't get an improvement in range of motion and symptoms. So the three major groups and Brian touched on this yesterday are our sub spine impingement, which is a really a pincer variant of extra articular impingement. Trochanteric pelvic impingement where the trochanter hits against the pelvis. This x ray is an extreme case of that of a Perthes hip that leads to coxa vara, coxa brava, or a short neck, and then, correspondingly, an increased risk for the trochanter to contact the pelvis. And then these cases that we're recognizing some of now femoral impingement, in this case from an old proximal hamstring avulsion that decreases the space between the lesser and the pelvis. So let's start with the first one of these that largely has been popularized by Chris Larson and Brian Kelly and others, which is sub spine impingement. And the concept here is that there's direct impingement from the anterior inferior iliac spine with actually the distal femoral neck, primarily with direct hip flexion. This isn't there all of the time, but it is there in certain cases. And this is one of those extreme type of cases. You can see here in eyes that you would pick up on the false profile image or virtual false profile on the right here you can see on the CT scan. This likely represents an old apophyseal avulsion of the rectus that has healed in an elongated position. But the net result is is that the eyes is actually caudal to the acetabular rim. As you flex this hip up dynamically. This is that type of simulation software. You can appreciate that the first thing that contacts is not this patient's Cam lesion or rim lesion, but in fact it's the sub spine. And it restricts flexion at 100 degrees of flexion. As you go back and flex that you'll appreciate that where it makes contact is actually very distal on the femoral neck. And that's sometimes when you see that see that sclerosis or Cam lesion that's more symptomatic distally, perhaps that reflects this mechanism of impingement, which you wouldn't be thorough about treating if you just did a small proximal resection here. When you eliminate that and convert that to more of a normal morphology. The hip can flex up another 20 degrees. So again, just pointing out that sometimes if you see or feel a mechanical block to motion, that doesn't make sense with your conventional cam or pincer mechanism, be aware that sometimes these extra articular variants are there. This is an example of that with such a deformity. Again, where do you see it? Three dimensional imaging I think helps. Here. You can see when you rotate the pelvis where you get this four rotation view the right view called the ischium view. It's sort of a false profile which gives you a sense of what the relationship of the eyes is to the acetabular rim. If you're not into three dimensional imaging, you can still pick it up on your false profile view. That's your best view to look at it both to assess the joint space, but also to assess that relationship. As I mentioned, this was largely popularized first by Chris and Brian. This was a case series that they published. Again, these are kind of those extreme cases that highlight it. You can see something is off here with the left hip. That extension of bone is not the acetabular source seal. When you get the CT scan you appreciate it has this kind of an extent to it. And it's important to recognize this because a lot of us have relied on this so-called crossover sign to determine a pincer impingement. But what we did, this is a series I did with Brian and IRA, where we looked at patients that had a crossover sign on their x ray. And sure enough, what you realize is about half the time that crossover sign isn't from the acetabular rim at all. It's from this area of the eyes that extends down to create a false profile view of, of a of a crossover. That's, of course a danger, because if you go in those hips and perform a pincer resection, probably the only thing you've done is create some dysplasia for them, but you haven't treated their mechanical block or deformity. So these are those kind of cases. This is one example from Chris actually. Again you can see an extreme or so-called type three sub spine where it extends down below the acetabular rim. On the false profile here you can see on the CT that's going to be your clear block deflection. And again in these cases you want to treat this. And this is just a video that will hopefully play in and show that the important reason to to to be aware of this on your pre-operative imaging. This will not see you unless you go looking for it. So if you just do your routine exposure of the extra capsule or tissue, you won't see it. You have to make a small window here, either through a little slip in the rectus, and really extend your resection far proximal to the to the acetabular margin. You can see that there's a broad footprint of where the rectus attaches to the eyes. It's actually a study done by by Chris and and owner Hoppa that shows it's about a two by two centimeter broad insertion. So you can really carry this resection quite proximally in the bare area of the eyes and not disrupt the rectus attachment. But again, there would be no reason for you to continue that resection or elevate the capsule that proximally, unless you were looking for and aware of it on your pre-operative imaging. So again, just something important to note because it likely sees us more than we see it if we don't go don't go looking. And this is how that X-ray should change. This is one from Chris that shows that preoperative image on the top left and bottom left. And then what it looks like on your false profile on the right, and the associated studies with that. Well, what about some other zebras that are out there? We talked about the acetabular side with some spine impingement. It can happen a little bit on the femur as well. And again, this is why the more of this I've done, the more I've felt the importance of getting some form of three dimensional imaging. Because remember femoral version plays into range of motion and it can be torsion or version at any point along the femur. Remember we're used to thinking about version from our total joint colleagues where we measure the posterior condylar axis and we look at the angle of the femoral neck. But a femur can be paused at the intertrochanteric level at the sub trochanteric level, at the shaft level. And it doesn't much matter except for that. It of course affects our hip range of motion. It does matter, though, when we think in terms of range of motion and impingement. And this is a good example of that. These are for example, if you were to get an MRI of a hip or a CT of a hip without getting cuts at the knee, these would these would be two different patients, both of whom could come back to you with a radiographic report of impingement and an alpha angle of 57 degrees. But I think you'll appreciate that the top patient has absolute Retroversion of six degrees, so their ability to engage their cam lesion is pretty significant. Just a small amount of internal rotation will engage the cam. And they're going to be very restricted with the same Cam lesion. Take patient number two who has a similar alpha angle but has 21 degrees of anteversion bordering on bordering on excessive anteversion. They now have a reserve of about 20 degrees before the cam engages. So the same lesion can be very differently symptomatic. And it would be important for you to know that in terms of treating that patient. So this is kind of that concept here. So if you have these unique cases here you can see one of coxa vara looking like a Perthes hip on the left. You might sort of get focused on the joint and treat what might be quote unquote cam type impingement. But I think you appreciate here that the issue might be the trochanteric pelvic impingement and a case where you might want to do a relative neck lengthening to alleviate that as the mechanical cause. Well, why do we need to to have this surgical dislocation in our armamentarium? It doesn't mean that you have to do it. I certainly don't do a good one, but I'm always prepared to have a Jocelyn LaRue or an eye results around to, to treat that. And the reason for that is it's still a powerful tool for these extra articular cases where the impingement is from the greater trochanter. And this is that concept here where you may not be able to reverse the Perthes remodeling, but you can at least alleviate the source of mechanical deformity by cutting the trochanter, destabilizing it, and relatively lengthening the neck. Again, most of us aren't seeing all of these patients, but as you see more and more of these hip patients in the clinic, you will see these pediatric patients eventually become adults and show up in your clinic. And remember, these are cases that are unlikely to be addressed well with any arthroscope. As you can see with a skiffy, there's not just a Cam type deformity, but there's a translation of the epiphysis. There's a relative negative offset of the head and neck junction. None of those are going to be effectively treated without an intertrochanteric or cuneiform type of osteotomy to restore that normal sphericity offset, but also length to the neck and similar issues with a Perthes deformity. There's sort of some of these subtle cases. These are a bit more subtle. This is a case actually, of Ernie Sink and Brian's, where you can see this excessive anteversion that leads to a decreased space between the trochanter and the ilium. So maybe in these cases, even though the hip isn't unstable, if they're feeling impingement from the trochanter, and again, not something that we do very often, but it might be a case where you actually shift the position of the trochanter to alleviate that source of mechanical impingement. Ira, on some of the open surgeons, have done good work under ultrasound to show that you can look at that. You can look at the contact between the trochanter and the ilium in provocative positions of extension and external rotation, and get a gauge of that correspondingly similar with with a retroverted hip. Can you do this through the scope? You can sometimes in these extreme cases here you can see this example where the trochanter is relatively proximal. And that may be the source of impingement. But I think this speaks to what Tom just talked about, the importance of being thorough with your cam resection, not just stopping proximally, but carrying that camera section all the way distal to the to the intertrochanteric line. And in my hands, that requires a t capsulotomy in most of those cases. Remember there's these unique cases of focal residual disease. This actually happens to be a Perthes hip that I cared for. You can see he's got lateral column disease. That's residual deformity with a cyst at the head neck junction there. This is maybe one that you can treat with an arthroscopic approach. But remember these are the exceptions rather than the rule. Finally, this may be the last form of atypical impingement to discuss as ischiofemoral impingement. You will see this the more you see these patients who had had a previous proximal hamstring rupture and had this significant Arrow related to it. His complaints were sciatic nerve symptoms every time he sat, and an inability to extend and externally rotate his hip. And so, as you can imagine, in these cases you can get focused on the joint. But clearly the rate limiter is the contact between the lesser and this bone fragment. This is obviously an open surgical solution that would require excision of the repair of the proximal hamstrings and potentially a sciatic neurolysis. You can diagnose these by looking on the MRI for it. Here you see edema in the quadratus femoris and in your short external rotators, you need to see this. You need to measure the space between the the Ischiofemoral region and identify this on your exam with pain with particularly extension and external rotation. It's a case of Chris Larsen's that shows the same here. This edema and this decreased space in that location. Again this happened to be that case where we had to excise that area of H0 re advance and repair the proximal hamstring, decompress, in this case actually resecting the lesser trochanter. It's a case of Brian's where they've done the same again repairing the proximal hamstrings to the footprint. And here you can see on the post-operative image even resecting the lesser trochanter. So in summary, I think arthroscopy has a good and evolving role for these atypical impingement cases, certainly for spine impingement in some cases of trochanteric pelvic impingement, but don't necessarily choose the approach. Let the pathology choose the approach. And so be prepared for a potential open surgical repair if you need to to address these cases.

Diagnosis and Treatment of Atypical Impingement

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