Name: The Dog Bone Technique for AC Joint Reconstruction
Uploaded: 2016-10-13T00:00:00Z
Channel: Arthrex

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VPT1-00698-EN | A | The Dog Bone Technique for AC Joint Reconstruction

Paul C. Brady

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The Dog Bone Technique for AC Joint Reconstruction

The anatomy of the AC joint consists of the conoid, the trapezoid and the AC joint capsule, the conoid. If you look at the conoid, it goes from the medial base of the coracoid and to the medial side of the clavicle. The trapezoid goes from essentially just the top of the clavicle to more anterior on the clavicle. Here's the undersurface attachments on the clavicle. The conoid medially inserts about 46mm from the AC joint. The trapezoid is about 25, so I typically shoot when I'm doing a osseous technique. I typically shoot for the middle of those two, which is right about 30. Okay, so three centimeters from the AC joint. The conoid is a little more posterior, the trapezoid more anterior. So if I go right for the middle of the clavicle, I think that's a pretty good space right between those two. So what's the mechanism of injury? Typically it's a direct blow, but sometimes people become quite creative with their mechanisms and I've seen pretty much everything. So the normal AC joint motion, it has a little bit of motion with abduction, adduction and flexion. And there is normally a small amount of anterior posterior translation of about a one and a half to two millimeters. Here's a good. This is an article which had a good reproduction of that with with shoulder abduction as well as flexion. You can see not only does that distal clavicle rotate, but it translates a little bit posterior a little bit of anterior. And if you look at it from a different perspective and and the clavicle is stationary and the scapula is moving around it, you can see that it does it does translate just a little bit both rotationally as well as anterior posterior. So the classification, the Rockwood classification, the problem with the Rockwood classification, it's what we all use. It's probably what we'll always use. But one of the problems is that it really doesn't incorporate anterior, posterior or rotational stability. And I think that's a subject that's becoming much more pertinent in our treatment of AC joint injuries. Associated pathology is something important to remember. You do have a fairly high incidence of associated lesions when you have a patient with a grade three AC joint dislocation. We looked up the group in our brass group of 98 patients. We found about 43% had an associated lesion. About 30% of those required an additional surgical procedure at the time of their AC joint reconstruction. And if you're over 45, you had about a three time incidence of associated pathology. Now, again, the study didn't look at causation but this is association. What about the examination and assessment of the AC joint. So it's important to recognize is it reducible. Is it reducible when the patient shrugs their shoulders. Or is it reducible to palpation. How much anterior posterior instability is there when and when you reduce it, does that AP stability improve. And then is the deformity worse with external rotation? Or as I'll show you sometimes with forward flexion and then a cuff exam. And so so let's look at the one little pearl I have here as far as the diagnosis. And so this is a patient who doesn't look too bad until he leans forward. And then you can really see that thing pop out. And he puts his elbows on his knees. Now if he tries to put pressure on his elbows on his knees, you can see that there's significant anterior posterior translation of that distal clavicle. And this patient remained quite symptomatic. Imaging. Gus Mazeika showed me a few views that he always gets. One is is called the shrug test. He has the same view with the patient shrugging. And if you have increased distance there, you may have an unstable situation. And then the Tasmanian view is essentially a scapula wide view with cross body adduction. And if you if you get a significant crossover, that's an indication that they probably have some anterior posterior instability. What about treatment? Well, grades one and two we would all agree that are non-operative. Grade four through six. Pretty much everybody agrees that you operate on those. But it's the threes that are controversial and they're still controversial. They'll probably always be controversial. So some other factors that I like to consider is a patient's age. What's their profession their activity level. What's their favorite sports. What's their medical comorbidities. Scapula kinematics. Do we have some long term outcomes with scapula kinematics or changes? We probably do. I don't know if we fully understand them. And then cosmesis is a very minor concern. So the treatment options, you could observe them. You can just do rehabilitation. You can operate early and we'll talk about what early means. And then or you could do delayed operative intervention with a reconstructive procedure. So procedures have typically been either kind of mechanical in nature or biologic in nature, and some procedures have been a combination of the two. So as far as biologic or soft tissue procedures, those have included ligament reconstruction such as the weaver Dunn or the accr. The anatomic coracoclavicular reconstruction that Doctor Mazzocca popularized other mechanical fixation methods have been K-wires. Probably not a good idea. Screw fixation into the coracoid hook plates. Coracoid cerclage procedures. Tightrope. Twintail. Tightropes. The device, called lockdown, is a mechanical device. And then the dog bone is a mechanical device that I'll discuss primarily. What about combination procedures? Mechanical and soft tissue? Well, the GraftPro was out for a while, but the complication rate was high because it's got a really large hole that you drill. So that's not out anymore. And what I find to be my procedure of choice is this. Which is a is a dog bone for mechanical fixation, and then allograft or soft tissue augmentation. I'll go through that. So it's important that that that you monitor the size of the tunnels, the size of the tunnels really makes a huge difference. And I'll show you some data on that. Here's a little bit if you go from a four millimeter tunnel to a 2.4mm tunnel, you reduce the percentage of bone loss by 64%, so you take away much less bone. If you look at the strength of the constructs, a dog bone with two FiberTape is almost 1400 newtons load to failure, whereas native ligaments are about 724 newtons. What about fracture risk? Well, well, Peter Millett's group looked at the fracture risk of tunnels in the clavicle specifically. He reproduced what essentially is the ACC CRx type of technique, where you have two clavicle bone tunnels, and he found about a 31% decrease in the clavicle strength to to bending loads, whereas the dog bone type of fixation with a 2.4mm tunnel, you only had a 3.8% decrease in your strength of the bone. There's been another study. I'm not sure if it's published yet, but it should be soon. It's accepted. It looks at the coracoid tunnel and a four millimeter coracoid tunnel. When they pulled these things to failure, 100% of them failed via the coracoid fracturing. Whereas if they looked at the 2.4mm tunnel group, they all failed via the the conjoined tendon pulling off the bone. They did not fracture. So let's look at AC joint reconstruction. This is a cadaveric model here. And we'll just go through the procedure. You can try this in the lab I encourage you to and we'll look at the animation. First you place the drill guide through an anterior portal. You drill through the clavicle through the coracoid with a cannulated drill. You take out the inner portion of the cannulation and then you pass a nitinol wire Pull that out your anterior portal, and then you deliver your construct in a retrograde fashion, through your coracoid, through your clavicle, and then you seat that coracoid dog bone. Finally, you do your reduction. You put the clavicle dog bone, you tie it, and that's your mechanical dog bone fixation. Here we'll look at a right shoulder posterior viewing portal first. And then the antero-superolateral portal is a is a very important portal that you're going to use for the majority of the procedure. It's going to be your working portal or your visualization portal primarily. So you make that right over the roof of the biceps. I usually leave that spinal needle in place, and then you're going to clear the subcoracoid space. You can work around the middle glenohumeral ligament if you like. This is a cadaver demonstration. So I remove the middle glenohumeral ligament so we could really see. And then you'll find the coracoid just anterior to the superior border of the clavicle. It's something I really encourage you to try to do in the lab, because why not? You know, you're not going to mess anything up in the lab. And so. So it's nice. A lot of people are scared of that area from a neurovascular standpoint. But as long as you find that coracoid and you stay on bone, you're fine. Then you'll use a 70 degree scope. I'll kind of look around the corner, and I really am trying to work toward the base of the coracoid and clear out the base of the coracoid. Before I leave that posterior visualization portal, I'm going to place an anterior portal, and it's important to use a malleable cannula in. The passport is perfect for this area because this is going to be your instrumentation portal. So now we'll visualize with a 30 degree from the ASL. And then we'll work from the anterior portal. You can take a probe, do this in the lab, take a probe and just kind of palpate the tip of the coracoid. You'll notice that it's only about 15. The neck is about 20mm from medial to lateral. But the base is pretty large usually 30 or 35mm. And so that's why you really want to be drilling at the base of the coracoid center of your clavicle incision about three centimeters. Again from the AC joint. Dissect down. Dissect your anterior and Anterior and posterior clavicle. And then place your drill guide. There's another drill guide I'll show you in a minute, which I like a little bit better than this one, but place your drill guide underneath. Make sure you're pushing it toward the base of the coracoid. Then you'll drill through your clavicle, through your coracoid. If you do this right, you ought to feel for cortices as you're drilling. If you don't feel for cortices, you're probably off somewhere. So before you buy this, you know it's only a 2.4mm guide pin. So before you for sure buy it, make sure that you've got enough bone, both medial and lateral to this drill. Then you'll take the center out. Pass your nitinol through it. Now I always switch out this nitinol to a FiberLink. Okay, I had one case where I was trying to pull the construct back retrograde with a nitinol. The nitinol broke and that was frustrating. I had to start essentially start over, so I always switch it out to a FiberLink. I've never broken a FiberLink before and then I'll use that to this case. I didn't, but this is a cadaver case. But but I'll use that FiberLink to shuttle these FiberTape sutures. Up through the coracoid tunnel and the clavicle tunnel. Then I'll take a seat. That dog bone underneath the coracoid. Now, there's a laser line that you should line up with the axis of the coracoid. And that'll that's that'll allow it to seat the best way possible. The final step is to reduce your distal clavicle to clip your clavicle dog bone. Click your clip your FiberTape into there and then tie those down. And and that's that's essentially the procedure. So chronic what's chronic. Well there's always a race. There's a race between biologic healing and mechanical failure. One of those things is going to happen first. So what is chronic. Is it three months. Is it four weeks. Is it one week? I don't think we know for sure, but I, I would say that myself, as well as all the other fellows, are definitely leaning toward less and less time. For me, it's about two weeks now. If I can get to somebody in the first two weeks, I'll do an isolated dog bone. I've had good results with that. If it's past two weeks, I'll add an allograft. Some guys are adding an allograft every time. I don't think there's anything wrong with that either. So allograft, let me show you a little bit about that. Arthrex has come up with some nice instrumentation to help you with the arthroscopic allograft passage, specifically this curved coracoid parser and the flexible obturator. Definitely try these. The curved parser. What I do is I place the parser anterior to the clavicle, then excuse me, anterior clavicle, medial to the coracoid. You'll feel the coracoid right underneath that clavicle, and then you just bounce yourself medial to the coracoid. Go through the pectoralis minor, stay right on the bone, and then you pass a FiberStick through that that that obturator. Then you'll then you'll grab the FiberStick from anterior to the clavicle and lateral to the coracoid. And now you have your suture passed underneath the coracoid. You'll utilize that to shuttle this flexible obturator, and then you then you just tie your graph to the end of the flexible arbitrator, and now you have your graph underneath the coracoid. Now you want one of those limbs behind the coracoid. And if you want to reproduce the anatomy as best as possible, you want to take your medial limb and bring it behind the coracoid. And then I just tie all that over top of the clavicle. Usually it ties over almost exactly where your dog bone was. So I'll tie one of the sutures of the dog bone. Then I'll do the allograft wrap, and then I'll tie the second suture of the dog bone. So here's a case where we're going to we're going to demonstrate this. We're going to we're going to go just anterior the clavicle. Now we're going to visualize through our ASL port or our anterior portal. We're going to pass that underneath the coracoid. Fiberstick goes through there. And then we'll grab that. We'll grab that FiberStick first. We'll grab it through our ASL portal. And then we'll reach down and pull it up. Again. This one goes anterior to the clavicle and lateral to the coracoid. We'll utilize that to shuttle the flexible obturator. Here comes the flexible obturator. You can cycle that several times. That can be helpful just to just to widen those tunnels a little bit. And then you tie the graph to the end of the flexible arbitrator. Or tie the whip sutures from the graft. And then the graft usually passes very nicely with that. So here's a patient with he's about six months post ATV accident. Obvious deformity. The deformity actually gets worse when he tries to elevate the shoulder. And if you look at his clinical exam in the operating room, you can see how much both anterior posterior instability he has. As well as superior, inferior instability. And he's about six months out now from this from this injury. So his AP instability was pretty significant. So here it is. Once I've made the incision, I made it a little larger clavicle incision because I'm going to do this thing called an internal brace. Okay. Gordon McKay has, has, has talked a lot about the internal brace. I have become a firm believer on the internal brace for AC joint injuries and what we did. So we wrapped the graft. We did the dog bone, we wrapped the grafts around the clavicle. We tied those to one another. And then you can see those FiberTape sutures. There's there's one going here between anterior clavicle, anterior acromion. And then and then I took that limb and then I brought it posteriorly, and I, and I tied it into the posterior distal clavicle as well. And you can see that almost completely eliminates your anterior posterior motion. So how do you how do you rehab these people? I wish this guy was at my gym because I love this guy. I don't know who he is, but he's awesome. So I rehab him very, very slowly for about six weeks. I allow essentially no motion. The next six weeks, I'll let them do progress to some active motion. And then then I'll progress to strengthening full release. Not until about six months. And the reason I go slow is because biology really needs to win this race. If you remember the motion that you got there, you got some translation, you got some rotation. So you want to minimize all this motion until those soft tissues have had time to fill in. My clinical results have been good. With about 30 cases. All the shoulder scores have improved, about two thirds have maintained a perfect reduction, and about one third have settled into a type two and some pearls to minimize that loss of reduction is to make sure you take out all the slack in the system. Before you tie this thing down, make sure your tunnels are well positioned. They should be straight up and down. If you have a lot of tilt to the tunnels, then you're probably going to get some loosening and some tunnel widening, if in doubt, and maybe all the time use allograft. I think that helps to minimize bone fractures. That's with these smaller tunnels. That's essential. And then the tunnel widening issue again, I think that has a lot to do with tunnel positioning. Why do I use a dogbone? It's very strong. It's 1400 Newtons. Load to failure. It's easy. You don't need a second surgery and it doesn't have a lot of complications. You minimize the holes both in number and size. You know, there's a lot of complications with all these procedures. And we want to minimize that. Here's where a needed a second surgery to remove the implant. And it ate through the acromion. So in in and of itself. On a side note, if you want to try the dogbone, it is fantastic for these type two distal clavicle fractures. Okay, this this girl is about 18. She might have been 20 by this time. She had distal clavicle fracture. She started bawling when I said we might have to do an incision and a clavicle plate and then might have to remove the clavicle plate. So I said, well, let's try something else. And we did the dog bone, and it turned out great. She, she wears her bra strap. You can see her bra strap goes directly over top of there. Although she does have a knot stack underneath there. It doesn't bother her a bit.

The Dog Bone Technique for AC Joint Reconstruction

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