Knee

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Interference screws are constructed using the high quality that is synonymous with the Arthrex name. The complete family includes biocomposite interference screws (comprised of 30% biphasic calcium phosphate and 70% PLDLA), PEEK interference screws (made from PEEK-OPTIMA™), metal interference screws (made from titanium for femoral and tibial fixation of soft-tissue or bone).
 
PEEK-OPTIMA is a trademark of Invibio.

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Human

FastThread™ Interference Screws A New Turn in ACL Fixation

SlapDriver Interference Screwdriver

Matthew J. Matava, MD (St. Louis, MO), performs a clinical demonstration of a BTB ACL reconstruction using BioComposite FastThread™ interference screws combined with FiberTape® suture for the InternalBrace™ technique.
The InternalBrace surgical technique is intended only to augment the primary repair/reconstruction by expanding the area of tissue approximation during the healing period and is not intended as a replacement for the native ligament. The InternalBrace technique is for use during soft tissue-to-bone fixation procedures and is not cleared for bone-to-bone fixation.

video

BTB Reconstruction Using FastThread™ Screws and the InternalBrace™ Technique

So here you are preparing the notch for an ACL reconstruction. We've already harvested the patellar tendon graft, and if you notice, there is no leakage of fluid coming out of our harvest site. Okay, so we're ready to drill our tibial tunnel. The question becomes how do you know how to set your tibial guide? In general, I like to set the guide such that it's at 55 degrees. Okay, that seems to work for most patients. Now, a key to this operation to me, when you're using two Bone-tendon-bone Autograft two bone plugs is you have to set your tibial guide length. Otherwise you're at risk for having your tibial bone plug sticking out of the femur. Okay, that's a problem. You can't use interference fixation. So how do you know how to do this? You can't just slide this up to the tibia because your wrist shorten the tunnel relative to the length of the graft, and then it'll be sticking out. This is especially important if you use an allograft, or if you have a patient who's five foot five and your allograft tendon is coming from a person who's six foot six, it's going to be way too long, so I have a formula I can use for that. So we'll do is we'll take the graft in total. Here's the length of the graft. So this graph measures about 85mm from tip to tip. The femoral bone plug measures 25mm. So I take 85 of the total length of the graph -25. That's 60mm which is what the intra-articular portion of the graph should be. And the tibial portion of the graph that's 60mm. About 25mm of that is going to be for the intra-articular portion of the graph. So I'll subtract 25mm from that 60mm. That leaves 35mm at a minimum that I need for the tibial tunnel. I had to cheat a little bit. I'll add to 40mm that way. I have no concerns that the tibial bone plug will be sticking out of the tibial tunnel. So I'll take our guide. We've already set to the 55 degree angle, and we'll set the tibial side to 40mm right there. That means our tibial length is 40mm. And by doing that you should have a bone graph that does not stick out of the tibia. That's customized for every individual patient. So we're drilling our tibial tunnel. We have our guide set such that the pin comes out just medial to midline, in line with the posterior aspect of the anterior horn of the lateral meniscus. So here's our pin. There's our anterior horn of the lateral meniscus. The posterior aspect of it. If you're concerned about the amount of impingement you have, you can take your knee in full extension under the scope and make sure there's no impingement of the notch. So that looks relatively acceptable. Typically this is going to be about 7 to 10mm from the PCL. Then we'll Overeem with a ten millimeter reamer. It's important to use a drill guide for this in a real patient so that you don't cut the skin. We'll take a Ranger to open up the aperture of our tibial tunnel to get all this soft tissue out of the way, because sometimes that prohibits the graft from being pulled into the joint. All right, so there's our tibial tunnel. And again, if you're concerned when you're first starting to do this, whether or not you have impingement, you can put can put your shaver up the tibia and extend the knee. And show there's no impingement. There's full extension. There's no impingement of our graft. So here's our trans our Am portal drill guide on the femoral, if you notice, has a little curve to it that allows it to go around the back of the intercondylar notch via the Am portal. So we'll hyper flex the knee to at least 105 degrees, preferably more. If you don't hyper flex the knee, then what happens is you risk blowing out the back wall when you drill your tunnel. So here's my finger guide is up against the back of the notch. I'm trying to go through the center of the Am portal for a single bundle reconstruction, and we're using a four millimeter spade tip guide wire because we're going to be using the TightRope device with the internal brace. Once you're through that tibial tibial cortex, we'll take our guide out and we'll pull this back. This acts as a depth gauge. You see there's markings on it. Usually most males are between 32 to. To 38mm in length. And here my spade tip is up against the far cortex. And that's about 36 maybe 37mm. You see there's the four on it right there. Okay. So that shows us how wide our femoral condyle is. Now we will drill this out through the skin. Great. Now we will take our low profile femoral reamer. It's very important that you clean out all the fat pad before you do this. If you notice, we've already done a good job of cleaning the fat pad. But I still want to make sure that there is no chance that I'm going to hit the medial femoral condyle with my femoral reamer. And that's the reason why Arthrex has devised this low profile reamer, because it works really well in avoiding that estrogenic complication. So that's pretty well cleaned out. You can use an 11 blade as well, but for the purposes of today did a good job with the shaver. Here's our reamer. There's a black line right here. And that black line is parallel in line with the blade. So you So you know, when this blade is inside the skin, you can't see any longer. You know the orientation because you can follow the orientation of the black line. Okay. You should always see the black line because you know that this is vertical. If this is vertical, it's not going to hit the femoral condyle. So we'll put the blade in. And as you're watching it arthroscopically sometimes if you lift your hand up a little bit, that helps it go in a little bit easier. Pass the fat. There you go. There it is. Nice and vertical. We completely missed our femoral condyle, which is way over there. Okay. But again we can still see our black line is vertical over here. So we've done a good job of avoiding that. So we have our low profile reamer in the joint. We've already prepared our notch. Now when we start to ream, I like to start the reamer off the bone, because I don't like to have the reamer on the bone, because I don't want to have any sort of risk of damage in the blade. We'll start the reaming and then we'll hit the bone. Now our femoral bone plug measures 25mm. I like to drill it two millimeters deeper than the depth of the bone plug. Here's our tunnel. Our back wall is intact. Looks good. We'll take the wire out. We have a FiberWire suture that we're shuttling through. We'll pull this to the tunnel until the loop is seen. Then we'll go through our tibial tunnel, grab our suture and pull it through. And that will be our passing suture. So here is our internal brace. Here's the button that will be deployed on the lateral femoral cortex. And if you remember, we measured our interosseous length of the lateral femoral condyle as being 37mm. We've made a mark from the tip of that TightRope anchor to 37mm. That's the way we know when the metal button is fully gone through the femoral condyle. Here's our passage. Suture. Now we're going to be passing up our internal brace suture as well as our Graf suture. So the internal brace is the TigerWire and the ACL graft is the blue suture. So Now in sequence, we're going to pass our TigerWire up that has the TightRope on it. And now a little Perl here will stop, and we'll put the scope in the Am portal so we can see exactly when that button goes out of the bone, and we can see where our mark is. Now typically I will do this under Fluoroscopic visualization. So I know exactly when my TightRope device has deployed on the lateral femoral cortex. Here's our mark. So we know we're very close. And sometimes you can feel a little pop once it goes through the femoral bone. Okay. It looks like he's probably through there. So our TightRope has been deployed. It's secure. We're pulling traction distally on that TightRope. It's very solid, as you can see. Once I get a pull, they're nice and solid there. So we feel good about that. We pass our BTB graft anterior to the internal brace, use a probe to help pull and change the direction of force of the as we pull the BTB up. So here it is in the femoral tunnel. Again, we made the graft big enough so that it should go very well. Now it's very key here when you're putting your BTB bone plug in the femur that your cancellous surface is facing anterior. Here's our mark we made earlier so we know how far to pull it up. But we're going to guide it in with this probe and pull it up. And we have to make sure that it's going in the tibial side as well. And there it goes. And it dunked in very nicely. All right. So we're going to use a Notcher. We'll put the Notcher. You want to drop your hands as much as you can so that you're hitting the bone of the tunnel. Great. Now we'll take our nitinol wire and our tap so we have a protective sheath over our tap, and we want to tap our tunnel to accommodate the screw. Again, the protective sheath protects the graft. It also protects the PCL, so there's no genetic damage from the tap. Now we want to grab tension on our sutures here. Approximately. We'll put our sheath up against the graft. Here's our bow composite FastThread screw. A nice squeak means our fixation is good. We're now line to line, and we'll take our insert off. Now, for a ten millimeter size tunnel and a ten millimeter bone plug, I like to go down two sizes on our interference screw. That's an eight. There's some research that shows you can go down to even a seven or perhaps a six. I get the best fixation, I feel, with the most ease of insertion. If I go two sizes down, if I'm using an allograft, I'll only go one size down on our screw. But there's our bone plug. There's our mark. We put make sure we're fully deployed into the tunnel. There's our screw, nice and flush with the bone. One final test. Make sure our fixation is good. We'll take the distal end of the graft. We'll pull, and then we'll cycle the knee from 0 to 9 degrees multiple times. Fully tension the graft. Make sure there's there's no impingement. We also want to make sure that there's good isometrics. So what I have is I have my fingertip on the aperture of the tunnel as he's cycling. If there's non-isometric placement on the graph, we'll feel these sutures go up or down the tunnel, respectively. You can have about two millimeters of play of the sutures going up and down the tunnel. In this particular situation, there was good tension throughout, but I always want to do that after you put your femoral screw in. So now we'll put our distal fixation in of our internal brace. We're gonna go just distal to our tibial tunnel. I want to clear the soft tissues off just for ease of insertion of the SwiveLock. So here is our tibial tunnel above. And if you notice, our tibial bone plug is not sticking out of the tibia. Okay. So we did our calculations earlier and we have good placement of the tunnel and good placement of bone plug without it coming out of the tunnel. So we'll take our spade tip pin go just distal to our tibial tunnel. This has a positive stop. We'll then tap it. So we've separated our BTB sutures and wire from our internal brace sutures. We've threaded the sutures through our SwiveLock. We're going to take our tap out. We're going to take the knee in full extension with our anchor ready to be deployed. And there's our anchor fully deployed. Now the question comes in how much tension should you apply? Really you can only apply so much tension to this suture as you're inserting your your anchor. By placing the in full extension, we're not going to entrap the knee or prevent full extension. We're starting out in a fully extended position when we put our internal brace in. Here's our BTB graft. Here's our nitinol wire. It's anterior because remember that's where our cancellous bone is. Okay. But you always have to make sure that your wire is in the tunnel and confirmed by viewing arthroscopically. It is not anterior to the tibia as can be done if you're not careful in this regard. So we'll take our interference screw and tap. Now, as I said on the femoral side, I'll use a screw two sizes down in the tunnel or the bone plug size on the tibial side. I'll go down one size because again the bone is a little bit softer. So in this situation we're going to use a screw that's one size smaller. Now we'll put the knee in full extension. Again we have two distal sutures and one wire. That way we know we're not going to lose fixation. Okay. Go ahead. If you notice, our bone plug is not sticking out of the tibia because we measured our tibial drill guide to ensure that doesn't happen. We have very good purchase on our screw. Here's our final grab construct. Looks nice and taut. Take the knee and full extension remains nice and taut. There's absolutely zero impingement of the notch. And again, keep in mind the graft and the internal brace were fixed independently of one another. The internal brace, which you can see behind the graft, acts as a seatbelt of sorts to protect the graft through extremes of force. As a backup. But our graft, again is doing the primary restraint as our final product.

Interference Screws

Child (D)

Secondary (C)